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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Capacitance</span></span>
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</style><div role="note" class="hatnote navigation-not-searchable">For capacitance of blood vessels, see <a href="Compliance_(physiology)" title="Compliance (physiology)">Compliance (physiology)</a>.</div>
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</style><table class="infobox"><tbody><tr><th scope="row" class="infobox-label"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;">Common symbols</div></th><td class="infobox-data"><span class="texhtml"><i>C</i></span></td></tr><tr><th scope="row" class="infobox-label"><a href="SI_unit" class="mw-redirect" title="SI unit">SI unit</a></th><td class="infobox-data"><a href="Farad" title="Farad">farad</a></td></tr><tr><th scope="row" class="infobox-label"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;">Other units</div></th><td class="infobox-data">μF, nF, pF</td></tr><tr><th scope="row" class="infobox-label">In <a href="SI_base_unit" title="SI base unit"><span class="wrap">SI base units</span></a></th><td class="infobox-data">F = A<sup>2</sup> s<sup>4</sup> kg<sup>−1</sup> m<sup>−2</sup></td></tr><tr><th scope="row" class="infobox-label"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;">Derivations from<br>other quantities</div></th><td class="infobox-data"><i>C</i> = <b><a href="Electric_charge" title="Electric charge">charge</a></b> / <b><a href="Voltage" title="Voltage">voltage</a></b></td></tr><tr><th scope="row" class="infobox-label"><a href="Dimensional_analysis#Formulation" title="Dimensional analysis">Dimension</a></th><td class="infobox-data"><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\mathsf {L}}^{-2}{\mathsf {M}}^{-1}{\mathsf {T}}^{4}{\mathsf {I}}^{2}}">
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<annotation encoding="application/x-tex">{\displaystyle {\mathsf {L}}^{-2}{\mathsf {M}}^{-1}{\mathsf {T}}^{4}{\mathsf {I}}^{2}}</annotation>
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</style><table class="sidebar sidebar-collapse nomobile nowraplinks em-sidebar"><tbody><tr><th class="sidebar-title"><a href="Electromagnetism" title="Electromagnetism">Electromagnetism</a></th></tr><tr><td class="sidebar-image"></td></tr><tr><td class="sidebar-content hlist">
<ul><li><a href="Electricity" title="Electricity">Electricity</a></li>
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<li><a href="History_of_electromagnetic_theory" title="History of electromagnetic theory">History</a></li>
<li><a href="Computational_electromagnetics" title="Computational electromagnetics">Computational</a></li>
<li><a href="List_of_textbooks_in_electromagnetism" title="List of textbooks in electromagnetism">Textbooks</a></li>
<li><a href="List_of_electrical_phenomena" title="List of electrical phenomena">Phenomena</a></li></ul></td>
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<ul><li><a href="Charge_density" title="Charge density">Charge density</a></li>
<li><a href="Electrical_conductor" title="Electrical conductor">Conductor</a></li>
<li><a href="Coulomb's_law" title="Coulomb's law">Coulomb law</a></li>
<li><a href="Electret" title="Electret">Electret</a></li>
<li><a href="Electric_charge" title="Electric charge">Electric charge</a></li>
<li><a href="Electric_dipole_moment" title="Electric dipole moment">Electric dipole</a></li>
<li><a href="Electric_field" title="Electric field">Electric field</a></li>
<li><a href="Electric_flux" title="Electric flux">Electric flux</a></li>
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<li><a href="Electrostatic_discharge" title="Electrostatic discharge">Electrostatic discharge</a></li>
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<li><a href="Permittivity" title="Permittivity">Permittivity</a></li>
<li><a href="Polarization_density" title="Polarization density">Polarization</a></li>
<li><a href="Electric_potential_energy" title="Electric potential energy">Potential energy</a></li>
<li><a href="Static_electricity" title="Static electricity">Static electricity</a></li>
<li><a href="Triboelectric_effect" title="Triboelectric effect">Triboelectricity</a></li></ul></div></div></td>
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<ul><li><a href="Amp%C3%A8re's_circuital_law" title="Ampère's circuital law">Ampère's law</a></li>
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<li><a href="Magnetic_moment" title="Magnetic moment">Magnetic dipole</a></li>
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<li><a href="Permeability_(electromagnetism)" title="Permeability (electromagnetism)">Permeability</a></li>
<li><a href="Right-hand_rule#Electromagnetism" title="Right-hand rule">Right-hand rule</a></li></ul></div></div></td>
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<ul><li><a href="Bremsstrahlung" title="Bremsstrahlung">Bremsstrahlung</a></li>
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<li><a href="Lenz's_law" title="Lenz's law">Lenz's law</a></li>
<li><a href="Li%C3%A9nard%E2%80%93Wiechert_potential" title="Liénard–Wiechert potential">Liénard–Wiechert potential</a></li>
<li><a href="London_equations" title="London equations">London equations</a></li>
<li><a href="Lorentz_force" title="Lorentz force">Lorentz force</a></li>
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<li><a href="Maxwell_stress_tensor" title="Maxwell stress tensor">Maxwell tensor</a></li>
<li><a href="Poynting_vector" title="Poynting vector">Poynting vector</a></li>
<li><a href="Synchrotron_radiation" title="Synchrotron radiation">Synchrotron radiation</a></li></ul></div></div></td>
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<ul><li><a href="Alternating_current" title="Alternating current">Alternating current</a></li>
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<li><a href="Direct_current" title="Direct current">Direct current</a></li>
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<li><a href="Inductance" title="Inductance">Inductance</a></li>
<li><a href="Joule_heating" title="Joule heating">Joule heating</a></li>
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<li><a href="Network_analysis_(electrical_circuits)" title="Network analysis (electrical circuits)">Network analysis</a></li>
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<ul><li><a href="AC_motor" title="AC motor">AC motor</a></li>
<li><a href="DC_motor" title="DC motor">DC motor</a></li>
<li><a href="Electric_machine" title="Electric machine">Electric machine</a></li>
<li><a href="Electric_motor" title="Electric motor">Electric motor</a></li>
<li><a href="Gyrator%E2%80%93capacitor_model" title="Gyrator–capacitor model">Gyrator–capacitor</a></li>
<li><a href="Induction_motor" title="Induction motor">Induction motor</a></li>
<li><a href="Linear_motor" title="Linear motor">Linear motor</a></li>
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<li><a href="Permeance" title="Permeance">Permeance</a></li>
<li><a href="Magnetic_complex_reluctance" title="Magnetic complex reluctance">Reluctance (complex)</a></li>
<li><a href="Magnetic_reluctance" title="Magnetic reluctance">Reluctance (real)</a></li>
<li><a href="Rotor_(electric)" title="Rotor (electric)">Rotor</a></li>
<li><a href="Stator" title="Stator">Stator</a></li>
<li><a href="Transformer" title="Transformer">Transformer</a></li></ul></div></div></td>
</tr><tr><td class="sidebar-content hlist">
<div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="color: var(--color-base)"><div class="sidebar-list-title-c"><a href="Covariant_formulation_of_classical_electromagnetism" title="Covariant formulation of classical electromagnetism">Covariant formulation</a></div></div><div class="sidebar-list-content mw-collapsible-content hlist">
<ul><li><a href="Electromagnetic_tensor" title="Electromagnetic tensor">Electromagnetic tensor</a></li>
<li><a href="Classical_electromagnetism_and_special_relativity" title="Classical electromagnetism and special relativity">Electromagnetism and special relativity</a></li>
<li><a href="Four-current" title="Four-current">Four-current</a></li>
<li><a href="Electromagnetic_four-potential" title="Electromagnetic four-potential">Four-potential</a></li>
<li><a href="Mathematical_descriptions_of_the_electromagnetic_field" title="Mathematical descriptions of the electromagnetic field">Mathematical descriptions</a></li>
<li><a href="Maxwell's_equations_in_curved_spacetime" title="Maxwell's equations in curved spacetime">Maxwell equations in curved spacetime</a></li>
<li><a href="Relativistic_electromagnetism" title="Relativistic electromagnetism">Relativistic electromagnetism</a></li>
<li><a href="Electromagnetic_stress%E2%80%93energy_tensor" title="Electromagnetic stress–energy tensor">Stress–energy tensor</a></li></ul></div></div></td>
</tr><tr><td class="sidebar-content hlist">
<div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="color: var(--color-base)"><div class="sidebar-list-title-c">Scientists</div></div><div class="sidebar-list-content mw-collapsible-content hlist">
<ul><li><a href="Andr%C3%A9-Marie_Amp%C3%A8re" title="André-Marie Ampère">Ampère</a></li>
<li><a href="Jean-Baptiste_Biot" title="Jean-Baptiste Biot">Biot</a></li>
<li><a href="Charles-Augustin_de_Coulomb" title="Charles-Augustin de Coulomb">Coulomb</a></li>
<li><a href="Humphry_Davy" title="Humphry Davy">Davy</a></li>
<li><a href="Albert_Einstein" title="Albert Einstein">Einstein</a></li>
<li><a href="Michael_Faraday" title="Michael Faraday">Faraday</a></li>
<li><a href="Hippolyte_Fizeau" title="Hippolyte Fizeau">Fizeau</a></li>
<li><a href="Carl_Friedrich_Gauss" title="Carl Friedrich Gauss">Gauss</a></li>
<li><a href="Oliver_Heaviside" title="Oliver Heaviside">Heaviside</a></li>
<li><a href="Hermann_von_Helmholtz" title="Hermann von Helmholtz">Helmholtz</a></li>
<li><a href="Joseph_Henry" title="Joseph Henry">Henry</a></li>
<li><a href="Heinrich_Hertz" title="Heinrich Hertz">Hertz</a></li>
<li><a href="John_Hopkinson" title="John Hopkinson">Hopkinson</a></li>
<li><a href="Oleg_D._Jefimenko" title="Oleg D. Jefimenko">Jefimenko</a></li>
<li><a href="James_Prescott_Joule" title="James Prescott Joule">Joule</a></li>
<li><a href="Lord_Kelvin" title="Lord Kelvin">Kelvin</a></li>
<li><a href="Gustav_Kirchhoff" title="Gustav Kirchhoff">Kirchhoff</a></li>
<li><a href="Joseph_Larmor" title="Joseph Larmor">Larmor</a></li>
<li><a href="Emil_Lenz" title="Emil Lenz">Lenz</a></li>
<li><a href="Alfred-Marie_Li%C3%A9nard" title="Alfred-Marie Liénard">Liénard</a></li>
<li><a href="Hendrik_Lorentz" title="Hendrik Lorentz">Lorentz</a></li>
<li><a href="James_Clerk_Maxwell" title="James Clerk Maxwell">Maxwell</a></li>
<li><a href="Franz_Ernst_Neumann" title="Franz Ernst Neumann">Neumann</a></li>
<li><a href="Georg_Ohm" title="Georg Ohm">Ohm</a></li>
<li><a href="Hans_Christian_%C3%98rsted" title="Hans Christian Ørsted">Ørsted</a></li>
<li><a href="Sim%C3%A9on_Denis_Poisson" title="Siméon Denis Poisson">Poisson</a></li>
<li><a href="John_Henry_Poynting" title="John Henry Poynting">Poynting</a></li>
<li><a href="William_Ritchie_(physicist)" title="William Ritchie (physicist)">Ritchie</a></li>
<li><a href="F%C3%A9lix_Savart" title="Félix Savart">Savart</a></li>
<li><a href="George_Singer" title="George Singer">Singer</a></li>
<li><a href="Charles_Proteus_Steinmetz" title="Charles Proteus Steinmetz">Steinmetz</a></li>
<li><a href="Nikola_Tesla" title="Nikola Tesla">Tesla</a></li>
<li><a href="J._J._Thomson" title="J. J. Thomson">Thomson</a></li>
<li><a href="Alessandro_Volta" title="Alessandro Volta">Volta</a></li>
<li><a href="Wilhelm_Eduard_Weber" title="Wilhelm Eduard Weber">Weber</a></li>
<li><a href="Emil_Wiechert" title="Emil Wiechert">Wiechert</a></li></ul></div></div></td>
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<p><b>Capacitance</b> is the ability of an object to store <a href="Electric_charge" title="Electric charge">electric charge</a>. It is measured by the change in charge in response to a difference in <a href="Electric_potential" title="Electric potential">electric potential</a>, expressed as the ratio of those quantities. Commonly recognized are two closely related notions of capacitance: <i>self capacitance</i> and <i>mutual capacitance</i>.<sup id="cite_ref-Harrington_2003_1-0" class="reference"><a href="#cite_note-Harrington_2003-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page / location: 237–238">: 237–238 </span></sup> An object that can be electrically charged exhibits self capacitance, for which the electric potential is measured between the object and ground. Mutual capacitance is measured between two components, and is particularly important in the operation of the <a href="Capacitor" title="Capacitor">capacitor</a>, an elementary <a href="Linear_circuit" title="Linear circuit">linear</a> <a href="Electronic_component" title="Electronic component">electronic component</a> designed to add capacitance to an <a href="Electric_circuit" class="mw-redirect" title="Electric circuit">electric circuit</a>.
</p><p>The capacitance between two <a href="Electrical_resistance_and_conductance" title="Electrical resistance and conductance">conductors</a> depends only on the geometry; the opposing surface area of the conductors and the distance between them; and the <a href="Permittivity" title="Permittivity">permittivity</a> of any <a href="Dielectric" title="Dielectric">dielectric</a> material between them. For many dielectric materials, the permittivity, and thus the capacitance, is independent of the potential difference between the conductors and the total charge on them.
</p><p>The <a href="SI" class="mw-redirect" title="SI">SI</a> unit of capacitance is the <a href="Farad" title="Farad">farad</a> (symbol: F), named after the English physicist <a href="Michael_Faraday" title="Michael Faraday">Michael Faraday</a>.<sup id="cite_ref-NSW_2-0" class="reference"><a href="#cite_note-NSW-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> A 1 farad capacitor, when charged with 1 <a href="Coulomb" title="Coulomb">coulomb</a> of electrical charge, has a potential difference of 1 <a href="Volt" title="Volt">volt</a> between its plates.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> The reciprocal of capacitance is called <a href="Elastance" title="Elastance">elastance</a>.
</p>
<meta property="mw:PageProp/toc">
<div class="mw-heading mw-heading2"><h2 id="Self_capacitance">Self capacitance</h2></div>
<p>In discussing electrical circuits, the term <i>capacitance</i> is usually a shorthand for the mutual capacitance between two adjacent conductors, such as the two plates of a capacitor. However, every isolated conductor also exhibits capacitance, here called <i>self capacitance</i>. It is measured by the amount of electric charge that must be added to an isolated conductor to raise its <a href="Electric_potential" title="Electric potential">electric potential</a> by one unit of measurement, e.g., one <a href="Volt" title="Volt">volt</a>.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> The reference point for this potential is a theoretical hollow conducting sphere, of infinite radius, with the conductor centered inside this sphere.
</p><p>Self capacitance of a conductor is defined by the ratio of charge and electric potential:
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C={\frac {q}{V}},}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>C</mi>
<mo>=</mo>
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<mi>q</mi>
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<mo>,</mo>
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<annotation encoding="application/x-tex">{\displaystyle C={\frac {q}{V}},}</annotation>
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where
</p>
<ul><li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle q}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>q</mi>
</mstyle>
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<annotation encoding="application/x-tex">{\textstyle q}</annotation>
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</math></span><img src="./a32efd4de244331181b8fa97862015251f65da5f.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:1.07ex; height:2.009ex;" alt="{\textstyle q}" loading="lazy"></span> is the charge held,</li>
<li><big><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle V={\frac {1}{4\pi \varepsilon _{0}}}\int {\frac {\sigma }{r}}\,dS}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>V</mi>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>1</mn>
<mrow>
<mn>4</mn>
<mi>π<!-- π --></mi>
<msub>
<mi>ε<!-- ε --></mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>0</mn>
</mrow>
</msub>
</mrow>
</mfrac>
</mrow>
<mo>∫<!-- ∫ --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mi>σ<!-- σ --></mi>
<mi>r</mi>
</mfrac>
</mrow>
<mspace width="thinmathspace"></mspace>
<mi>d</mi>
<mi>S</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle V={\frac {1}{4\pi \varepsilon _{0}}}\int {\frac {\sigma }{r}}\,dS}</annotation>
</semantics>
</math></span><img src="./cc842c312f8260c957eac5dd4557f5fe4a13f643.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.671ex; width:16.154ex; height:4.009ex;" alt="{\textstyle V={\frac {1}{4\pi \varepsilon _{0}}}\int {\frac {\sigma }{r}}\,dS}" loading="lazy"></span></big> is the electric potential,</li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle \sigma }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>σ<!-- σ --></mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle \sigma }</annotation>
</semantics>
</math></span><img src="./8ca336f17488923d11206e131f7eb2a569e8dde2.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.33ex; height:1.676ex;" alt="{\textstyle \sigma }" loading="lazy"></span> is the surface charge density,</li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle dS}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
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<mi>d</mi>
<mi>S</mi>
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<annotation encoding="application/x-tex">{\textstyle dS}</annotation>
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</math></span><img src="./a4d5150354609d35245fc96ee526f91f45d66838.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.715ex; height:2.176ex;" alt="{\textstyle dS}" loading="lazy"></span> is an infinitesimal element of area on the surface of the conductor, over which the surface charge density is integrated,</li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle r}">
<semantics>
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<mstyle displaystyle="false" scriptlevel="0">
<mi>r</mi>
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<annotation encoding="application/x-tex">{\textstyle r}</annotation>
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</math></span><img src="./f2dfb06630b52c9e18fcc0a4688da10774206729.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.049ex; height:1.676ex;" alt="{\textstyle r}" loading="lazy"></span> is the length from <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle dS}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
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<mi>d</mi>
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<annotation encoding="application/x-tex">{\textstyle dS}</annotation>
</semantics>
</math></span><img src="./a4d5150354609d35245fc96ee526f91f45d66838.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.715ex; height:2.176ex;" alt="{\textstyle dS}" loading="lazy"></span> to a fixed point <i>M</i> on the conductor,</li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \varepsilon _{0}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>ε<!-- ε --></mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>0</mn>
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<annotation encoding="application/x-tex">{\displaystyle \varepsilon _{0}}</annotation>
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</math></span><img src="./acb0a8377db20e42274444cb181d51b5532b5844.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.138ex; height:2.009ex;" alt="{\displaystyle \varepsilon _{0}}" loading="lazy"></span> is the <a href="Vacuum_permittivity" title="Vacuum permittivity">vacuum permittivity</a>.</li></ul>
<p>Using this method, the self capacitance of a conducting sphere of radius <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle R}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>R</mi>
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<annotation encoding="application/x-tex">{\textstyle R}</annotation>
</semantics>
</math></span><img src="./197e66194eb64577670e2a100026bff6fb15d236.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.764ex; height:2.176ex;" alt="{\textstyle R}" loading="lazy"></span> in free space (i.e. far away from any other charge distributions) is:<sup id="cite_ref-NSW_2-1" class="reference"><a href="#cite_note-NSW-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C=4\pi \varepsilon _{0}R.}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>C</mi>
<mo>=</mo>
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<msub>
<mi>ε<!-- ε --></mi>
<mrow class="MJX-TeXAtom-ORD">
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</msub>
<mi>R</mi>
<mo>.</mo>
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<annotation encoding="application/x-tex">{\displaystyle C=4\pi \varepsilon _{0}R.}</annotation>
</semantics>
</math></span></span>
</p><p>Example values of self capacitance are:
</p>
<ul><li>for the top "plate" of a <a href="Van_de_Graaff_generator" title="Van de Graaff generator">van de Graaff generator</a>, typically a sphere 20 cm in radius: 22.24 pF,</li>
<li>the planet <a href="Earth" title="Earth">Earth</a>: about 710 μF.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup></li></ul>
<p>The inter-winding capacitance of a <a href="Electromagnetic_coil" title="Electromagnetic coil">coil</a> is sometimes called self capacitance,<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> but this is a different phenomenon. It is actually mutual capacitance between the individual turns of the coil and is a form of stray or <a href="Parasitic_capacitance" title="Parasitic capacitance">parasitic capacitance</a>. This self capacitance is an important consideration at high frequencies: it changes the <a href="Electrical_impedance" title="Electrical impedance">impedance</a> of the coil and gives rise to parallel <a href="Electrical_resonance" title="Electrical resonance">resonance</a>. In many applications this is an undesirable effect and sets an upper frequency limit for the correct operation of the circuit.
</p>
<div class="mw-heading mw-heading2"><h2 id="Mutual_capacitance">Mutual capacitance</h2></div>
<p>A common form is a parallel-plate <a href="Capacitor" title="Capacitor">capacitor</a>, which consists of two conductive plates insulated from each other, usually sandwiching a <a href="Dielectric" title="Dielectric">dielectric</a> material. In a parallel plate capacitor, capacitance is very nearly proportional to the surface area of the conductor plates and inversely proportional to the separation distance between the plates.
</p><p>If the charges on the plates are <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle +q}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mo>+</mo>
<mi>q</mi>
</mstyle>
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<annotation encoding="application/x-tex">{\textstyle +q}</annotation>
</semantics>
</math></span><img src="./e01b6be93d1af857b742f24acc35a9d1e975e7cd.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.878ex; height:2.343ex;" alt="{\textstyle +q}" loading="lazy"></span> and <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle -q}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
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<mo>−<!-- − --></mo>
<mi>q</mi>
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<annotation encoding="application/x-tex">{\textstyle -q}</annotation>
</semantics>
</math></span><img src="./fdd664c9a379cb62fe3d5e3927e79f7651c8851c.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.878ex; height:2.343ex;" alt="{\textstyle -q}" loading="lazy"></span>, and <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle V}">
<semantics>
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<annotation encoding="application/x-tex">{\textstyle V}</annotation>
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</math></span><img src="./d67b50b7ba03a56fea637093cf80e12807852d19.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.787ex; height:2.176ex;" alt="{\textstyle V}" loading="lazy"></span> gives the <a href="Voltage" title="Voltage">voltage</a> between the plates, then the capacitance <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle C}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
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<annotation encoding="application/x-tex">{\textstyle C}</annotation>
</semantics>
</math></span><img src="./6dca76d9ff4b48256b6a4a99bcb234b64b2fa72b.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.766ex; height:2.176ex;" alt="{\textstyle C}" loading="lazy"></span> is given by <span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C={\frac {q}{V}},}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>C</mi>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mi>q</mi>
<mi>V</mi>
</mfrac>
</mrow>
<mo>,</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle C={\frac {q}{V}},}</annotation>
</semantics>
</math></span></span>
which gives the voltage/<a href="Electric_current" title="Electric current">current</a> relationship
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle i(t)=C{\frac {dv(t)}{dt}}+V{\frac {dC}{dt}},}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>i</mi>
<mo stretchy="false">(</mo>
<mi>t</mi>
<mo stretchy="false">)</mo>
<mo>=</mo>
<mi>C</mi>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi>d</mi>
<mi>v</mi>
<mo stretchy="false">(</mo>
<mi>t</mi>
<mo stretchy="false">)</mo>
</mrow>
<mrow>
<mi>d</mi>
<mi>t</mi>
</mrow>
</mfrac>
</mrow>
<mo>+</mo>
<mi>V</mi>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi>d</mi>
<mi>C</mi>
</mrow>
<mrow>
<mi>d</mi>
<mi>t</mi>
</mrow>
</mfrac>
</mrow>
<mo>,</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle i(t)=C{\frac {dv(t)}{dt}}+V{\frac {dC}{dt}},}</annotation>
</semantics>
</math></span></span>
where <big><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle {\frac {dv(t)}{dt}}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi>d</mi>
<mi>v</mi>
<mo stretchy="false">(</mo>
<mi>t</mi>
<mo stretchy="false">)</mo>
</mrow>
<mrow>
<mi>d</mi>
<mi>t</mi>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle {\frac {dv(t)}{dt}}}</annotation>
</semantics>
</math></span><img src="./1296c62ad33ac50df8569d468b43c941416cf458.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.338ex; width:4.366ex; height:4.343ex;" alt="{\textstyle {\frac {dv(t)}{dt}}}" loading="lazy"></span></big> is the instantaneous rate of change of voltage, and <big><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle {\frac {dC}{dt}}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi>d</mi>
<mi>C</mi>
</mrow>
<mrow>
<mi>d</mi>
<mi>t</mi>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle {\frac {dC}{dt}}}</annotation>
</semantics>
</math></span><img src="./4cea8d9be913286386806ebdc1f9c4934dc7ed7f.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.338ex; width:2.945ex; height:3.843ex;" alt="{\textstyle {\frac {dC}{dt}}}" loading="lazy"></span></big> is the instantaneous rate of change of the capacitance. For most applications, the change in capacitance over time is negligible, so the formula reduces to:
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle i(t)=C{\frac {dv(t)}{dt}},}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>i</mi>
<mo stretchy="false">(</mo>
<mi>t</mi>
<mo stretchy="false">)</mo>
<mo>=</mo>
<mi>C</mi>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi>d</mi>
<mi>v</mi>
<mo stretchy="false">(</mo>
<mi>t</mi>
<mo stretchy="false">)</mo>
</mrow>
<mrow>
<mi>d</mi>
<mi>t</mi>
</mrow>
</mfrac>
</mrow>
<mo>,</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle i(t)=C{\frac {dv(t)}{dt}},}</annotation>
</semantics>
</math></span></span>
</p><p>The energy stored in a capacitor is found by <a href="Integral" title="Integral">integrating</a> the work <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle W}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>W</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle W}</annotation>
</semantics>
</math></span><img src="./e95737ee2530885a10b104e9cd5331077e1c88d5.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.435ex; height:2.176ex;" alt="{\textstyle W}" loading="lazy"></span>:
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle W_{\text{charging}}={\frac {1}{2}}CV^{2}.}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>W</mi>
<mrow class="MJX-TeXAtom-ORD">
<mtext>charging</mtext>
</mrow>
</msub>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>1</mn>
<mn>2</mn>
</mfrac>
</mrow>
<mi>C</mi>
<msup>
<mi>V</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mo>.</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle W_{\text{charging}}={\frac {1}{2}}CV^{2}.}</annotation>
</semantics>
</math></span></span>
</p>
<div class="mw-heading mw-heading3"><h3 id="Capacitance_matrix">Capacitance matrix</h3></div>
<p>The discussion above is limited to the case of two conducting plates, although of arbitrary size and shape. The definition <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C=Q/V}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>C</mi>
<mo>=</mo>
<mi>Q</mi>
<mrow class="MJX-TeXAtom-ORD">
<mo>/</mo>
</mrow>
<mi>V</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle C=Q/V}</annotation>
</semantics>
</math></span><img src="./865af670ac05c87761922dc6685480d11f616622.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:9.653ex; height:2.843ex;" alt="{\displaystyle C=Q/V}" loading="lazy"></span> does not apply when there are more than two charged plates, or when the net charge on the two plates is non-zero. To handle this case, <a href="James_Clerk_Maxwell" title="James Clerk Maxwell">James Clerk Maxwell</a> introduced his <i><a href="Coefficients_of_potential" title="Coefficients of potential">coefficients of potential</a></i>. If three (nearly ideal) conductors are given charges <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle Q_{1},Q_{2},Q_{3}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>Q</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
</msub>
<mo>,</mo>
<msub>
<mi>Q</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msub>
<mo>,</mo>
<msub>
<mi>Q</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>3</mn>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle Q_{1},Q_{2},Q_{3}}</annotation>
</semantics>
</math></span><img src="./9ddf0d0c3a5913a13ec2b1f92a68ac2f0e035a7f.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:10.746ex; height:2.509ex;" alt="{\displaystyle Q_{1},Q_{2},Q_{3}}" loading="lazy"></span>, then the voltage at conductor 1 is given by
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle V_{1}=P_{11}Q_{1}+P_{12}Q_{2}+P_{13}Q_{3},}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>V</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
</msub>
<mo>=</mo>
<msub>
<mi>P</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>11</mn>
</mrow>
</msub>
<msub>
<mi>Q</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
</msub>
<mo>+</mo>
<msub>
<mi>P</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>12</mn>
</mrow>
</msub>
<msub>
<mi>Q</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msub>
<mo>+</mo>
<msub>
<mi>P</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>13</mn>
</mrow>
</msub>
<msub>
<mi>Q</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>3</mn>
</mrow>
</msub>
<mo>,</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle V_{1}=P_{11}Q_{1}+P_{12}Q_{2}+P_{13}Q_{3},}</annotation>
</semantics>
</math></span></span>
and similarly for the other voltages. <a href="Hermann_von_Helmholtz" title="Hermann von Helmholtz">Hermann von Helmholtz</a> and <a href="Sir_William_Thomson" class="mw-redirect" title="Sir William Thomson">Sir William Thomson</a> showed that the coefficients of potential are symmetric, so that <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle P_{12}=P_{21}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>P</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>12</mn>
</mrow>
</msub>
<mo>=</mo>
<msub>
<mi>P</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>21</mn>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle P_{12}=P_{21}}</annotation>
</semantics>
</math></span><img src="./9fa70d2158b9f7cc1e64b1f4a56a15d84d257b4a.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:9.835ex; height:2.509ex;" alt="{\displaystyle P_{12}=P_{21}}" loading="lazy"></span>, etc. Thus the system can be described by a collection of coefficients known as the <i>elastance matrix</i> or <i>reciprocal capacitance matrix</i>, which is defined as:
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle P_{ij}={\frac {\partial V_{i}}{\partial Q_{j}}}.}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>P</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>i</mi>
<mi>j</mi>
</mrow>
</msub>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi mathvariant="normal">∂<!-- ∂ --></mi>
<msub>
<mi>V</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>i</mi>
</mrow>
</msub>
</mrow>
<mrow>
<mi mathvariant="normal">∂<!-- ∂ --></mi>
<msub>
<mi>Q</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>j</mi>
</mrow>
</msub>
</mrow>
</mfrac>
</mrow>
<mo>.</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle P_{ij}={\frac {\partial V_{i}}{\partial Q_{j}}}.}</annotation>
</semantics>
</math></span></span>
</p><p>From this, the mutual capacitance <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C_{m}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>C</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>m</mi>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle C_{m}}</annotation>
</semantics>
</math></span><img src="./957e2166e45b11d83b27710666eb7aa38f5e4b89.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:3.337ex; height:2.509ex;" alt="{\displaystyle C_{m}}" loading="lazy"></span> between two objects can be defined<sup id="cite_ref-Jackson1999_7-0" class="reference"><a href="#cite_note-Jackson1999-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> by solving for the total charge <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle Q}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>Q</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle Q}</annotation>
</semantics>
</math></span><img src="./131bb2da649dd6c113517c5ae8c26370654ee8fa.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:1.838ex; height:2.509ex;" alt="{\textstyle Q}" loading="lazy"></span> and using <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C_{m}=Q/V}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>C</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>m</mi>
</mrow>
</msub>
<mo>=</mo>
<mi>Q</mi>
<mrow class="MJX-TeXAtom-ORD">
<mo>/</mo>
</mrow>
<mi>V</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle C_{m}=Q/V}</annotation>
</semantics>
</math></span><img src="./d24afcadedbbc56d62143a03b465e321d6a43f7b.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:11.223ex; height:2.843ex;" alt="{\displaystyle C_{m}=Q/V}" loading="lazy"></span>.
</p><p><span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C_{m}={\frac {1}{(P_{11}+P_{22})-(P_{12}+P_{21})}}.}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>C</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>m</mi>
</mrow>
</msub>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>1</mn>
<mrow>
<mo stretchy="false">(</mo>
<msub>
<mi>P</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>11</mn>
</mrow>
</msub>
<mo>+</mo>
<msub>
<mi>P</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>22</mn>
</mrow>
</msub>
<mo stretchy="false">)</mo>
<mo>−<!-- − --></mo>
<mo stretchy="false">(</mo>
<msub>
<mi>P</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>12</mn>
</mrow>
</msub>
<mo>+</mo>
<msub>
<mi>P</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>21</mn>
</mrow>
</msub>
<mo stretchy="false">)</mo>
</mrow>
</mfrac>
</mrow>
<mo>.</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle C_{m}={\frac {1}{(P_{11}+P_{22})-(P_{12}+P_{21})}}.}</annotation>
</semantics>
</math></span></span>
</p><p>Since no actual device holds perfectly equal and opposite charges on each of the two "plates", it is the mutual capacitance that is reported on capacitors.
</p><p>The collection of coefficients <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C_{ij}={\frac {\partial Q_{i}}{\partial V_{j}}}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>C</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>i</mi>
<mi>j</mi>
</mrow>
</msub>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi mathvariant="normal">∂<!-- ∂ --></mi>
<msub>
<mi>Q</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>i</mi>
</mrow>
</msub>
</mrow>
<mrow>
<mi mathvariant="normal">∂<!-- ∂ --></mi>
<msub>
<mi>V</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>j</mi>
</mrow>
</msub>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle C_{ij}={\frac {\partial Q_{i}}{\partial V_{j}}}}</annotation>
</semantics>
</math></span><img src="./5531170cf5666234fc34baadfa12b176321997e9.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.671ex; width:11.03ex; height:6.176ex;" alt="{\displaystyle C_{ij}={\frac {\partial Q_{i}}{\partial V_{j}}}}" loading="lazy"></span> is known as the <i>capacitance matrix</i>,<sup id="cite_ref-maxwell_8-0" class="reference"><a href="#cite_note-maxwell-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> and is the <a href="Matrix_inverse" class="mw-redirect" title="Matrix inverse">inverse</a> of the elastance matrix.
</p>
<div class="mw-heading mw-heading2"><h2 id="Capacitors">Capacitors</h2></div>
<div role="note" class="hatnote navigation-not-searchable">Main article: <a href="Capacitor" title="Capacitor">Capacitor</a></div>
<p>The capacitance of the majority of capacitors used in electronic circuits is generally several orders of magnitude smaller than the <a href="Farad" title="Farad">farad</a>. The most common units of capacitance are the <a href="Micro-" title="Micro-">microfarad</a> (μF), <a href="Nano-" title="Nano-">nanofarad</a> (nF), <a href="Pico-" class="mw-redirect" title="Pico-">picofarad</a> (pF), and, in microcircuits, <a href="Femto-" class="mw-redirect" title="Femto-">femtofarad</a> (fF). Some applications also use <a href="Supercapacitors" class="mw-redirect" title="Supercapacitors">supercapacitors</a> that can be much larger, as much as hundreds of farads, and parasitic capacitive elements can be less than a femtofarad. Historical texts use other, obsolete submultiples of the farad, such as "mf" and "mfd" for microfarad (μF); "mmf", "mmfd", "pfd", "μμF" for picofarad (pF).<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup>
</p><p>The capacitance can be calculated if the geometry of the conductors and the dielectric properties of the insulator between the conductors are known. Capacitance is proportional to the area of overlap and inversely proportional to the separation between conducting sheets. The closer the sheets are to each other, the greater the capacitance.
</p><p>An example is the capacitance of a capacitor constructed of two parallel plates both of area <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle A}">
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<annotation encoding="application/x-tex">{\textstyle A}</annotation>
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</math></span><img src="./a118c6ad00742b3f5dccd2f0e74b5e369df6fd31.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\textstyle A}" loading="lazy"></span> separated by a distance <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle d}">
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<annotation encoding="application/x-tex">{\textstyle d}</annotation>
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</math></span><img src="./252135f29da0e9f9e130ff2d53be5df2f7044d99.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.216ex; height:2.176ex;" alt="{\textstyle d}" loading="lazy"></span>. If <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle d}">
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<annotation encoding="application/x-tex">{\textstyle d}</annotation>
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</math></span><img src="./252135f29da0e9f9e130ff2d53be5df2f7044d99.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.216ex; height:2.176ex;" alt="{\textstyle d}" loading="lazy"></span> is sufficiently small with respect to the smallest chord of <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle A}">
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</math></span><img src="./a118c6ad00742b3f5dccd2f0e74b5e369df6fd31.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\textstyle A}" loading="lazy"></span>, there holds, to a high level of accuracy:
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \ C=\varepsilon {\frac {A}{d}};}">
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<annotation encoding="application/x-tex">{\displaystyle \ C=\varepsilon {\frac {A}{d}};}</annotation>
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</p><p><span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \varepsilon =\varepsilon _{0}\varepsilon _{r},}">
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<annotation encoding="application/x-tex">{\displaystyle \varepsilon =\varepsilon _{0}\varepsilon _{r},}</annotation>
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</p><p>where
</p>
<ul><li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle C}">
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<mi>C</mi>
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<annotation encoding="application/x-tex">{\textstyle C}</annotation>
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</math></span><img src="./6dca76d9ff4b48256b6a4a99bcb234b64b2fa72b.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.766ex; height:2.176ex;" alt="{\textstyle C}" loading="lazy"></span> is the capacitance, in farads;</li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle A}">
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<mi>A</mi>
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</math></span><img src="./a118c6ad00742b3f5dccd2f0e74b5e369df6fd31.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\textstyle A}" loading="lazy"></span> is the area of overlap of the two plates, in square meters;</li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle \varepsilon _{0}}">
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<annotation encoding="application/x-tex">{\textstyle \varepsilon _{0}}</annotation>
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</math></span><img src="./1b8b05479dc2dccbc42ee2f8d1b45d99a49b0a61.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.138ex; height:2.009ex;" alt="{\textstyle \varepsilon _{0}}" loading="lazy"></span> is the <a href="Vacuum_permittivity" title="Vacuum permittivity">electric constant</a> <span class="nowrap">(<span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle \varepsilon _{0}\approx 8.854\times 10^{-12}~\mathrm {F{\cdot }m^{-1}} }">
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<mi mathvariant="normal">F</mi>
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<annotation encoding="application/x-tex">{\textstyle \varepsilon _{0}\approx 8.854\times 10^{-12}~\mathrm {F{\cdot }m^{-1}} }</annotation>
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</math></span><img src="./1476af647eaf4a8f4365e1240cfe0332840b1762.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:25.867ex; height:3.009ex;" alt="{\textstyle \varepsilon _{0}\approx 8.854\times 10^{-12}~\mathrm {F{\cdot }m^{-1}} }" loading="lazy"></span>);</span></li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle \varepsilon _{r}}">
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<annotation encoding="application/x-tex">{\textstyle \varepsilon _{r}}</annotation>
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</math></span><img src="./6aeb9464ac233fab92afdb47a3cd78da84aef5e3.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.057ex; height:2.009ex;" alt="{\textstyle \varepsilon _{r}}" loading="lazy"></span> is the <a href="Relative_permittivity" title="Relative permittivity">relative permittivity</a> (also dielectric constant) of the material in between the plates <span class="nowrap">(<span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle \varepsilon _{r}\approx 1}">
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<annotation encoding="application/x-tex">{\textstyle \varepsilon _{r}\approx 1}</annotation>
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</math></span><img src="./1ee1c1044ffe74ee870df838a5f2a5ed2e77e622.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:6.318ex; height:2.509ex;" alt="{\textstyle \varepsilon _{r}\approx 1}" loading="lazy"></span></span> for air); and</li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle d}">
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<annotation encoding="application/x-tex">{\textstyle d}</annotation>
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</math></span><img src="./252135f29da0e9f9e130ff2d53be5df2f7044d99.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.216ex; height:2.176ex;" alt="{\textstyle d}" loading="lazy"></span> is the separation between the plates, in meters.</li></ul>
<p>The equation is a good approximation if <i>d</i> is small compared to the other dimensions of the plates so that the <a href="Electric_field" title="Electric field">electric field</a> in the capacitor area is uniform, and the so-called <i>fringing field</i> around the periphery provides only a small contribution to the capacitance.
</p><p>Combining the equation for capacitance with the above equation for the energy stored in a capacitor, for a flat-plate capacitor the energy stored is:
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle W_{\text{stored}}={\frac {1}{2}}CV^{2}={\frac {1}{2}}\varepsilon {\frac {A}{d}}V^{2}.}">
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<annotation encoding="application/x-tex">{\displaystyle W_{\text{stored}}={\frac {1}{2}}CV^{2}={\frac {1}{2}}\varepsilon {\frac {A}{d}}V^{2}.}</annotation>
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where <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle W}">
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</math></span><img src="./e95737ee2530885a10b104e9cd5331077e1c88d5.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.435ex; height:2.176ex;" alt="{\textstyle W}" loading="lazy"></span> is the energy, in joules; <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle C}">
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</math></span><img src="./6dca76d9ff4b48256b6a4a99bcb234b64b2fa72b.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.766ex; height:2.176ex;" alt="{\textstyle C}" loading="lazy"></span> is the capacitance, in farads; and <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle V}">
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</math></span><img src="./d67b50b7ba03a56fea637093cf80e12807852d19.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.787ex; height:2.176ex;" alt="{\textstyle V}" loading="lazy"></span> is the voltage, in volts.
</p>
<div class="mw-heading mw-heading2"><h2 id="Stray_capacitance">Stray capacitance</h2></div>
<div role="note" class="hatnote navigation-not-searchable">Main article: <a href="Parasitic_capacitance" title="Parasitic capacitance">Parasitic capacitance</a></div>
<p>Any two adjacent conductors can function as a capacitor, though the capacitance is small unless the conductors are close together for long distances or over a large area. This (often unwanted) capacitance is called parasitic or stray capacitance. Stray capacitance can allow signals to leak between otherwise isolated circuits (an effect called <a href="Crosstalk_(electronics)" class="mw-redirect" title="Crosstalk (electronics)">crosstalk</a>), and it can be a limiting factor for proper functioning of circuits at <a href="High_frequency" title="High frequency">high frequency</a>.
</p><p>Stray capacitance between the input and output in amplifier circuits can be troublesome because it can form a path for <a href="Feedback#Electronic_engineering" title="Feedback">feedback</a>, which can cause instability and <a href="Parasitic_oscillation" title="Parasitic oscillation">parasitic oscillation</a> in the amplifier. It is often convenient for analytical purposes to replace this capacitance with a combination of one input-to-ground capacitance and one output-to-ground capacitance; the original configuration – including the input-to-output capacitance – is often referred to as a pi-configuration. Miller's theorem can be used to effect this replacement: it states that, if the gain ratio of two nodes is <style data-mw-deduplicate="TemplateStyles:r1214402035">
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</style><span class="sfrac"><span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den"><i>K</i></span></span></span>, then an <a href="Electrical_impedance" title="Electrical impedance">impedance</a> of <i>Z</i> connecting the two nodes can be replaced with a <span class="sfrac"><span class="tion"><span class="num"><i>Z</i></span><span class="sr-only">/</span><span class="den">1 − <i>K</i></span></span></span> impedance between the first node and ground and a <span class="sfrac"><span class="tion"><span class="num"><i>KZ</i></span><span class="sr-only">/</span><span class="den"><i>K</i> − 1</span></span></span> impedance between the second node and ground. Since impedance varies inversely with capacitance, the internode capacitance, <i>C</i>, is replaced by a capacitance of KC from input to ground and a capacitance of <span class="sfrac"><span class="tion"><span class="num">(<i>K</i> − 1)<i>C</i></span><span class="sr-only">/</span><span class="den"><i>K</i></span></span></span> from output to ground. When the input-to-output gain is very large, the equivalent input-to-ground impedance is very small while the output-to-ground impedance is essentially equal to the original (input-to-output) impedance.
</p>
<div class="mw-heading mw-heading2"><h2 id="Capacitance_of_conductors_with_simple_shapes">Capacitance of conductors with simple shapes</h2></div>
<p>Calculating the capacitance of a system amounts to solving the <a href="Laplace_equation" class="mw-redirect" title="Laplace equation">Laplace equation</a> <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle \nabla ^{2}\varphi =0}">
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</math></span><img src="./70bb8555569a6795eafa8e2f3e61e59976165de6.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:8.771ex; height:3.009ex;" alt="{\textstyle \nabla ^{2}\varphi =0}" loading="lazy"></span> with a constant potential <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle \varphi }">
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<annotation encoding="application/x-tex">{\textstyle \varphi }</annotation>
</semantics>
</math></span><img src="./99015519246670af1cb5592e439ad64a27fb4830.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:1.52ex; height:2.176ex;" alt="{\textstyle \varphi }" loading="lazy"></span> on the 2-dimensional surface of the conductors embedded in 3-space. This is simplified by symmetries. There is no solution in terms of elementary functions in more complicated cases.
</p><p>For plane situations, analytic functions may be used to map different geometries to each other. See also <a href="Schwarz%E2%80%93Christoffel_mapping" title="Schwarz–Christoffel mapping">Schwarz–Christoffel mapping</a>.
</p>
<table class="wikitable">
<caption>Capacitance of simple systems
</caption>
<tbody><tr>
<th>Type</th>
<th>Capacitance</th>
<th>Diagram and definitions
</th></tr>
<tr>
<th>Parallel-plate capacitor
</th>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \ {\mathcal {C}}={\frac {\ \varepsilon A\ }{d}}\ }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mtext> </mtext>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mi class="MJX-tex-caligraphic" mathvariant="script">C</mi>
</mrow>
</mrow>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mtext> </mtext>
<mi>ε<!-- ε --></mi>
<mi>A</mi>
<mtext> </mtext>
</mrow>
<mi>d</mi>
</mfrac>
</mrow>
<mtext> </mtext>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \ {\mathcal {C}}={\frac {\ \varepsilon A\ }{d}}\ }</annotation>
</semantics>
</math></span><img src="./7735e66558544f1da2bcc9f59f04ce6b053e5058.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.005ex; width:10.323ex; height:5.509ex;" alt="{\displaystyle \ {\mathcal {C}}={\frac {\ \varepsilon A\ }{d}}\ }" loading="lazy"></span>
</td>
<td><span typeof="mw:File"></span>
<ul><li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle \varepsilon }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>ε<!-- ε --></mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle \varepsilon }</annotation>
</semantics>
</math></span><img src="./2193f5fc8a6dd05f24e01d0789b78ec2b57515ba.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.083ex; height:1.676ex;" alt="{\textstyle \varepsilon }" loading="lazy"></span>: <a href="Permittivity" title="Permittivity">Permittivity</a></li></ul>
</td></tr>
<tr>
<th>Concentric cylinders
</th>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \ {\mathcal {C}}={\frac {2\pi \varepsilon \ell }{\ \ln \left(R_{2}/R_{1}\right)\ }}\ }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mtext> </mtext>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mi class="MJX-tex-caligraphic" mathvariant="script">C</mi>
</mrow>
</mrow>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mn>2</mn>
<mi>π<!-- π --></mi>
<mi>ε<!-- ε --></mi>
<mi>ℓ<!-- ℓ --></mi>
</mrow>
<mrow>
<mtext> </mtext>
<mi>ln</mi>
<mo><!-- --></mo>
<mrow>
<mo>(</mo>
<mrow>
<msub>
<mi>R</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msub>
<mrow class="MJX-TeXAtom-ORD">
<mo>/</mo>
</mrow>
<msub>
<mi>R</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
</msub>
</mrow>
<mo>)</mo>
</mrow>
<mtext> </mtext>
</mrow>
</mfrac>
</mrow>
<mtext> </mtext>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \ {\mathcal {C}}={\frac {2\pi \varepsilon \ell }{\ \ln \left(R_{2}/R_{1}\right)\ }}\ }</annotation>
</semantics>
</math></span><img src="./b06b7319a2b03715d547260b5f0983f32f0b6f11.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.671ex; width:18.431ex; height:6.176ex;" alt="{\displaystyle \ {\mathcal {C}}={\frac {2\pi \varepsilon \ell }{\ \ln \left(R_{2}/R_{1}\right)\ }}\ }" loading="lazy"></span>
</td>
<td><span typeof="mw:File"></span>
<ul><li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle \varepsilon }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>ε<!-- ε --></mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle \varepsilon }</annotation>
</semantics>
</math></span><img src="./2193f5fc8a6dd05f24e01d0789b78ec2b57515ba.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.083ex; height:1.676ex;" alt="{\textstyle \varepsilon }" loading="lazy"></span>: <a href="Permittivity" title="Permittivity">Permittivity</a></li></ul>
</td></tr>
<tr>
<th>Eccentric cylinders<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup>
</th>
<td><big><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \ {\mathcal {C}}={\frac {2\pi \varepsilon \ell }{\ \operatorname {arcosh} \left({\frac {R_{1}^{2}+R_{2}^{2}-d^{2}}{2R_{1}R_{2}}}\right)\ }}\ }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mtext> </mtext>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mi class="MJX-tex-caligraphic" mathvariant="script">C</mi>
</mrow>
</mrow>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mn>2</mn>
<mi>π<!-- π --></mi>
<mi>ε<!-- ε --></mi>
<mi>ℓ<!-- ℓ --></mi>
</mrow>
<mrow>
<mtext> </mtext>
<mi>arcosh</mi>
<mo><!-- --></mo>
<mrow>
<mo>(</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<msubsup>
<mi>R</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msubsup>
<mo>+</mo>
<msubsup>
<mi>R</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msubsup>
<mo>−<!-- − --></mo>
<msup>
<mi>d</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
</mrow>
<mrow>
<mn>2</mn>
<msub>
<mi>R</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
</msub>
<msub>
<mi>R</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msub>
</mrow>
</mfrac>
</mrow>
<mo>)</mo>
</mrow>
<mtext> </mtext>
</mrow>
</mfrac>
</mrow>
<mtext> </mtext>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \ {\mathcal {C}}={\frac {2\pi \varepsilon \ell }{\ \operatorname {arcosh} \left({\frac {R_{1}^{2}+R_{2}^{2}-d^{2}}{2R_{1}R_{2}}}\right)\ }}\ }</annotation>
</semantics>
</math></span><img src="./d569a9ab5e37276c71038dacfd91e9486ab3e051.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -5.838ex; width:27.026ex; height:9.343ex;" alt="{\displaystyle \ {\mathcal {C}}={\frac {2\pi \varepsilon \ell }{\ \operatorname {arcosh} \left({\frac {R_{1}^{2}+R_{2}^{2}-d^{2}}{2R_{1}R_{2}}}\right)\ }}\ }" loading="lazy"></span></big>
</td>
<td><span typeof="mw:File"></span>
<ul><li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle \varepsilon }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>ε<!-- ε --></mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle \varepsilon }</annotation>
</semantics>
</math></span><img src="./2193f5fc8a6dd05f24e01d0789b78ec2b57515ba.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.083ex; height:1.676ex;" alt="{\textstyle \varepsilon }" loading="lazy"></span>: <a href="Permittivity" title="Permittivity">Permittivity</a></li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle R_{1}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<msub>
<mi>R</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle R_{1}}</annotation>
</semantics>
</math></span><img src="./c115730d178ae9c5ffe2747f97a29c73698f9d4b.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.818ex; height:2.509ex;" alt="{\textstyle R_{1}}" loading="lazy"></span>: Outer radius</li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle R_{2}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<msub>
<mi>R</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle R_{2}}</annotation>
</semantics>
</math></span><img src="./eeb9f9b1a756c21ec0dd01be6df73c2fe1776753.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.818ex; height:2.509ex;" alt="{\textstyle R_{2}}" loading="lazy"></span>: Inner radius</li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle d}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>d</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle d}</annotation>
</semantics>
</math></span><img src="./252135f29da0e9f9e130ff2d53be5df2f7044d99.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.216ex; height:2.176ex;" alt="{\textstyle d}" loading="lazy"></span>: Distance between center</li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle \ell }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>ℓ<!-- ℓ --></mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle \ell }</annotation>
</semantics>
</math></span><img src="./554d626bee80ffdb3ab924a78a2d05c5a9e642db.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:0.97ex; height:2.176ex;" alt="{\textstyle \ell }" loading="lazy"></span>: Wire length</li></ul>
</td></tr>
<tr>
<th>Pair of parallel wires<sup id="cite_ref-Jackson_1975_80_14-0" class="reference"><a href="#cite_note-Jackson_1975_80-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup>
</th>
<td><big><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \ {\mathcal {C}}={\frac {\pi \varepsilon \ell }{\ \operatorname {arcosh} \left({\frac {d}{2a}}\right)\ }}={\frac {\pi \varepsilon \ell }{\ \ln \left({\frac {d}{\ 2a\ }}+{\sqrt {{\frac {d^{2}}{\ 4a^{2}\ }}-1\ }}\right)\ }}\ }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mtext> </mtext>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mi class="MJX-tex-caligraphic" mathvariant="script">C</mi>
</mrow>
</mrow>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi>π<!-- π --></mi>
<mi>ε<!-- ε --></mi>
<mi>ℓ<!-- ℓ --></mi>
</mrow>
<mrow>
<mtext> </mtext>
<mi>arcosh</mi>
<mo><!-- --></mo>
<mrow>
<mo>(</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mi>d</mi>
<mrow>
<mn>2</mn>
<mi>a</mi>
</mrow>
</mfrac>
</mrow>
<mo>)</mo>
</mrow>
<mtext> </mtext>
</mrow>
</mfrac>
</mrow>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi>π<!-- π --></mi>
<mi>ε<!-- ε --></mi>
<mi>ℓ<!-- ℓ --></mi>
</mrow>
<mrow>
<mtext> </mtext>
<mi>ln</mi>
<mo><!-- --></mo>
<mrow>
<mo>(</mo>
<mrow>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mi>d</mi>
<mrow>
<mtext> </mtext>
<mn>2</mn>
<mi>a</mi>
<mtext> </mtext>
</mrow>
</mfrac>
</mrow>
<mo>+</mo>
<mrow class="MJX-TeXAtom-ORD">
<msqrt>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<msup>
<mi>d</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mrow>
<mtext> </mtext>
<mn>4</mn>
<msup>
<mi>a</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mtext> </mtext>
</mrow>
</mfrac>
</mrow>
<mo>−<!-- − --></mo>
<mn>1</mn>
<mtext> </mtext>
</msqrt>
</mrow>
</mrow>
<mo>)</mo>
</mrow>
<mtext> </mtext>
</mrow>
</mfrac>
</mrow>
<mtext> </mtext>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \ {\mathcal {C}}={\frac {\pi \varepsilon \ell }{\ \operatorname {arcosh} \left({\frac {d}{2a}}\right)\ }}={\frac {\pi \varepsilon \ell }{\ \ln \left({\frac {d}{\ 2a\ }}+{\sqrt {{\frac {d^{2}}{\ 4a^{2}\ }}-1\ }}\right)\ }}\ }</annotation>
</semantics>
</math></span><img src="./d2d59c44af29370e08de9cd6d0c90bdbb50973fc.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -6.171ex; width:48.465ex; height:9.676ex;" alt="{\displaystyle \ {\mathcal {C}}={\frac {\pi \varepsilon \ell }{\ \operatorname {arcosh} \left({\frac {d}{2a}}\right)\ }}={\frac {\pi \varepsilon \ell }{\ \ln \left({\frac {d}{\ 2a\ }}+{\sqrt {{\frac {d^{2}}{\ 4a^{2}\ }}-1\ }}\right)\ }}\ }" loading="lazy"></span></big>
</td>
<td><span typeof="mw:File"></span>
</td></tr>
<tr>
<th>Wire parallel to wall<sup id="cite_ref-Jackson_1975_80_14-1" class="reference"><a href="#cite_note-Jackson_1975_80-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup>
</th>
<td><big><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \ {\mathcal {C}}={\frac {2\pi \varepsilon \ell }{\ \operatorname {arcosh} \left({\frac {d}{a}}\right)\ }}={\frac {2\pi \varepsilon \ell }{\ \ln \left({\frac {\ d\ }{a}}+{\sqrt {{\frac {\ d^{2}\ }{a^{2}}}-1\ }}\right)\ }}\ }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mtext> </mtext>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mi class="MJX-tex-caligraphic" mathvariant="script">C</mi>
</mrow>
</mrow>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mn>2</mn>
<mi>π<!-- π --></mi>
<mi>ε<!-- ε --></mi>
<mi>ℓ<!-- ℓ --></mi>
</mrow>
<mrow>
<mtext> </mtext>
<mi>arcosh</mi>
<mo><!-- --></mo>
<mrow>
<mo>(</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mi>d</mi>
<mi>a</mi>
</mfrac>
</mrow>
<mo>)</mo>
</mrow>
<mtext> </mtext>
</mrow>
</mfrac>
</mrow>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mn>2</mn>
<mi>π<!-- π --></mi>
<mi>ε<!-- ε --></mi>
<mi>ℓ<!-- ℓ --></mi>
</mrow>
<mrow>
<mtext> </mtext>
<mi>ln</mi>
<mo><!-- --></mo>
<mrow>
<mo>(</mo>
<mrow>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mtext> </mtext>
<mi>d</mi>
<mtext> </mtext>
</mrow>
<mi>a</mi>
</mfrac>
</mrow>
<mo>+</mo>
<mrow class="MJX-TeXAtom-ORD">
<msqrt>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mtext> </mtext>
<msup>
<mi>d</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mtext> </mtext>
</mrow>
<msup>
<mi>a</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
</mfrac>
</mrow>
<mo>−<!-- − --></mo>
<mn>1</mn>
<mtext> </mtext>
</msqrt>
</mrow>
</mrow>
<mo>)</mo>
</mrow>
<mtext> </mtext>
</mrow>
</mfrac>
</mrow>
<mtext> </mtext>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \ {\mathcal {C}}={\frac {2\pi \varepsilon \ell }{\ \operatorname {arcosh} \left({\frac {d}{a}}\right)\ }}={\frac {2\pi \varepsilon \ell }{\ \ln \left({\frac {\ d\ }{a}}+{\sqrt {{\frac {\ d^{2}\ }{a^{2}}}-1\ }}\right)\ }}\ }</annotation>
</semantics>
</math></span><img src="./6dfa22478b0ba56a15df895367f2cdab038f3aa2.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -6.171ex; width:45.981ex; height:9.676ex;" alt="{\displaystyle \ {\mathcal {C}}={\frac {2\pi \varepsilon \ell }{\ \operatorname {arcosh} \left({\frac {d}{a}}\right)\ }}={\frac {2\pi \varepsilon \ell }{\ \ln \left({\frac {\ d\ }{a}}+{\sqrt {{\frac {\ d^{2}\ }{a^{2}}}-1\ }}\right)\ }}\ }" loading="lazy"></span></big>
</td>
<td>
<ul><li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle a}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>a</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle a}</annotation>
</semantics>
</math></span><img src="./7a503f107a7c104e40e484cee9e1f5993d28ffd8.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.23ex; height:1.676ex;" alt="{\textstyle a}" loading="lazy"></span>: Wire radius</li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle d}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>d</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle d}</annotation>
</semantics>
</math></span><img src="./252135f29da0e9f9e130ff2d53be5df2f7044d99.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.216ex; height:2.176ex;" alt="{\textstyle d}" loading="lazy"></span>: Distance, <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle d>a}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>d</mi>
<mo>></mo>
<mi>a</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle d>a}</annotation>
</semantics>
</math></span><img src="./2f0cadff95880044e8c805b6e1a9410d5057ea53.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:5.544ex; height:2.176ex;" alt="{\textstyle d>a}" loading="lazy"></span></li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle \ell }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>ℓ<!-- ℓ --></mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle \ell }</annotation>
</semantics>
</math></span><img src="./554d626bee80ffdb3ab924a78a2d05c5a9e642db.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:0.97ex; height:2.176ex;" alt="{\textstyle \ell }" loading="lazy"></span>: Wire length</li></ul>
</td></tr>
<tr>
<th>Two parallel<br>coplanar strips<sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup>
</th>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \ {\mathcal {C}}=\varepsilon \ell \ {\frac {\ K\left({\sqrt {1-k^{2}\ }}\right)\ }{2K\left(k\right)}}\ }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mtext> </mtext>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mi class="MJX-tex-caligraphic" mathvariant="script">C</mi>
</mrow>
</mrow>
<mo>=</mo>
<mi>ε<!-- ε --></mi>
<mi>ℓ<!-- ℓ --></mi>
<mtext> </mtext>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mtext> </mtext>
<mi>K</mi>
<mrow>
<mo>(</mo>
<mrow class="MJX-TeXAtom-ORD">
<msqrt>
<mn>1</mn>
<mo>−<!-- − --></mo>
<msup>
<mi>k</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mtext> </mtext>
</msqrt>
</mrow>
<mo>)</mo>
</mrow>
<mtext> </mtext>
</mrow>
<mrow>
<mn>2</mn>
<mi>K</mi>
<mrow>
<mo>(</mo>
<mi>k</mi>
<mo>)</mo>
</mrow>
</mrow>
</mfrac>
</mrow>
<mtext> </mtext>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \ {\mathcal {C}}=\varepsilon \ell \ {\frac {\ K\left({\sqrt {1-k^{2}\ }}\right)\ }{2K\left(k\right)}}\ }</annotation>
</semantics>
</math></span><img src="./afdfbdf222551282a32f3596c49ca6c4311f8222.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.671ex; width:24.918ex; height:8.343ex;" alt="{\displaystyle \ {\mathcal {C}}=\varepsilon \ell \ {\frac {\ K\left({\sqrt {1-k^{2}\ }}\right)\ }{2K\left(k\right)}}\ }" loading="lazy"></span>
</td>
<td>
<ul><li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle d}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>d</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle d}</annotation>
</semantics>
</math></span><img src="./252135f29da0e9f9e130ff2d53be5df2f7044d99.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.216ex; height:2.176ex;" alt="{\textstyle d}" loading="lazy"></span>: Distance</li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle \ell }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>ℓ<!-- ℓ --></mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle \ell }</annotation>
</semantics>
</math></span><img src="./554d626bee80ffdb3ab924a78a2d05c5a9e642db.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:0.97ex; height:2.176ex;" alt="{\textstyle \ell }" loading="lazy"></span>: Length</li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle w_{1},w_{2}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<msub>
<mi>w</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
</msub>
<mo>,</mo>
<msub>
<mi>w</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle w_{1},w_{2}}</annotation>
</semantics>
</math></span><img src="./04e1e5ec5dd45d8357be9a5ad9a8d336df9e6bdb.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:6.471ex; height:2.009ex;" alt="{\textstyle w_{1},w_{2}}" loading="lazy"></span>: Strip width</li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle \ k_{1}=\left({\tfrac {\ 2w_{1}\ }{d}}+1\right)^{-1}\ }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mtext> </mtext>
<msub>
<mi>k</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
</msub>
<mo>=</mo>
<msup>
<mrow>
<mo>(</mo>
<mrow>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mfrac>
<mrow>
<mtext> </mtext>
<mn>2</mn>
<msub>
<mi>w</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
</msub>
<mtext> </mtext>
</mrow>
<mi>d</mi>
</mfrac>
</mstyle>
</mrow>
<mo>+</mo>
<mn>1</mn>
</mrow>
<mo>)</mo>
</mrow>
<mrow class="MJX-TeXAtom-ORD">
<mo>−<!-- − --></mo>
<mn>1</mn>
</mrow>
</msup>
<mtext> </mtext>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle \ k_{1}=\left({\tfrac {\ 2w_{1}\ }{d}}+1\right)^{-1}\ }</annotation>
</semantics>
</math></span><img src="./2f17a636489192f61f85471d60083f28e08388b8.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:20.464ex; height:5.176ex;" alt="{\textstyle \ k_{1}=\left({\tfrac {\ 2w_{1}\ }{d}}+1\right)^{-1}\ }" loading="lazy"></span><br><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \ k_{2}=\left({\tfrac {\ 2w_{2}\ }{d}}+1\right)^{-1}\ }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mtext> </mtext>
<msub>
<mi>k</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msub>
<mo>=</mo>
<msup>
<mrow>
<mo>(</mo>
<mrow>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mfrac>
<mrow>
<mtext> </mtext>
<mn>2</mn>
<msub>
<mi>w</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msub>
<mtext> </mtext>
</mrow>
<mi>d</mi>
</mfrac>
</mstyle>
</mrow>
<mo>+</mo>
<mn>1</mn>
</mrow>
<mo>)</mo>
</mrow>
<mrow class="MJX-TeXAtom-ORD">
<mo>−<!-- − --></mo>
<mn>1</mn>
</mrow>
</msup>
<mtext> </mtext>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \ k_{2}=\left({\tfrac {\ 2w_{2}\ }{d}}+1\right)^{-1}\ }</annotation>
</semantics>
</math></span><img src="./20d72d42a4f60b759ff3c1f444643c63ed898226.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:20.464ex; height:5.176ex;" alt="{\displaystyle \ k_{2}=\left({\tfrac {\ 2w_{2}\ }{d}}+1\right)^{-1}\ }" loading="lazy"></span><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \ k={\sqrt {k_{1}\ k_{2}\ }}\ }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mtext> </mtext>
<mi>k</mi>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<msqrt>
<msub>
<mi>k</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
</msub>
<mtext> </mtext>
<msub>
<mi>k</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msub>
<mtext> </mtext>
</msqrt>
</mrow>
<mtext> </mtext>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \ k={\sqrt {k_{1}\ k_{2}\ }}\ }</annotation>
</semantics>
</math></span><img src="./8bc82f8cc7cc9e6062c8967f136bd49d7cf649f3.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:13.487ex; height:3.343ex;" alt="{\displaystyle \ k={\sqrt {k_{1}\ k_{2}\ }}\ }" loading="lazy"></span></li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle K}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>K</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle K}</annotation>
</semantics>
</math></span><img src="./985dcc2532a2d4d91b9a9610139216c63cf832d0.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.066ex; height:2.176ex;" alt="{\textstyle K}" loading="lazy"></span>: <a href="Elliptic_integral#Complete_elliptic_integral_of_the_first_kind" title="Elliptic integral">Complete elliptic integral of the first kind</a></li></ul>
</td></tr>
<tr>
<th>Concentric spheres
</th>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \ {\mathcal {C}}={\frac {4\pi \varepsilon }{\ {\frac {1}{R_{1}}}-{\frac {1}{R_{2}}}\ }}\ }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mtext> </mtext>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mi class="MJX-tex-caligraphic" mathvariant="script">C</mi>
</mrow>
</mrow>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mn>4</mn>
<mi>π<!-- π --></mi>
<mi>ε<!-- ε --></mi>
</mrow>
<mrow>
<mtext> </mtext>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>1</mn>
<msub>
<mi>R</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
</msub>
</mfrac>
</mrow>
<mo>−<!-- − --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>1</mn>
<msub>
<mi>R</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msub>
</mfrac>
</mrow>
<mtext> </mtext>
</mrow>
</mfrac>
</mrow>
<mtext> </mtext>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \ {\mathcal {C}}={\frac {4\pi \varepsilon }{\ {\frac {1}{R_{1}}}-{\frac {1}{R_{2}}}\ }}\ }</annotation>
</semantics>
</math></span><img src="./68b476cbf348bba38db1406ab1b40278996a8bfa.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -3.671ex; width:16.167ex; height:7.009ex;" alt="{\displaystyle \ {\mathcal {C}}={\frac {4\pi \varepsilon }{\ {\frac {1}{R_{1}}}-{\frac {1}{R_{2}}}\ }}\ }" loading="lazy"></span>
</td>
<td><span typeof="mw:File"></span>
<ul><li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle \varepsilon }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>ε<!-- ε --></mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle \varepsilon }</annotation>
</semantics>
</math></span><img src="./2193f5fc8a6dd05f24e01d0789b78ec2b57515ba.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.083ex; height:1.676ex;" alt="{\textstyle \varepsilon }" loading="lazy"></span>: <a href="Permittivity" title="Permittivity">Permittivity</a></li></ul>
</td></tr>
<tr>
<th>Two spheres,<br>equal radius<sup id="cite_ref-Maxwell_1873_266_ff_16-0" class="reference"><a href="#cite_note-Maxwell_1873_266_ff-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup>
</th>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\begin{aligned}\ {\mathcal {C}}\ =&\ {}2\pi \varepsilon a\ \sum _{n=1}^{\infty }{\frac {\sinh \left(\ln \left(D+{\sqrt {D^{2}-1}}\right)\right)}{\sinh \left(n\ln \left(D+{\sqrt {D^{2}-1}}\right)\right)}}\\={}&{}2\pi \varepsilon a\left[1+{\frac {1}{2D}}+{\frac {1}{4D^{2}}}+{\frac {1}{8D^{3}}}+{\frac {1}{8D^{4}}}+{\frac {3}{32D^{5}}}+{\mathcal {O}}\left({\frac {1}{D^{6}}}\right)\right]\\={}&{}2\pi \varepsilon a\left[\ln 2+\gamma -{\frac {1}{2}}\ln \left(2D-2\right)+{\mathcal {O}}\left(2D-2\right)\right]\\={}&{}2\pi \varepsilon a\,{\frac {\sqrt {D^{2}-1}}{\log(q)}}\left[\psi _{q}\left(1+{\frac {i\pi }{\log(q)}}\right)-i\pi -\psi _{q}(1)\right]\end{aligned}}\ }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mrow class="MJX-TeXAtom-ORD">
<mtable columnalign="right left right left right left right left right left right left" rowspacing="3pt" columnspacing="0em 2em 0em 2em 0em 2em 0em 2em 0em 2em 0em" displaystyle="true">
<mtr>
<mtd>
<mtext> </mtext>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mi class="MJX-tex-caligraphic" mathvariant="script">C</mi>
</mrow>
</mrow>
<mtext> </mtext>
<mo>=</mo>
</mtd>
<mtd>
<mtext> </mtext>
<mrow class="MJX-TeXAtom-ORD">
</mrow>
<mn>2</mn>
<mi>π<!-- π --></mi>
<mi>ε<!-- ε --></mi>
<mi>a</mi>
<mtext> </mtext>
<munderover>
<mo>∑<!-- ∑ --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mi>n</mi>
<mo>=</mo>
<mn>1</mn>
</mrow>
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">∞<!-- ∞ --></mi>
</mrow>
</munderover>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi>sinh</mi>
<mo><!-- --></mo>
<mrow>
<mo>(</mo>
<mrow>
<mi>ln</mi>
<mo><!-- --></mo>
<mrow>
<mo>(</mo>
<mrow>
<mi>D</mi>
<mo>+</mo>
<mrow class="MJX-TeXAtom-ORD">
<msqrt>
<msup>
<mi>D</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mo>−<!-- − --></mo>
<mn>1</mn>
</msqrt>
</mrow>
</mrow>
<mo>)</mo>
</mrow>
</mrow>
<mo>)</mo>
</mrow>
</mrow>
<mrow>
<mi>sinh</mi>
<mo><!-- --></mo>
<mrow>
<mo>(</mo>
<mrow>
<mi>n</mi>
<mi>ln</mi>
<mo><!-- --></mo>
<mrow>
<mo>(</mo>
<mrow>
<mi>D</mi>
<mo>+</mo>
<mrow class="MJX-TeXAtom-ORD">
<msqrt>
<msup>
<mi>D</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mo>−<!-- − --></mo>
<mn>1</mn>
</msqrt>
</mrow>
</mrow>
<mo>)</mo>
</mrow>
</mrow>
<mo>)</mo>
</mrow>
</mrow>
</mfrac>
</mrow>
</mtd>
</mtr>
<mtr>
<mtd>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
</mrow>
</mtd>
<mtd>
<mrow class="MJX-TeXAtom-ORD">
</mrow>
<mn>2</mn>
<mi>π<!-- π --></mi>
<mi>ε<!-- ε --></mi>
<mi>a</mi>
<mrow>
<mo>[</mo>
<mrow>
<mn>1</mn>
<mo>+</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>1</mn>
<mrow>
<mn>2</mn>
<mi>D</mi>
</mrow>
</mfrac>
</mrow>
<mo>+</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>1</mn>
<mrow>
<mn>4</mn>
<msup>
<mi>D</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
</mrow>
</mfrac>
</mrow>
<mo>+</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>1</mn>
<mrow>
<mn>8</mn>
<msup>
<mi>D</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>3</mn>
</mrow>
</msup>
</mrow>
</mfrac>
</mrow>
<mo>+</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>1</mn>
<mrow>
<mn>8</mn>
<msup>
<mi>D</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>4</mn>
</mrow>
</msup>
</mrow>
</mfrac>
</mrow>
<mo>+</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>3</mn>
<mrow>
<mn>32</mn>
<msup>
<mi>D</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>5</mn>
</mrow>
</msup>
</mrow>
</mfrac>
</mrow>
<mo>+</mo>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mi class="MJX-tex-caligraphic" mathvariant="script">O</mi>
</mrow>
</mrow>
<mrow>
<mo>(</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>1</mn>
<msup>
<mi>D</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>6</mn>
</mrow>
</msup>
</mfrac>
</mrow>
<mo>)</mo>
</mrow>
</mrow>
<mo>]</mo>
</mrow>
</mtd>
</mtr>
<mtr>
<mtd>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
</mrow>
</mtd>
<mtd>
<mrow class="MJX-TeXAtom-ORD">
</mrow>
<mn>2</mn>
<mi>π<!-- π --></mi>
<mi>ε<!-- ε --></mi>
<mi>a</mi>
<mrow>
<mo>[</mo>
<mrow>
<mi>ln</mi>
<mo><!-- --></mo>
<mn>2</mn>
<mo>+</mo>
<mi>γ<!-- γ --></mi>
<mo>−<!-- − --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>1</mn>
<mn>2</mn>
</mfrac>
</mrow>
<mi>ln</mi>
<mo><!-- --></mo>
<mrow>
<mo>(</mo>
<mrow>
<mn>2</mn>
<mi>D</mi>
<mo>−<!-- − --></mo>
<mn>2</mn>
</mrow>
<mo>)</mo>
</mrow>
<mo>+</mo>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mi class="MJX-tex-caligraphic" mathvariant="script">O</mi>
</mrow>
</mrow>
<mrow>
<mo>(</mo>
<mrow>
<mn>2</mn>
<mi>D</mi>
<mo>−<!-- − --></mo>
<mn>2</mn>
</mrow>
<mo>)</mo>
</mrow>
</mrow>
<mo>]</mo>
</mrow>
</mtd>
</mtr>
<mtr>
<mtd>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
</mrow>
</mtd>
<mtd>
<mrow class="MJX-TeXAtom-ORD">
</mrow>
<mn>2</mn>
<mi>π<!-- π --></mi>
<mi>ε<!-- ε --></mi>
<mi>a</mi>
<mspace width="thinmathspace"></mspace>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<msqrt>
<msup>
<mi>D</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mo>−<!-- − --></mo>
<mn>1</mn>
</msqrt>
<mrow>
<mi>log</mi>
<mo><!-- --></mo>
<mo stretchy="false">(</mo>
<mi>q</mi>
<mo stretchy="false">)</mo>
</mrow>
</mfrac>
</mrow>
<mrow>
<mo>[</mo>
<mrow>
<msub>
<mi>ψ<!-- ψ --></mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>q</mi>
</mrow>
</msub>
<mrow>
<mo>(</mo>
<mrow>
<mn>1</mn>
<mo>+</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi>i</mi>
<mi>π<!-- π --></mi>
</mrow>
<mrow>
<mi>log</mi>
<mo><!-- --></mo>
<mo stretchy="false">(</mo>
<mi>q</mi>
<mo stretchy="false">)</mo>
</mrow>
</mfrac>
</mrow>
</mrow>
<mo>)</mo>
</mrow>
<mo>−<!-- − --></mo>
<mi>i</mi>
<mi>π<!-- π --></mi>
<mo>−<!-- − --></mo>
<msub>
<mi>ψ<!-- ψ --></mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>q</mi>
</mrow>
</msub>
<mo stretchy="false">(</mo>
<mn>1</mn>
<mo stretchy="false">)</mo>
</mrow>
<mo>]</mo>
</mrow>
</mtd>
</mtr>
</mtable>
</mrow>
<mtext> </mtext>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle {\begin{aligned}\ {\mathcal {C}}\ =&\ {}2\pi \varepsilon a\ \sum _{n=1}^{\infty }{\frac {\sinh \left(\ln \left(D+{\sqrt {D^{2}-1}}\right)\right)}{\sinh \left(n\ln \left(D+{\sqrt {D^{2}-1}}\right)\right)}}\\={}&{}2\pi \varepsilon a\left[1+{\frac {1}{2D}}+{\frac {1}{4D^{2}}}+{\frac {1}{8D^{3}}}+{\frac {1}{8D^{4}}}+{\frac {3}{32D^{5}}}+{\mathcal {O}}\left({\frac {1}{D^{6}}}\right)\right]\\={}&{}2\pi \varepsilon a\left[\ln 2+\gamma -{\frac {1}{2}}\ln \left(2D-2\right)+{\mathcal {O}}\left(2D-2\right)\right]\\={}&{}2\pi \varepsilon a\,{\frac {\sqrt {D^{2}-1}}{\log(q)}}\left[\psi _{q}\left(1+{\frac {i\pi }{\log(q)}}\right)-i\pi -\psi _{q}(1)\right]\end{aligned}}\ }</annotation>
</semantics>
</math></span><img src="./b633a8a25dbe55de0e323c5ca869ab2e6c78b1e6.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -14.338ex; width:66.507ex; height:29.843ex;" alt="{\displaystyle {\begin{aligned}\ {\mathcal {C}}\ =&\ {}2\pi \varepsilon a\ \sum _{n=1}^{\infty }{\frac {\sinh \left(\ln \left(D+{\sqrt {D^{2}-1}}\right)\right)}{\sinh \left(n\ln \left(D+{\sqrt {D^{2}-1}}\right)\right)}}\\={}&{}2\pi \varepsilon a\left[1+{\frac {1}{2D}}+{\frac {1}{4D^{2}}}+{\frac {1}{8D^{3}}}+{\frac {1}{8D^{4}}}+{\frac {3}{32D^{5}}}+{\mathcal {O}}\left({\frac {1}{D^{6}}}\right)\right]\\={}&{}2\pi \varepsilon a\left[\ln 2+\gamma -{\frac {1}{2}}\ln \left(2D-2\right)+{\mathcal {O}}\left(2D-2\right)\right]\\={}&{}2\pi \varepsilon a\,{\frac {\sqrt {D^{2}-1}}{\log(q)}}\left[\psi _{q}\left(1+{\frac {i\pi }{\log(q)}}\right)-i\pi -\psi _{q}(1)\right]\end{aligned}}\ }" loading="lazy"></span>
</td>
<td>
<ul><li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle a}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>a</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle a}</annotation>
</semantics>
</math></span><img src="./7a503f107a7c104e40e484cee9e1f5993d28ffd8.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.23ex; height:1.676ex;" alt="{\textstyle a}" loading="lazy"></span>: Radius</li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle d}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>d</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle d}</annotation>
</semantics>
</math></span><img src="./252135f29da0e9f9e130ff2d53be5df2f7044d99.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.216ex; height:2.176ex;" alt="{\textstyle d}" loading="lazy"></span>: Distance, <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle d>2a}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>d</mi>
<mo>></mo>
<mn>2</mn>
<mi>a</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle d>2a}</annotation>
</semantics>
</math></span><img src="./814d16cd28ad50bd8b83a9cf68d15667342e63f6.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:6.707ex; height:2.176ex;" alt="{\textstyle d>2a}" loading="lazy"></span></li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle D=d/2a,D>1}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>D</mi>
<mo>=</mo>
<mi>d</mi>
<mrow class="MJX-TeXAtom-ORD">
<mo>/</mo>
</mrow>
<mn>2</mn>
<mi>a</mi>
<mo>,</mo>
<mi>D</mi>
<mo>></mo>
<mn>1</mn>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle D=d/2a,D>1}</annotation>
</semantics>
</math></span><img src="./90498f0ee5fc403de434b4e329c2d2255635bf6c.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:17.012ex; height:2.843ex;" alt="{\textstyle D=d/2a,D>1}" loading="lazy"></span></li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle \gamma }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="false" scriptlevel="0">
<mi>γ<!-- γ --></mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\textstyle \gamma }</annotation>
</semantics>
</math></span><img src="./079fa214f0d7f7dcf92af4c520c95aa7ca787d1b.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:1.262ex; height:2.176ex;" alt="{\textstyle \gamma }" loading="lazy"></span>: <a href="Euler%E2%80%93Mascheroni_constant" class="mw-redirect" title="Euler–Mascheroni constant">Euler's constant</a></li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle q=D+{\sqrt {D^{2}-1}}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>q</mi>
<mo>=</mo>
<mi>D</mi>
<mo>+</mo>
<mrow class="MJX-TeXAtom-ORD">
<msqrt>
<msup>
<mi>D</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mo>−<!-- − --></mo>
<mn>1</mn>
</msqrt>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle q=D+{\sqrt {D^{2}-1}}}</annotation>
</semantics>
</math></span><img src="./3b27f407e95b1c34a20dc36666c8722c19a3fa0b.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:18.238ex; height:3.509ex;" alt="{\displaystyle q=D+{\sqrt {D^{2}-1}}}" loading="lazy"></span></li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \psi _{q}(z)={\frac {\partial _{z}\Gamma _{q}(z)}{\Gamma _{q}(z)}}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>ψ<!-- ψ --></mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>q</mi>
</mrow>
</msub>
<mo stretchy="false">(</mo>
<mi>z</mi>
<mo stretchy="false">)</mo>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<msub>
<mi mathvariant="normal">∂<!-- ∂ --></mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>z</mi>
</mrow>
</msub>
<msub>
<mi mathvariant="normal">Γ<!-- Γ --></mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>q</mi>
</mrow>
</msub>
<mo stretchy="false">(</mo>
<mi>z</mi>
<mo stretchy="false">)</mo>
</mrow>
<mrow>
<msub>
<mi mathvariant="normal">Γ<!-- Γ --></mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>q</mi>
</mrow>
</msub>
<mo stretchy="false">(</mo>
<mi>z</mi>
<mo stretchy="false">)</mo>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \psi _{q}(z)={\frac {\partial _{z}\Gamma _{q}(z)}{\Gamma _{q}(z)}}}</annotation>
</semantics>
</math></span><img src="./6a2d70840f1445b3601ac1112cc7f2e83f2a6292.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.671ex; width:16.909ex; height:6.509ex;" alt="{\displaystyle \psi _{q}(z)={\frac {\partial _{z}\Gamma _{q}(z)}{\Gamma _{q}(z)}}}" loading="lazy"></span>: the q-digamma function</li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \Gamma _{q}(z)}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi mathvariant="normal">Γ<!-- Γ --></mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>q</mi>
</mrow>
</msub>
<mo stretchy="false">(</mo>
<mi>z</mi>
<mo stretchy="false">)</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \Gamma _{q}(z)}</annotation>
</semantics>
</math></span><img src="./1013a7187dcbf7518dd1514b1c2de420c9f555cc.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:5.339ex; height:3.009ex;" alt="{\displaystyle \Gamma _{q}(z)}" loading="lazy"></span>: the <a href="Q-gamma_function" title="Q-gamma function">q-gamma function</a><sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup></li></ul>
<p>See also <a href="Basic_hypergeometric_series" title="Basic hypergeometric series">Basic hypergeometric series</a>.
</p>
</td></tr>
<tr>
<th>Sphere in front of wall<sup id="cite_ref-Maxwell_1873_266_ff_16-1" class="reference"><a href="#cite_note-Maxwell_1873_266_ff-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup>
</th>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \ {\mathcal {C}}=4\pi \varepsilon a\sum _{n=1}^{\infty }{\frac {\sinh \left(\ln \left(D+{\sqrt {D^{2}-1}}\right)\right)}{\sinh \left(n\ln \left(D+{\sqrt {D^{2}-1}}\right)\right)}}\ }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mtext> </mtext>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mi class="MJX-tex-caligraphic" mathvariant="script">C</mi>
</mrow>
</mrow>
<mo>=</mo>
<mn>4</mn>
<mi>π<!-- π --></mi>
<mi>ε<!-- ε --></mi>
<mi>a</mi>
<munderover>
<mo>∑<!-- ∑ --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mi>n</mi>
<mo>=</mo>
<mn>1</mn>
</mrow>
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">∞<!-- ∞ --></mi>
</mrow>
</munderover>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi>sinh</mi>
<mo><!-- --></mo>
<mrow>
<mo>(</mo>
<mrow>
<mi>ln</mi>
<mo><!-- --></mo>
<mrow>
<mo>(</mo>
<mrow>
<mi>D</mi>
<mo>+</mo>
<mrow class="MJX-TeXAtom-ORD">
<msqrt>
<msup>
<mi>D</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mo>−<!-- − --></mo>
<mn>1</mn>
</msqrt>
</mrow>
</mrow>
<mo>)</mo>
</mrow>
</mrow>
<mo>)</mo>
</mrow>
</mrow>
<mrow>
<mi>sinh</mi>
<mo><!-- --></mo>
<mrow>
<mo>(</mo>
<mrow>
<mi>n</mi>
<mi>ln</mi>
<mo><!-- --></mo>
<mrow>
<mo>(</mo>
<mrow>
<mi>D</mi>
<mo>+</mo>
<mrow class="MJX-TeXAtom-ORD">
<msqrt>
<msup>
<mi>D</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mo>−<!-- − --></mo>
<mn>1</mn>
</msqrt>
</mrow>
</mrow>
<mo>)</mo>
</mrow>
</mrow>
<mo>)</mo>
</mrow>
</mrow>
</mfrac>
</mrow>
<mtext> </mtext>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \ {\mathcal {C}}=4\pi \varepsilon a\sum _{n=1}^{\infty }{\frac {\sinh \left(\ln \left(D+{\sqrt {D^{2}-1}}\right)\right)}{\sinh \left(n\ln \left(D+{\sqrt {D^{2}-1}}\right)\right)}}\ }</annotation>
</semantics>
</math></span><img src="./a4c499a0a2bd13db98ec1cc5ba4f27ccb0ef98a0.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -4.505ex; width:42.762ex; height:10.176ex;" alt="{\displaystyle \ {\mathcal {C}}=4\pi \varepsilon a\sum _{n=1}^{\infty }{\frac {\sinh \left(\ln \left(D+{\sqrt {D^{2}-1}}\right)\right)}{\sinh \left(n\ln \left(D+{\sqrt {D^{2}-1}}\right)\right)}}\ }" loading="lazy"></span>
</td>
<td>
<ul><li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \ a\ }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mtext> </mtext>
<mi>a</mi>
<mtext> </mtext>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \ a\ }</annotation>
</semantics>
</math></span><img src="./8124de742ae987fe73be9ca9d3d4ba8586e28b11.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.391ex; height:1.676ex;" alt="{\displaystyle \ a\ }" loading="lazy"></span>: Radius</li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \ d\ }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mtext> </mtext>
<mi>d</mi>
<mtext> </mtext>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \ d\ }</annotation>
</semantics>
</math></span><img src="./3035fc0c2be984029a7ef81eb60f13c26b0c6ed5.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.377ex; height:2.176ex;" alt="{\displaystyle \ d\ }" loading="lazy"></span>: Distance, <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle d>a}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>d</mi>
<mo>></mo>
<mi>a</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle d>a}</annotation>
</semantics>
</math></span><img src="./5a63ce3b01161f8f4a757d6d8e0408dcdbe5b478.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:5.544ex; height:2.176ex;" alt="{\displaystyle d>a}" loading="lazy"></span></li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle D=d/a}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>D</mi>
<mo>=</mo>
<mi>d</mi>
<mrow class="MJX-TeXAtom-ORD">
<mo>/</mo>
</mrow>
<mi>a</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle D=d/a}</annotation>
</semantics>
</math></span><img src="./557cc492f07e952b74c8d82406d38cbaeb9a4dab.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:8.631ex; height:2.843ex;" alt="{\displaystyle D=d/a}" loading="lazy"></span></li></ul>
</td></tr>
<tr>
<th>Sphere
</th>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \ {\mathcal {C}}=4\pi \varepsilon a\ }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mtext> </mtext>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mi class="MJX-tex-caligraphic" mathvariant="script">C</mi>
</mrow>
</mrow>
<mo>=</mo>
<mn>4</mn>
<mi>π<!-- π --></mi>
<mi>ε<!-- ε --></mi>
<mi>a</mi>
<mtext> </mtext>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \ {\mathcal {C}}=4\pi \varepsilon a\ }</annotation>
</semantics>
</math></span><img src="./efd5eb04590b5ea11104a39d181e781086360d6f.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:10.307ex; height:2.176ex;" alt="{\displaystyle \ {\mathcal {C}}=4\pi \varepsilon a\ }" loading="lazy"></span>
</td>
<td>
<ul><li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle a}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>a</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle a}</annotation>
</semantics>
</math></span><img src="./ffd2487510aa438433a2579450ab2b3d557e5edc.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.23ex; height:1.676ex;" alt="{\displaystyle a}" loading="lazy"></span>: Radius</li></ul>
</td></tr>
<tr>
<th>Circular disc<sup id="cite_ref-Jackson_1975_128_19-0" class="reference"><a href="#cite_note-Jackson_1975_128-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup>
</th>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \ {\mathcal {C}}=8\varepsilon a\ }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mtext> </mtext>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mi class="MJX-tex-caligraphic" mathvariant="script">C</mi>
</mrow>
</mrow>
<mo>=</mo>
<mn>8</mn>
<mi>ε<!-- ε --></mi>
<mi>a</mi>
<mtext> </mtext>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \ {\mathcal {C}}=8\varepsilon a\ }</annotation>
</semantics>
</math></span><img src="./f55ed23a0dd0dbcd71b5dd780c08fe6725ceb68e.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:8.975ex; height:2.176ex;" alt="{\displaystyle \ {\mathcal {C}}=8\varepsilon a\ }" loading="lazy"></span>
</td>
<td>
<ul><li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle a}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>a</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle a}</annotation>
</semantics>
</math></span><img src="./ffd2487510aa438433a2579450ab2b3d557e5edc.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.23ex; height:1.676ex;" alt="{\displaystyle a}" loading="lazy"></span>: Radius</li></ul>
</td></tr>
<tr>
<th>Thin straight wire,<br> finite length<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup>
</th>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \ {\mathcal {C}}={\frac {2\pi \varepsilon \ell }{\Lambda }}\left[1+{\frac {1}{\Lambda }}\left(1-\ln 2\right)+{\frac {1}{\Lambda ^{2}}}\left(1+\left(1-\ln 2\right)^{2}-{\frac {\pi ^{2}}{12}}\right)+{\mathcal {O}}\left({\frac {1}{\Lambda ^{3}}}\right)\right]\ }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mtext> </mtext>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mi class="MJX-tex-caligraphic" mathvariant="script">C</mi>
</mrow>
</mrow>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mn>2</mn>
<mi>π<!-- π --></mi>
<mi>ε<!-- ε --></mi>
<mi>ℓ<!-- ℓ --></mi>
</mrow>
<mi mathvariant="normal">Λ<!-- Λ --></mi>
</mfrac>
</mrow>
<mrow>
<mo>[</mo>
<mrow>
<mn>1</mn>
<mo>+</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>1</mn>
<mi mathvariant="normal">Λ<!-- Λ --></mi>
</mfrac>
</mrow>
<mrow>
<mo>(</mo>
<mrow>
<mn>1</mn>
<mo>−<!-- − --></mo>
<mi>ln</mi>
<mo><!-- --></mo>
<mn>2</mn>
</mrow>
<mo>)</mo>
</mrow>
<mo>+</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>1</mn>
<msup>
<mi mathvariant="normal">Λ<!-- Λ --></mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
</mfrac>
</mrow>
<mrow>
<mo>(</mo>
<mrow>
<mn>1</mn>
<mo>+</mo>
<msup>
<mrow>
<mo>(</mo>
<mrow>
<mn>1</mn>
<mo>−<!-- − --></mo>
<mi>ln</mi>
<mo><!-- --></mo>
<mn>2</mn>
</mrow>
<mo>)</mo>
</mrow>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mo>−<!-- − --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<msup>
<mi>π<!-- π --></mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mn>12</mn>
</mfrac>
</mrow>
</mrow>
<mo>)</mo>
</mrow>
<mo>+</mo>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mi class="MJX-tex-caligraphic" mathvariant="script">O</mi>
</mrow>
</mrow>
<mrow>
<mo>(</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>1</mn>
<msup>
<mi mathvariant="normal">Λ<!-- Λ --></mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>3</mn>
</mrow>
</msup>
</mfrac>
</mrow>
<mo>)</mo>
</mrow>
</mrow>
<mo>]</mo>
</mrow>
<mtext> </mtext>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \ {\mathcal {C}}={\frac {2\pi \varepsilon \ell }{\Lambda }}\left[1+{\frac {1}{\Lambda }}\left(1-\ln 2\right)+{\frac {1}{\Lambda ^{2}}}\left(1+\left(1-\ln 2\right)^{2}-{\frac {\pi ^{2}}{12}}\right)+{\mathcal {O}}\left({\frac {1}{\Lambda ^{3}}}\right)\right]\ }</annotation>
</semantics>
</math></span><img src="./3bcd1ed9c0ea246c62f8705fb162f3e2b50ccd85.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:72.829ex; height:6.343ex;" alt="{\displaystyle \ {\mathcal {C}}={\frac {2\pi \varepsilon \ell }{\Lambda }}\left[1+{\frac {1}{\Lambda }}\left(1-\ln 2\right)+{\frac {1}{\Lambda ^{2}}}\left(1+\left(1-\ln 2\right)^{2}-{\frac {\pi ^{2}}{12}}\right)+{\mathcal {O}}\left({\frac {1}{\Lambda ^{3}}}\right)\right]\ }" loading="lazy"></span>
</td>
<td>
<ul><li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle a}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>a</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle a}</annotation>
</semantics>
</math></span><img src="./ffd2487510aa438433a2579450ab2b3d557e5edc.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.23ex; height:1.676ex;" alt="{\displaystyle a}" loading="lazy"></span>: Wire radius</li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \ell }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>ℓ<!-- ℓ --></mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \ell }</annotation>
</semantics>
</math></span><img src="./f066e981e530bacc07efc6a10fa82deee985929e.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:0.97ex; height:2.176ex;" alt="{\displaystyle \ell }" loading="lazy"></span>: Length</li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \ \Lambda =\ln \left(\ell /a\right)\ }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mtext> </mtext>
<mi mathvariant="normal">Λ<!-- Λ --></mi>
<mo>=</mo>
<mi>ln</mi>
<mo><!-- --></mo>
<mrow>
<mo>(</mo>
<mrow>
<mi>ℓ<!-- ℓ --></mi>
<mrow class="MJX-TeXAtom-ORD">
<mo>/</mo>
</mrow>
<mi>a</mi>
</mrow>
<mo>)</mo>
</mrow>
<mtext> </mtext>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \ \Lambda =\ln \left(\ell /a\right)\ }</annotation>
</semantics>
</math></span><img src="./60e1931b394c02c33a3fd4153d2997590c865dfc.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:12.983ex; height:2.843ex;" alt="{\displaystyle \ \Lambda =\ln \left(\ell /a\right)\ }" loading="lazy"></span></li></ul>
</td></tr></tbody></table>
<div class="mw-heading mw-heading2"><h2 id="Energy_storage">Energy storage</h2></div>
<p>The <a href="Energy" title="Energy">energy</a> (measured in <a href="Joule" title="Joule">joules</a>) stored in a capacitor is equal to the <i>work</i> required to push the charges into the capacitor, i.e. to charge it. Consider a capacitor of capacitance <i>C</i>, holding a charge +<i>q</i> on one plate and −<i>q</i> on the other. Moving a small element of charge d<i>q</i> from one plate to the other against the potential difference <span class="nowrap"><i>V</i> = <i>q</i>/<i>C</i></span> requires the work d<i>W</i>:
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \mathrm {d} W={\frac {q}{C}}\,\mathrm {d} q,}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">d</mi>
</mrow>
<mi>W</mi>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mi>q</mi>
<mi>C</mi>
</mfrac>
</mrow>
<mspace width="thinmathspace"></mspace>
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">d</mi>
</mrow>
<mi>q</mi>
<mo>,</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \mathrm {d} W={\frac {q}{C}}\,\mathrm {d} q,}</annotation>
</semantics>
</math></span></span>
where <i>W</i> is the work measured in joules, <i>q</i> is the charge measured in coulombs and <i>C</i> is the capacitance, measured in farads.
</p><p>The energy stored in a capacitor is found by <a href="Integral" title="Integral">integrating</a> this equation. Starting with an uncharged capacitance (<span class="nowrap"><i>q</i> = 0</span>) and moving charge from one plate to the other until the plates have charge +<i>Q</i> and −<i>Q</i> requires the work <i>W</i>:
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle W_{\text{charging}}=\int _{0}^{Q}{\frac {q}{C}}\,\mathrm {d} q={\frac {1}{2}}{\frac {Q^{2}}{C}}={\frac {1}{2}}QV={\frac {1}{2}}CV^{2}=W_{\text{stored}}.}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>W</mi>
<mrow class="MJX-TeXAtom-ORD">
<mtext>charging</mtext>
</mrow>
</msub>
<mo>=</mo>
<msubsup>
<mo>∫<!-- ∫ --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mn>0</mn>
</mrow>
<mrow class="MJX-TeXAtom-ORD">
<mi>Q</mi>
</mrow>
</msubsup>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mi>q</mi>
<mi>C</mi>
</mfrac>
</mrow>
<mspace width="thinmathspace"></mspace>
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">d</mi>
</mrow>
<mi>q</mi>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>1</mn>
<mn>2</mn>
</mfrac>
</mrow>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<msup>
<mi>Q</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mi>C</mi>
</mfrac>
</mrow>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>1</mn>
<mn>2</mn>
</mfrac>
</mrow>
<mi>Q</mi>
<mi>V</mi>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>1</mn>
<mn>2</mn>
</mfrac>
</mrow>
<mi>C</mi>
<msup>
<mi>V</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mo>=</mo>
<msub>
<mi>W</mi>
<mrow class="MJX-TeXAtom-ORD">
<mtext>stored</mtext>
</mrow>
</msub>
<mo>.</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle W_{\text{charging}}=\int _{0}^{Q}{\frac {q}{C}}\,\mathrm {d} q={\frac {1}{2}}{\frac {Q^{2}}{C}}={\frac {1}{2}}QV={\frac {1}{2}}CV^{2}=W_{\text{stored}}.}</annotation>
</semantics>
</math></span></span>
</p>
<div class="mw-heading mw-heading2"><h2 id="Nanoscale_systems">Nanoscale systems</h2></div>
<p>The capacitance of nanoscale dielectric capacitors such as <a href="Quantum_dots" class="mw-redirect" title="Quantum dots">quantum dots</a> may differ from conventional formulations of larger capacitors. In particular, the electrostatic potential difference experienced by electrons in conventional capacitors is spatially well-defined and fixed by the shape and size of metallic electrodes in addition to the statistically large number of electrons present in conventional capacitors. In nanoscale capacitors, however, the electrostatic potentials experienced by electrons are determined by the number and locations of all electrons that contribute to the electronic properties of the device. In such devices, the number of electrons may be very small, so the resulting spatial distribution of equipotential surfaces within the device is exceedingly complex.
</p>
<div class="mw-heading mw-heading3"><h3 id="Single-electron_devices">Single-electron devices</h3></div>
<p>The capacitance of a connected, or "closed", single-electron device is twice the capacitance of an unconnected, or "open", single-electron device.<sup id="cite_ref-Tsu_23-0" class="reference"><a href="#cite_note-Tsu-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> This fact may be traced more fundamentally to the energy stored in the single-electron device whose "direct polarization" interaction energy may be equally divided into the interaction of the electron with the polarized charge on the device itself due to the presence of the electron and the amount of potential energy required to form the polarized charge on the device (the interaction of charges in the device's dielectric material with the potential due to the electron).<sup id="cite_ref-LaFave-DCD_24-0" class="reference"><a href="#cite_note-LaFave-DCD-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup>
</p>
<div class="mw-heading mw-heading3"><h3 id="Few-electron_devices">Few-electron devices</h3></div>
<p>The derivation of a "quantum capacitance" of a few-electron device involves the thermodynamic <a href="Chemical_potential" title="Chemical potential">chemical potential</a> of an <i>N</i>-particle system given by
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \mu (N)=U(N)-U(N-1),}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>μ<!-- μ --></mi>
<mo stretchy="false">(</mo>
<mi>N</mi>
<mo stretchy="false">)</mo>
<mo>=</mo>
<mi>U</mi>
<mo stretchy="false">(</mo>
<mi>N</mi>
<mo stretchy="false">)</mo>
<mo>−<!-- − --></mo>
<mi>U</mi>
<mo stretchy="false">(</mo>
<mi>N</mi>
<mo>−<!-- − --></mo>
<mn>1</mn>
<mo stretchy="false">)</mo>
<mo>,</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \mu (N)=U(N)-U(N-1),}</annotation>
</semantics>
</math></span></span>
</p><p>whose energy terms may be obtained as solutions of the <a href="Schr%C3%B6dinger_equation" title="Schrödinger equation">Schrödinger equation</a>. The definition of capacitance,
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {1 \over C}\equiv {\Delta V \over \Delta Q},}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>1</mn>
<mi>C</mi>
</mfrac>
</mrow>
<mo>≡<!-- ≡ --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi mathvariant="normal">Δ<!-- Δ --></mi>
<mi>V</mi>
</mrow>
<mrow>
<mi mathvariant="normal">Δ<!-- Δ --></mi>
<mi>Q</mi>
</mrow>
</mfrac>
</mrow>
<mo>,</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle {1 \over C}\equiv {\Delta V \over \Delta Q},}</annotation>
</semantics>
</math></span></span>
with the potential difference
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \Delta V={\Delta \mu \, \over e}={\mu (N+\Delta N)-\mu (N) \over e}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Δ<!-- Δ --></mi>
<mi>V</mi>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi mathvariant="normal">Δ<!-- Δ --></mi>
<mi>μ<!-- μ --></mi>
<mspace width="thinmathspace"></mspace>
</mrow>
<mi>e</mi>
</mfrac>
</mrow>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi>μ<!-- μ --></mi>
<mo stretchy="false">(</mo>
<mi>N</mi>
<mo>+</mo>
<mi mathvariant="normal">Δ<!-- Δ --></mi>
<mi>N</mi>
<mo stretchy="false">)</mo>
<mo>−<!-- − --></mo>
<mi>μ<!-- μ --></mi>
<mo stretchy="false">(</mo>
<mi>N</mi>
<mo stretchy="false">)</mo>
</mrow>
<mi>e</mi>
</mfrac>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \Delta V={\Delta \mu \, \over e}={\mu (N+\Delta N)-\mu (N) \over e}}</annotation>
</semantics>
</math></span></span>
</p><p>may be applied to the device with the addition or removal of individual electrons,
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \Delta N=1}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Δ<!-- Δ --></mi>
<mi>N</mi>
<mo>=</mo>
<mn>1</mn>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \Delta N=1}</annotation>
</semantics>
</math></span></span> and <span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \Delta Q=e.}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Δ<!-- Δ --></mi>
<mi>Q</mi>
<mo>=</mo>
<mi>e</mi>
<mo>.</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \Delta Q=e.}</annotation>
</semantics>
</math></span></span>
</p><p>The "quantum capacitance" of the device is then<sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup>
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C_{Q}(N)={\frac {e^{2}}{\mu (N+1)-\mu (N)}}={\frac {e^{2}}{E(N)}}.}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>C</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>Q</mi>
</mrow>
</msub>
<mo stretchy="false">(</mo>
<mi>N</mi>
<mo stretchy="false">)</mo>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<msup>
<mi>e</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mrow>
<mi>μ<!-- μ --></mi>
<mo stretchy="false">(</mo>
<mi>N</mi>
<mo>+</mo>
<mn>1</mn>
<mo stretchy="false">)</mo>
<mo>−<!-- − --></mo>
<mi>μ<!-- μ --></mi>
<mo stretchy="false">(</mo>
<mi>N</mi>
<mo stretchy="false">)</mo>
</mrow>
</mfrac>
</mrow>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<msup>
<mi>e</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mrow>
<mi>E</mi>
<mo stretchy="false">(</mo>
<mi>N</mi>
<mo stretchy="false">)</mo>
</mrow>
</mfrac>
</mrow>
<mo>.</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle C_{Q}(N)={\frac {e^{2}}{\mu (N+1)-\mu (N)}}={\frac {e^{2}}{E(N)}}.}</annotation>
</semantics>
</math></span></span>
</p><p>This expression of "quantum capacitance" may be written as
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C_{Q}(N)={e^{2} \over U(N)},}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>C</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>Q</mi>
</mrow>
</msub>
<mo stretchy="false">(</mo>
<mi>N</mi>
<mo stretchy="false">)</mo>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<msup>
<mi>e</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mrow>
<mi>U</mi>
<mo stretchy="false">(</mo>
<mi>N</mi>
<mo stretchy="false">)</mo>
</mrow>
</mfrac>
</mrow>
<mo>,</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle C_{Q}(N)={e^{2} \over U(N)},}</annotation>
</semantics>
</math></span></span>
which differs from the conventional expression described in the introduction where <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle W_{\text{stored}}=U}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>W</mi>
<mrow class="MJX-TeXAtom-ORD">
<mtext>stored</mtext>
</mrow>
</msub>
<mo>=</mo>
<mi>U</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle W_{\text{stored}}=U}</annotation>
</semantics>
</math></span><img src="./4e9781e1e1b0249d5008608bad4f9282ba9d4c28.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:11.705ex; height:2.509ex;" alt="{\displaystyle W_{\text{stored}}=U}" loading="lazy"></span>, the stored electrostatic potential energy,
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C={Q^{2} \over 2U},}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>C</mi>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<msup>
<mi>Q</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mrow>
<mn>2</mn>
<mi>U</mi>
</mrow>
</mfrac>
</mrow>
<mo>,</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle C={Q^{2} \over 2U},}</annotation>
</semantics>
</math></span></span>
by a factor of <span class="sfrac"><span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">2</span></span></span> with <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle Q=Ne}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>Q</mi>
<mo>=</mo>
<mi>N</mi>
<mi>e</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle Q=Ne}</annotation>
</semantics>
</math></span><img src="./b233ed65ba48267c49f94df7c9a0e43c7bda72dc.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:8.084ex; height:2.509ex;" alt="{\displaystyle Q=Ne}" loading="lazy"></span>.
</p><p>However, within the framework of purely classical electrostatic interactions, the appearance of the factor of <span class="sfrac"><span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">2</span></span></span> is the result of integration in the conventional formulation involving the work done when charging a capacitor,
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle W_{\text{charging}}=U=\int _{0}^{Q}{\frac {q}{C}}\,\mathrm {d} q,}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>W</mi>
<mrow class="MJX-TeXAtom-ORD">
<mtext>charging</mtext>
</mrow>
</msub>
<mo>=</mo>
<mi>U</mi>
<mo>=</mo>
<msubsup>
<mo>∫<!-- ∫ --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mn>0</mn>
</mrow>
<mrow class="MJX-TeXAtom-ORD">
<mi>Q</mi>
</mrow>
</msubsup>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mi>q</mi>
<mi>C</mi>
</mfrac>
</mrow>
<mspace width="thinmathspace"></mspace>
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">d</mi>
</mrow>
<mi>q</mi>
<mo>,</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle W_{\text{charging}}=U=\int _{0}^{Q}{\frac {q}{C}}\,\mathrm {d} q,}</annotation>
</semantics>
</math></span></span>
</p><p>which is appropriate since <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \mathrm {d} q=0}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">d</mi>
</mrow>
<mi>q</mi>
<mo>=</mo>
<mn>0</mn>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \mathrm {d} q=0}</annotation>
</semantics>
</math></span><img src="./663c1866d01f78fe9a3c27af4741fcd7854936fe.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:6.623ex; height:2.509ex;" alt="{\displaystyle \mathrm {d} q=0}" loading="lazy"></span> for systems involving either many electrons or metallic electrodes, but in few-electron systems, <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \mathrm {d} q\to \Delta \,Q=e}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">d</mi>
</mrow>
<mi>q</mi>
<mo stretchy="false">→<!-- → --></mo>
<mi mathvariant="normal">Δ<!-- Δ --></mi>
<mspace width="thinmathspace"></mspace>
<mi>Q</mi>
<mo>=</mo>
<mi>e</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \mathrm {d} q\to \Delta \,Q=e}</annotation>
</semantics>
</math></span><img src="./7292acec444e6c365e2d528aa35cb5cac79fcf4a.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:14.319ex; height:2.509ex;" alt="{\displaystyle \mathrm {d} q\to \Delta \,Q=e}" loading="lazy"></span>. The integral generally becomes a summation. One may trivially combine the expressions of capacitance
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle Q=CV}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>Q</mi>
<mo>=</mo>
<mi>C</mi>
<mi>V</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle Q=CV}</annotation>
</semantics>
</math></span></span>
and electrostatic interaction energy,
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle U=QV,}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>U</mi>
<mo>=</mo>
<mi>Q</mi>
<mi>V</mi>
<mo>,</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle U=QV,}</annotation>
</semantics>
</math></span></span>
to obtain
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C=Q{1 \over V}=Q{Q \over U}={Q^{2} \over U},}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>C</mi>
<mo>=</mo>
<mi>Q</mi>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>1</mn>
<mi>V</mi>
</mfrac>
</mrow>
<mo>=</mo>
<mi>Q</mi>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mi>Q</mi>
<mi>U</mi>
</mfrac>
</mrow>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<msup>
<mi>Q</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mi>U</mi>
</mfrac>
</mrow>
<mo>,</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle C=Q{1 \over V}=Q{Q \over U}={Q^{2} \over U},}</annotation>
</semantics>
</math></span></span>
</p><p>which is similar to the quantum capacitance. A more rigorous derivation is reported in the literature.<sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> In particular, to circumvent the mathematical challenges of spatially complex equipotential surfaces within the device, an <i>average</i> electrostatic potential experienced by each electron is utilized in the derivation.
</p><p>Apparent mathematical differences may be understood more fundamentally. The potential energy, <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle U(N)}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>U</mi>
<mo stretchy="false">(</mo>
<mi>N</mi>
<mo stretchy="false">)</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle U(N)}</annotation>
</semantics>
</math></span><img src="./75bc0531863b76e4cb6239ccfc14804a5a817d1a.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:5.656ex; height:2.843ex;" alt="{\displaystyle U(N)}" loading="lazy"></span>, of an isolated device (self-capacitance) is twice that stored in a "connected" device in the lower limit <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle N=1}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>N</mi>
<mo>=</mo>
<mn>1</mn>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle N=1}</annotation>
</semantics>
</math></span><img src="./85982022b9eb1f295b44de55023687a490db0a39.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:6.325ex; height:2.176ex;" alt="{\displaystyle N=1}" loading="lazy"></span>. As <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle N}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>N</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle N}</annotation>
</semantics>
</math></span><img src="./f5e3890c981ae85503089652feb48b191b57aae3.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.064ex; height:2.176ex;" alt="{\displaystyle N}" loading="lazy"></span> grows large, <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle U(N)\to U}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>U</mi>
<mo stretchy="false">(</mo>
<mi>N</mi>
<mo stretchy="false">)</mo>
<mo stretchy="false">→<!-- → --></mo>
<mi>U</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle U(N)\to U}</annotation>
</semantics>
</math></span><img src="./c52cf0c8c3c8dd0bccdc7a8ed618eb8e5aae4790.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:11.052ex; height:2.843ex;" alt="{\displaystyle U(N)\to U}" loading="lazy"></span>.<sup id="cite_ref-LaFave-DCD_24-1" class="reference"><a href="#cite_note-LaFave-DCD-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> Thus, the general expression of capacitance is
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C(N)={(Ne)^{2} \over U(N)}.}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>C</mi>
<mo stretchy="false">(</mo>
<mi>N</mi>
<mo stretchy="false">)</mo>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mo stretchy="false">(</mo>
<mi>N</mi>
<mi>e</mi>
<msup>
<mo stretchy="false">)</mo>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
</mrow>
<mrow>
<mi>U</mi>
<mo stretchy="false">(</mo>
<mi>N</mi>
<mo stretchy="false">)</mo>
</mrow>
</mfrac>
</mrow>
<mo>.</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle C(N)={(Ne)^{2} \over U(N)}.}</annotation>
</semantics>
</math></span></span>
</p><p>In nanoscale devices such as quantum dots, the "capacitor" is often an isolated or partially isolated component within the device. The primary differences between nanoscale capacitors and macroscopic (conventional) capacitors are the number of excess electrons (charge carriers, or electrons, that contribute to the device's electronic behavior) and the shape and size of metallic electrodes. In nanoscale devices, <a href="Nanowires" class="mw-redirect" title="Nanowires">nanowires</a> consisting of metal atoms typically do not exhibit the same conductive properties as their macroscopic, or bulk material, counterparts.
</p>
<div class="mw-heading mw-heading2"><h2 id="Capacitance_in_electronic_and_semiconductor_devices">Capacitance in electronic and semiconductor devices</h2></div>
<p>In electronic and semiconductor devices, transient or frequency-dependent current between terminals contains both conduction and displacement components. Conduction current is related to moving charge carriers (electrons, holes, ions, etc.), while displacement current is caused by a time-varying electric field. Carrier transport is affected by electric fields and by a number of physical phenomena - such as carrier drift and diffusion, trapping, injection, contact-related effects, impact ionization, etc. As a result, device <a href="Admittance" title="Admittance">admittance</a> is frequency-dependent, and a simple electrostatic formula for capacitance <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C=q/V,}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>C</mi>
<mo>=</mo>
<mi>q</mi>
<mrow class="MJX-TeXAtom-ORD">
<mo>/</mo>
</mrow>
<mi>V</mi>
<mo>,</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle C=q/V,}</annotation>
</semantics>
</math></span><img src="./febc2618b31fcb6b4cb43cea4ad7f7439c945535.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:9.531ex; height:2.843ex;" alt="{\displaystyle C=q/V,}" loading="lazy"></span> is not applicable. A more general definition of capacitance, encompassing electrostatic formula, is:<sup id="cite_ref-LauxCapacitance_27-0" class="reference"><a href="#cite_note-LauxCapacitance-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup>
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C={\frac {\operatorname {Im} (Y(\omega ))}{\omega }},}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>C</mi>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi>Im</mi>
<mo><!-- --></mo>
<mo stretchy="false">(</mo>
<mi>Y</mi>
<mo stretchy="false">(</mo>
<mi>ω<!-- ω --></mi>
<mo stretchy="false">)</mo>
<mo stretchy="false">)</mo>
</mrow>
<mi>ω<!-- ω --></mi>
</mfrac>
</mrow>
<mo>,</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle C={\frac {\operatorname {Im} (Y(\omega ))}{\omega }},}</annotation>
</semantics>
</math></span></span>
where <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle Y(\omega )}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>Y</mi>
<mo stretchy="false">(</mo>
<mi>ω<!-- ω --></mi>
<mo stretchy="false">)</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle Y(\omega )}</annotation>
</semantics>
</math></span><img src="./f58497f00333ec38be62fdc7c4220d005bf06ad1.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:5.028ex; height:2.843ex;" alt="{\displaystyle Y(\omega )}" loading="lazy"></span> is the device admittance, and <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \omega }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>ω<!-- ω --></mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \omega }</annotation>
</semantics>
</math></span><img src="./48eff443f9de7a985bb94ca3bde20813ea737be8.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.446ex; height:1.676ex;" alt="{\displaystyle \omega }" loading="lazy"></span> is the angular frequency.
</p><p>In general, capacitance is a function of frequency. At high frequencies, capacitance approaches a constant value, equal to "geometric" capacitance, determined by the terminals' geometry and dielectric content in the device.
A paper by Steven Laux<sup id="cite_ref-LauxCapacitance_27-1" class="reference"><a href="#cite_note-LauxCapacitance-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> presents a review of numerical techniques for capacitance calculation. In particular, capacitance can be calculated by a Fourier transform of a transient current in response to a step-like voltage excitation:
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C(\omega )={\frac {1}{\Delta V}}\int _{0}^{\infty }[i(t)-i(\infty )]\cos(\omega t)dt.}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>C</mi>
<mo stretchy="false">(</mo>
<mi>ω<!-- ω --></mi>
<mo stretchy="false">)</mo>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>1</mn>
<mrow>
<mi mathvariant="normal">Δ<!-- Δ --></mi>
<mi>V</mi>
</mrow>
</mfrac>
</mrow>
<msubsup>
<mo>∫<!-- ∫ --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mn>0</mn>
</mrow>
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">∞<!-- ∞ --></mi>
</mrow>
</msubsup>
<mo stretchy="false">[</mo>
<mi>i</mi>
<mo stretchy="false">(</mo>
<mi>t</mi>
<mo stretchy="false">)</mo>
<mo>−<!-- − --></mo>
<mi>i</mi>
<mo stretchy="false">(</mo>
<mi mathvariant="normal">∞<!-- ∞ --></mi>
<mo stretchy="false">)</mo>
<mo stretchy="false">]</mo>
<mi>cos</mi>
<mo><!-- --></mo>
<mo stretchy="false">(</mo>
<mi>ω<!-- ω --></mi>
<mi>t</mi>
<mo stretchy="false">)</mo>
<mi>d</mi>
<mi>t</mi>
<mo>.</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle C(\omega )={\frac {1}{\Delta V}}\int _{0}^{\infty }[i(t)-i(\infty )]\cos(\omega t)dt.}</annotation>
</semantics>
</math></span></span>
</p>
<div class="mw-heading mw-heading2"><h2 id="Negative_capacitance_in_semiconductor_devices">Negative capacitance in semiconductor devices</h2></div>
<p>Usually, capacitance in semiconductor devices is positive. However, in some devices and under certain conditions (temperature, applied voltages, frequency, etc.), capacitance can become negative. Non-monotonic behavior of the transient current in response to a step-like excitation has been proposed as the mechanism of negative capacitance.<sup id="cite_ref-JonscherNegCap_28-0" class="reference"><a href="#cite_note-JonscherNegCap-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> Negative capacitance has been demonstrated and explored in many different types of semiconductor devices.<sup id="cite_ref-29" class="reference"><a href="#cite_note-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup>
</p>
<div class="mw-heading mw-heading2"><h2 id="Measuring_capacitance">Measuring capacitance</h2></div>
<div role="note" class="hatnote navigation-not-searchable">Main article: <a href="Capacitance_meter" title="Capacitance meter">Capacitance meter</a></div>
<p>A <a href="Capacitance_meter" title="Capacitance meter">capacitance meter</a> is a piece of <a href="Electronic_test_equipment" title="Electronic test equipment">electronic test equipment</a> used to measure capacitance, mainly of discrete <a href="Capacitor" title="Capacitor">capacitors</a>. For most purposes and in most cases the capacitor must be disconnected from <a href="Electronic_circuit" title="Electronic circuit">circuit</a>.
</p><p>Many DVMs (<a href="Voltmeter" title="Voltmeter">digital volt meters</a>) have a capacitance-measuring function. These usually operate by charging and discharging the <a href="Device_under_test" title="Device under test">capacitor under test</a> with a known <a href="Electric_current" title="Electric current">current</a> and measuring the rate of rise of the resulting <a href="Voltage" title="Voltage">voltage</a>; the slower the rate of rise, the larger the capacitance. DVMs can usually measure capacitance from <a href="Farad" title="Farad">nanofarads</a> to a few hundred microfarads, but wider ranges are not unusual. It is also possible to measure capacitance by passing a known <a href="High-frequency" class="mw-redirect" title="High-frequency">high-frequency</a> <a href="Alternating_current" title="Alternating current">alternating current</a> through the device under test and measuring the resulting <a href="Volt" title="Volt">voltage</a> across it (does not work for polarised capacitors).
</p>
<p>More sophisticated instruments use other techniques such as inserting the capacitor-under-test into a <a href="Bridge_circuit" title="Bridge circuit">bridge circuit</a>. By varying the values of the other legs in the bridge (so as to bring the bridge into balance), the value of the unknown capacitor is determined. This method of <i>indirect</i> use of measuring capacitance ensures greater precision. Through the use of <a href="Four-terminal_sensing" title="Four-terminal sensing">Kelvin connections</a> and other careful design techniques, these instruments can usually measure capacitors over a range from picofarads to farads.
</p>
<div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2></div>
<style data-mw-deduplicate="TemplateStyles:r1184024115">
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<ul><li><a href="Capacitive_displacement_sensor" title="Capacitive displacement sensor">Capacitive displacement sensor</a></li>
<li><a href="Capacity_of_a_set" title="Capacity of a set">Capacity of a set</a></li>
<li><a href="Displacement_current" title="Displacement current">Displacement current</a></li>
<li><a href="Gauss_law" class="mw-redirect" title="Gauss law">Gauss law</a></li>
<li><a href="LCR_meter" title="LCR meter">LCR meter</a></li>
<li><a href="Magnetocapacitance" title="Magnetocapacitance">Magnetocapacitance</a></li>
<li><a href="Quantum_capacitance" title="Quantum capacitance">Quantum capacitance</a></li></ul>
</div>
<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>
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<ol class="references">
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/* start https://en.wikipedia.org/ */
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<li id="cite_note-25"><span class="mw-cite-backlink"><b><a href="#cite_ref-25">^</a></b></span> <span class="reference-text"><cite id="CITEREFG._J._IafrateK._HessJ._B._KriegerM._Macucci1995" class="citation journal cs1">G. J. Iafrate; K. Hess; J. B. Krieger; M. Macucci (1995). "Capacitive nature of atomic-sized structures". <i>Phys. Rev. B</i>. <b>52</b> (15): <span class="nowrap">10737–</span>10739. <a href="Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1995PhRvB..5210737I">1995PhRvB..5210737I</a>. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1103%2Fphysrevb.52.10737">10.1103/physrevb.52.10737</a>. <a href="PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/9980157">9980157</a>.</cite></span>
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<li id="cite_note-26"><span class="mw-cite-backlink"><b><a href="#cite_ref-26">^</a></b></span> <span class="reference-text"><cite id="CITEREFT._LaFave_JrR._Tsu2008" class="citation journal cs1">T. LaFave Jr; R. Tsu (March–April 2008). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20140222131652/http://www.pagesofmind.com/FullTextPubs/La08-LaFave-2008-capacitance-a-property-of-nanoscale-materials.pdf">"Capacitance: A property of nanoscale materials based on spatial symmetry of discrete electrons"</a> <span class="cs1-format">(PDF)</span>. <i>Microelectronics Journal</i>. <b>39</b> (<span class="nowrap">3–</span>4): <span class="nowrap">617–</span>623. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2Fj.mejo.2007.07.105">10.1016/j.mejo.2007.07.105</a>. Archived from <a rel="nofollow" class="external text" href="http://www.pagesofmind.com/FullTextPubs/La08-LaFave-2008-capacitance-a-property-of-nanoscale-materials.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 22 February 2014<span class="reference-accessdate">. Retrieved <span class="nowrap">12 February</span> 2014</span>.</cite></span>
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<li id="cite_note-JonscherNegCap-28"><span class="mw-cite-backlink"><b><a href="#cite_ref-JonscherNegCap_28-0">^</a></b></span> <span class="reference-text"><cite id="CITEREFJonscher1986" class="citation journal cs1">Jonscher, A.K. (1986). "The physical origin of negative capacitance". <i>J. Chem. Soc. Faraday Trans. II</i>. <b>82</b>: <span class="nowrap">75–</span>81. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1039%2FF29868200075">10.1039/F29868200075</a>.</cite></span>
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<li id="cite_note-29"><span class="mw-cite-backlink"><b><a href="#cite_ref-29">^</a></b></span> <span class="reference-text"><cite id="CITEREFErshovLiuLiBuchanan1998" class="citation journal cs1">Ershov, M.; Liu, H.C.; Li, L.; Buchanan, M.; Wasilewski, Z.R.; Jonscher, A.K. (October 1998). "Negative capacitance effect in semiconductor devices". <i>IEEE Trans. Electron Devices</i>. <b>45</b> (10): <span class="nowrap">2196–</span>2206. <a href="ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/cond-mat/9806145">cond-mat/9806145</a></span>. <a href="Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1998ITED...45.2196E">1998ITED...45.2196E</a>. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1109%2F16.725254">10.1109/16.725254</a>. <a href="S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:204925581">204925581</a>.</cite></span>
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</ol></div>
<div class="mw-heading mw-heading2"><h2 id="Further_reading">Further reading</h2></div>
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<ul><li>Tipler, Paul (1998). <i>Physics for Scientists and Engineers: Vol. 2: Electricity and Magnetism, Light</i> (4th ed.). W. H. Freeman. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>1-57259-492-6</bdi></li>
<li>Serway, Raymond; Jewett, John (2003). <i>Physics for Scientists and Engineers</i> (6th ed.). Brooks Cole. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-534-40842-7</bdi></li>
<li>Saslow, Wayne M.(2002). <i>Electricity, Magnetism, and Light</i>. Thomson Learning. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-12-619455-6</bdi>. See Chapter 8, and especially pp. 255–259 for coefficients of potential.</li></ul>
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<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>
<ul><li><span class="noviewer" typeof="mw:File"></span> Media related to <a href="https://commons.wikimedia.org/wiki/Category:Capacitance" class="extiw external" title="commons:Category:Capacitance">Capacitance</a> at Wikimedia Commons</li></ul>
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