Capacitance

Common symbols	C
SI unit	farad
Other units	μF, nF, pF
In SI base units	F = A2 s4 kg−1 m−2
Derivations from other quantities	C = charge / voltage
Dimension	${\displaystyle {\mathsf {L}}^{-2}{\mathsf {M}}^{-1}{\mathsf {T}}^{4}{\mathsf {I}}^{2}}$

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Capacitance is the ability of a material object or device to store electric charge. It is measured by the charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized are two closely related notions of capacitance: self capacitance and mutual capacitance.^{[1]: 237–238} 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 capacitor, an elementary linear electronic component designed to add capacitance to an electric circuit.

The capacitance between two conductors depends only on the geometry; the opposing surface area of the conductors and the distance between them; and the permittivity of any dielectric 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.

The SI unit of capacitance is the farad (symbol: F), named after the English physicist Michael Faraday.^[2] A 1 farad capacitor, when charged with 1 coulomb of electrical charge, has a potential difference of 1 volt between its plates.^[3] The reciprocal of capacitance is called elastance.

Historically: the farad was regarded as an inconveniently large unit and the range of capacitors encountered would range from a few picofarads to a few thousand microfarads.^[4] More recent developments in dielectric materials has permitted the manufacture of many types of capacitor of up to (as of 2024^[update]) a few thousand farads in reasonable physical sizes.^[5] These are usually described as 'supercapacitors'.