# Capacitance **The ability of an electrical conductor or a set of conductors to store charge and thus oppose a change in voltage across it. ** > [!infobox] Capacitance > > | | | > |:------------------------------- | ---:| > | ***Symbol*** | $C$ | > | ***SI unit*** | farad, $\text{F}$ | > | ***SI base units*** | $A^{2}\;s^{4}\;kg^{-1}\;m^{-2}$ | There are two forms of capacitance, *self* and *mutual capacitance*. In general, "capacitance" refers to mutual capacitance. Capacitance is dependent on the *geometry* of the conductors, specifically the distance between them and the surface areas opposing each other, and the *permittivity* of any material between the conductors. ## Self capacitance *Self capacitance* is the amount of electric charge required to raise the electric potential of an isolated conductor by one unit. $C=\frac{q}{V}$ Any object that is capable of being electrically charged has *self capacitance*. In self capacitance, the potential difference is measured *relative* to a reference, typically ground. ## Mutual capacitance *Mutual capacitance* is the ratio of the magnitude of electric charge held on either conductor to the potential difference between the conductors in a system of mutual capacitance. A example of a system of mutual capacitance is found in parallel-plate [[Capacitor|capacitors]]. If the charges held on the plates are $+q$ and $-q$ and the voltage between them is $V$, the capacitance is also given by $C=\frac{q}{V}$