The capacitance C of a capacitor is defined as the ratio of the maximum charge Q that can be stored in a capacitor to the applied voltage V across its plates. In other words, capacitance is the largest amount of charge per volt that can be stored on the device: C = Q V
KEY POINT - The capacitance of a capacitor, C, is defined as: Where Q is the charge stored when the voltage across the capacitor is V. Capacitance is measured in farads (F). 1 farad is the capacitance of a capacitor that stores 1 C of charge when the p.d. across it is 1 V.
When a voltage V is applied to the capacitor, it stores a charge Q, as shown. We can see how its capacitance may depend on A and d by considering characteristics of the Coulomb force. We know that force between the charges increases with charge values and decreases with the distance between them.
When capacitors in series are connected to a voltage supply: because the applied potential difference is shared by the capacitors, the total charge stored is less than the charge that would be stored by any one of the capacitors connected individually to the voltage supply. The effect of adding capacitors in series is to reduce the capacitance.
The Capacitance is determined by, among other things, the characteristics of the dielectric material. International standards speak of the Dielectric Constant or permittivity, designated by the symbol ε. A capacitor serves as a reservoir for electric charges.
When a capacitor is charged, the amount of charge stored depends on: its capacitance: i.e. the greater the capacitance, the more charge is stored at a given voltage. KEY POINT - The capacitance of a capacitor, C, is defined as: