A capacitor is a device that stores electrical charge between two conducting plates separated by an insulating material. The capacitance of a capacitor determines how much charge it can store and is measured in Farads. For capacitors in parallel, the total capacitance is the sum of the individual capacitances. For capacitors in series, the reciprocal of the total capacitance is the sum of the reciprocals of the individual capacitances. When a capacitor is charged, it stores electrical potential energy equal to 1/2 CV^2, with half the energy used to charge it dissipated as heat.

1. Capacitors

4. Capacitors in Parallel We put 3 capacitors with capacitances C 1 , C 2 and C 3 in parallel V Q 1 Q 2 Q 3 C 1 C 2 C 3 Charges on individual capacitors: Q 1 = C 1 V Q 2 = C 2 V Q 3 = C 3 V

7. Capacitors in Series V C 1 C 2 C 3 V 1 V 2 V 3 Q Individual charges are equal. Why?

11. Graph of Q against V 0 V Q