Capacitors

Capacitors are a passive electrical component with two terminals that store electromagnetic energy in the form of an electric field. Terminals are connected to two conductive plates that have a dielectric material between them. The capacitor stores electric charge on its conductive plates. The charged plates separated by the dielectric create an electric field.

Capacitors are classified based on physical materials used for three-layer conductor-dielectric-conductor structure. For example, capacitors with metal-dielectric-electrolyte materials are called electrolytic capacitors; metal-ceramic-metal capacitors are called ceramic capacitors, etc.

Capacitance is a parameter of a capacitor that indicates the amount of stored electric charge for a given voltage applied to its terminals. It is measured in farads (F). For example, doubling the capacitance will double stored electric charge (for a given constant voltage at terminals).

The maximum operating voltage of a capacitor indicates the voltage that should not be exceeded during its usage. Non-polarized capacitors may be connected either to positive or negative voltage. Polarized capacitors must be connected to a positive voltage, with the positive terminal being marked on the packaging.

Current flow through a capacitor causes heating due to the equivalent series resistance (ESR) of the capacitor. In order to avoid overheating, some capacitors are rated with the maximum allowed current.