Explanation: A capacitor (originally known as condenser) is a passive two-terminal electrical component used to store energy in an electric field. Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass, in filter networks, for smoothing the output of power supplies, in the resonant circuits that tune radios to particular frequencies, in electric power transmission systems for stabilizing voltage and power flow, and for many other purposes. The capacitance is greatest when there is a narrow separation between large areas of conductor; hence capacitor conductors are often called plates, referring to an early means of construction.