What is the primary function of a capacitor?

The primary function of a capacitor is to store electrical energy in an electric field. This capability arises from its fundamental structure, which consists of two conductive plates separated by an insulating material, or dielectric. When a voltage is applied across the plates, an electric field is created, allowing the capacitor to accumulate and hold electrical energy.

Capacitors are widely used in various electronic applications, including filtering, coupling, and timing circuits. Their ability to release the stored energy when needed makes them essential components in smoothing out voltage fluctuations in power supplies or providing bursts of current in signal processing.

In contrast, the other options focus on functions not inherent to capacitors. While resistors are designed to resist the flow of current, a capacitor allows current to flow in a controlled manner according to the voltage across it. Measurement of voltage levels typically involves using devices like voltmeters rather than capacitors. Lastly, converting energy from alternating current (AC) to direct current (DC) is primarily handled by rectifiers, not capacitors, although capacitors can play a supporting role in smoothing the output after conversion.