What is a primary use of a capacitor in electrical circuits?

A capacitor's primary function in electrical circuits is to store and release electrical energy, making it integral to a wide range of applications. When a voltage is applied across a capacitor, it accumulates charge on its plates, storing electrical energy in an electric field. This stored energy can be released when necessary, allowing it to smooth out fluctuations in electrical supply, filter signals, or provide quick bursts of energy in various electronic applications.

For instance, in power supply circuits, capacitors help maintain steady voltage levels by discharging their stored energy when there are sudden demands. In audio circuits, they are used to filter out unwanted noise by allowing certain frequencies to pass while blocking others. This ability to both store and later discharge energy makes capacitors versatile components in both AC and DC circuits, facilitating various functions without altering energy form as indicated in other options.