What is the function of a capacitor in an electrical circuit?

The function of a capacitor in an electrical circuit is to store and release electrical energy. Capacitors are passive components designed to accumulate charge when connected to a voltage source and then release that stored energy when needed. This ability to store electrical energy makes capacitors essential in various applications, such as smoothing out voltage fluctuations in power supplies, filtering noise in electronic circuits, and timing applications where they control the rate at which a voltage rises or falls.

In contrast, while some components in circuits may regulate voltage, convert AC to DC, or amplify signals, these functions are typically handled by voltage regulators, rectifiers, and amplifiers, respectively, and not by capacitors. Thus, the primary and defining role of a capacitor is its capability to store and release electrical energy, which is why this choice stands out as the correct answer.