What is a capacitor primarily defined as?

A capacitor is defined primarily as a component formed when two conductive materials, typically metals, are separated by an insulating material known as a dielectric. This configuration allows the capacitor to store electrical energy in the form of an electric field when a voltage is applied across its terminals. The capacitor’s ability to store charge is what distinguishes it from other passive electrical components like resistors and inductors.

In practice, when a voltage is applied, positive and negative charges accumulate on the conductive plates of the capacitor. The amount of charge that a capacitor can store is directly related to the surface area of the plates, the distance between them, and the properties of the dielectric material. This fundamental characteristic makes capacitors essential in a wide variety of electronic circuits for purposes such as energy storage, filtering, and timing applications.

The other options describe components or devices that do not accurately represent the primary function or definition of a capacitor. For instance, while a device that increases voltage is associated more with transformers or voltage boosters, a resistor's primary role is to limit current rather than to store energy, and devices converting electrical energy into mechanical energy refer to motors or actuators. Hence, the correct definition focuses on the structural and functional aspects of a capacitor as a device that stores energy through an