What type of circuit component uses an electromagnet to function?

A relay is a type of circuit component that utilizes an electromagnet to operate. When an electric current flows through the coil of the relay, it generates a magnetic field that activates the electromagnet. This action causes a switch to close or open, allowing the relay to control the flow of electricity in a different part of the circuit.

Relays are commonly used to control high voltage circuits with low voltage signals, providing isolation and enabling automation in various electrical systems. They can be found in applications such as automotive systems, industrial machinery, and home automation, where they facilitate the conversion of a small input signal into a larger output action.

The other options, such as capacitors, resistors, and transistors, perform different functions in electronic circuits and do not operate through an electromagnet. Capacitors store energy in an electric field, resistors limit current flow, and transistors act as switches or amplifiers, but none use the principle of an electromagnet to function like a relay does.