What is the primary function of a relay?

The primary function of a relay is to mechanically switch electrical circuits on or off. A relay is an electromechanical device that uses an electromagnetic coil to open or close contacts in a circuit, allowing it to control a higher power circuit with a lower power signal. This characteristic makes relays useful for controlling devices such as motors, lights, and other equipment from a distance, facilitating automation in various applications.

The design of a relay allows for isolation between the control circuit and the circuits being powered, enhancing safety and reliability in electrical systems. In essence, the relay acts as a switch that can be activated by an electrical signal, enabling the control of larger currents without direct human intervention. This feature is critical in many electrical and automation systems, making relays indispensable components in industries ranging from manufacturing to automotive.

Other choices focus on monitoring electrical current, measuring voltage levels, and protecting against overload, which represent different functions or devices rather than the primary role of a relay in electrical circuits.