What is the function of a relay in electrical circuits?

A relay serves the critical function of acting as a switch in electrical circuits. It allows one circuit to control another circuit without a direct electrical connection between them. This is achieved using an electromagnetic mechanism, which enables the relay to open or close contacts based on the presence or absence of an electrical signal in the control circuit.

When a voltage is applied to the relay coil, it generates a magnetic field that moves an armature, either closing the contacts to complete the circuit, or opening them to break the circuit. This enables the relay to control high-power devices with low-power signals, providing both flexibility and safety in electrical systems. Essentially, relays are key components in automation, allowing for remote operation and control of electrical systems, which is particularly useful in applications where switching must be done safely and efficiently.

The other options do not accurately describe the primary function of a relay. While it may indirectly contribute to protecting against overload or measuring current through auxiliary functions, its primary role is as a switch that helps control electrical devices and circuits.