What is the function of a relay in electrical systems?

The function of a relay in electrical systems is to control the flow of electricity. A relay is an electromechanical switch that operates by using an electromagnetic field to open or close contacts and control a circuit. Relays enable a low-power signal to switch a higher power circuit on or off, providing isolation between the control and the load circuits. This allows for controlling devices that operate on high voltages or currents with a safe and lower voltage control signal.

In various applications, including automotive, industrial, and home automation, relays enable control over the operation of motors, lights, and other equipment using a minimal input from a control source. This capability is essential for tasks such as safety interlocks, remote operation, and automation of systems where manual control is impractical.

The other options involve functions that are unrelated to the mechanism and purpose of a relay. Converting AC power to DC power pertains to rectification, storing electrical energy relates to capacitors or batteries, and measuring resistance is a task typically performed by multimeters or ohmmeters, not relays.