What is a relay?

• A. A device that stores electrical energy
• B. A grounding strap
• C. An electrically operated switch
• D. A manual switch

Answer: (C)

Relays are electrically operated switches. They use a coil that, when energized, creates a magnetic field that pulls a contact to open or close the high‑current circuit. This lets a small control current switch a much larger current on another circuit, while keeping the control and power sides electrically separate. In cars, relays let a dash switch or electronic control energize things like headlights or the fuel pump without passing a large current through the control wiring. Relays can be normally open (the circuit is off until the coil is energized) or normally closed (the circuit is on until energized). The other options describe energy storage devices, grounding conductors, or a manual switch, none of which perform the electromagnetically controlled switching function of a relay.