Which device serves as a low-current control to energize a high-current circuit?

• A. Fuse.
• B. Circuit breaker.
• C. Relay.
• D. Ignition switch.

Answer: (C)

Relays are used to switch a high-current circuit using a separate, low-current control signal. An automotive-style relay has a small coil that draws little current; when that coil is energized, it creates a magnetic field that pulls contacts together and completes the high-current path. This lets a low-current switch or control circuit safely energize motors, lights, or other heavy loads without running heavy current through the control wiring.

Fuses and circuit breakers are protective devices that interrupt current to prevent damage or fire; they don’t provide a controlled high-current path from a low-current control signal. An ignition switch is a manual control that directly connects or disconnects circuits in the ignition and may handle significant current, but it isn’t designed to energize a separate high-current circuit via a low-current control signal in the way a relay does.