Which device interrupts a circuit when a fault current to earth is detected?

• A. AFCI
• B. Surge protector
• C. Ground fault circuit interrupter (GFCI)
• D. OCPD

Answer: (C)

The device is designed to protect people by sensing when current leaks to earth and then breaking the circuit quickly. A ground fault circuit interrupter (GFCI) does just that: it monitors the current flowing in the hot and neutral conductors and looks for any difference. If some current escapes to ground—such as through a person touching a live conductor or through moisture—the currents no longer balance, and the GFCI trips, cutting off power in a fraction of a second. This rapid disconnection minimizes the risk of electric shock.

Surge protectors, by contrast, respond to voltage spikes to protect equipment; they don’t reliably detect or interrupt fault currents to earth. AFCIs target arcing faults to reduce fire risk but aren’t specialized for ground-leakage protection. Overcurrent protective devices (OCPDs) are concerned with excessive current from overloads or short circuits, and while they can trip on faults, they aren’t specifically designed to detect small leaks to ground like a GFCI is.