What device is a fast-acting circuit breaker that senses small imbalances in a circuit and interrupts power to prevent shocks?

• A. Ground Fault Circuit Interrupter (GFCI)
• B. Circuit Breaker
• C. Fuse
• D. Surge Protector

Answer: (A)

Protection against electric shock is achieved by a ground fault interrupter that continuously compares the current in the hot and neutral conductors. When a fault causes some current to leak to ground, an imbalance appears, and the device trips quickly to cut power. This fast-acting response typically occurs at leak levels around 4–6 milliamps and takes only a fraction of a second, preventing the person from receiving a dangerous shock. GFCIs can be installed as outlets or as circuit-breaker protection in a panel. The other devices have different purposes: a circuit breaker protects against overcurrent or short circuits; a fuse also interrupts due to overcurrent but is single-use; a surge protector guards against voltage spikes and does not detect or interrupt leakage currents.