What is the purpose of a GFCI?

• A. To regulate voltage
• B. To protect from short circuits by blowing a fuse
• C. To quickly cut off power if a ground fault is detected
• D. To limit current to a safe level

Answer: (C)

GFCIs protect people from electric shock by detecting ground faults and quickly interrupting the circuit. They watch the current in the hot conductor and compare it to the current returning on the neutral. If some current leaks to ground—such as through a person or wet surrounding—the imbalance triggers the device to trip, cutting power in a fraction of a second. This protection threshold is very small (about 4 to 6 milliamps), allowing rapid response to leakages that could be dangerous. This function is distinct from regulating voltage or blowing a fuse to stop a short circuit; it’s specifically about stopping shock hazards caused by ground faults, which is why GFCIs are essential in wet areas like bathrooms, kitchens, and outdoor outlets.