How does a ground-fault circuit interrupter operate?

A ground-fault circuit interrupter (GFCI) operates by monitoring current imbalances in conductors. This device is specifically designed to protect against electric shock caused by ground faults, which occur when electricity leaks from the intended circuit to the ground.

The GFCI constantly compares the input current flowing to the device with the output current returning from it. Under normal conditions, these two currents should be equal. If there is a discrepancy, indicating that some current is leaking (a ground fault), the GFCI will quickly shut off power to the circuit. This rapid response—often within milliseconds—helps prevent serious injury or death due to electric shock.

The other methods mentioned, such as measuring voltage fluctuations, detecting temperature changes, or analyzing circuit continuity, do not specifically address the reason or method for a GFCI's operation. A GFCI focuses solely on current imbalances to ensure safety, making the option regarding current monitoring the most accurate representation of its function.