When an electrical device is plugged into an outlet, it completes an electrical circuit that powers the device. If anything causes the circuit to become imbalanced—that is, the plugged-in device conducts more electricity than it needs—it can put the device’s user at risk of electric shock, unless it is plugged into a ground fault circuit interrupter.
What does a ground fault circuit interrupter do?
Ground faults can occur when electricity finds a path between its current to a conductive surface. This can cause burns, shocks, electrocutions, and fires.
A ground fault circuit interrupter, or GFCI, is a device that detects the potential for ground faults based on circuit imbalances: if the “outgoing” current—the current traveling from the outlet to the connected device—outweighs the “incoming” current—the current returning to the outlet—by 5 milliamperes or more, the GFCI will immediately break the circuit.