What is a GFCI and where is it used?

A GFCI (ground fault circuit interrupter) is used to detect higher-than normal-ground leakage current and turn off the circuit once it does. Under the NEC (National Electrical Code), GFCI protection of AC sockets near earth ground, bathtubs or showers is mandatory. By detecting the current through a person’s body into the ground and then turning off the AC circuit, GFCI can prevent electrocution when a person accidentally comes in contact with a live AC source.