WHAT IS A GROUND FAULT CIRCUIT INTERRUPTER?
These special electrical devices (GFCI’s) shut the power off to a circuit when as little as .005 amp is leaking. Under normal circumstances, the current flowing through a circuit is the same at any point. That is, if there is a 5 amp flowing through the white wire coming back.
If there is a flaw in the system, some electricity may be flowing to a dangerous spot, but there may not be enough flowing to blow a fuse or trip a breaker. For example, if the electrical insulation in an appliance is defective, there may be a small current leaking to the case of the appliance.