Which safety device is primarily used to prevent electrical shock?

The ground fault circuit interrupter (GFCI) is designed specifically to prevent electrical shock by quickly shutting off power when it detects an imbalance in the electrical current. This imbalance can occur when there is a fault, such as a short circuit or if a person inadvertently touches a live wire, allowing electrical current to flow through their body. The GFCI monitors the incoming and outgoing current, and if it senses that the outgoing current is not equal to the incoming current (indicating a possible leak), it will trip and cut off the electrical supply almost instantaneously. This quick response significantly reduces the risk of serious injury or fatality from electrical shock.

Other devices mentioned, while important for overall electrical safety, serve different functions. For example, a fuse helps to protect electrical circuits from overloads by breaking the circuit when excessive current flows, but it does not specifically target ground faults that pose a risk of shock. A surge protector is designed to protect equipment from voltage spikes, and an electrical isolator is used to disconnect equipment from a power source for maintenance, neither of which directly prevents electrical shock in the same manner as a GFCI does.