ground wire provides a conducting path to the earth which is independent of the normal current-carrying path in an electrical appliance. As a practical matter in household electric circuits, it is connected to the electrical neutral at the service panel to gaurantee a low enough resistance path to trip the circuit breaker in case of an electrical fault (see illustration below). Attached to the case of an appliance, it holds the voltage of the case at ground potential (usually taken as the zero of voltage). This protects against electric shock. The ground wire and a fuse or breaker are the standard safety devices used with standard electric circuits.