An earth wire, or ground wire, contains the charging reservoir on a circuit and provides a connection with the earth. The earth wire protects people from electrical shock by providing the current with a fast route to the earth, which allows the current to bypass an electrical short or other problem.
Along with fuse breakers, earth wires provide the primary source of safety in electrical systems. The earth wire is not required to operate the circuit, but if it is removed or damaged, the person handling the wires risks suffering an electrical shock. Additionally, electrical fires are far more common if no earth wire is used on the circuit.