The top two pins of the 3-pin power plug are the live and neutral pins. The live pin feeds power into an appliance while the neutral pin draws unused power back to the power source, creating a closed circuit for power to flow through. The ground pin acts as a safety device that is usually connected to the metal casing of an appliance. If the appliance malfunctions and the metal casing becomes electrified, the ground pin will direct the voltage into a safe ground so that the appliance user is not electrocuted. If a large current flows through the live wire initially then the fuse will blow, thus cutting of the circuit and preventing a possible fire.