Appliances have three safety devices: the fuse; the earth wire and the switch. These devices are designed to stop you from being electrocuted and to prevent the appliance from being damaged. A fuse is a thin piece of wire which will melt when too much current passes through it. The fuse stops a large current from flowing through the appliance which could cause wires to overheat, melt or catch fire. Together, the fuse and switch control the amount of electricity that enters an appliance. To prevent electrocution, the earth wire is connected to the casing of the appliance.