An electric short or short circuit can occur when two wires which are supposed to be separated come into contact, perhaps through loose connections in a socket or worn out insulation. A screwdriver inserted into a socket can also cause a short circuit and severe injury to the person holding it.
Ordinarily the circuit followed by an electric current forces it to overcome certain resistances by generating energy which which heats an electric toaster or lights an electric lamp. But when the two sides of an electric circuit are accidentally connected by a path which cuts out this resistance, a short circuit occurs, because electric current always flows through the path of least resistance.
When this happens the current flow becomes so high that it melts the piece of wire or fuse inserted in the circuit as a safety measure and so cuts off the voltage. Damage to an appliance is thereby avoided, for if the excess current continued to flow, it would cause the appliance to become very hot.