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Short circuiting : If due to defective or damaged wiring, the live and neutral wires come in direct contact, the resistance of the circuit becomes almost zero and an extremely large current flows through the circuit. This is called short circuiting. It results in heating the line wires and may damage the appliance. It may produce spark at the place of short circuit and cause fire. Short circuiting can be prevented by using an electric fuse in live wire.

Overloading: When a large number of high power appliances are switched on simultaneously, they draw extremely large current from the mains. If the current drawn from the mains exceeds the safety limit (5 A for domestic line and 15 A for power line), then this is known as over loading. As a result of overloading, the wires get over heated and the appliances may get damaged. This can be avoided by using an electric fuse in live wire.