A switch is a device which can close and open an electric circuit. A switch should always be connected on the live-wire side, so that when the switch is off, the element or bulb is neutral. Then it is quite safe for a person to inspect it in case of a fault If, on the other hand, the switch is on the neutral side, the element will remain live when the switch is off. The will remain live when the switch is off. The person touching it is likely to get a severe shock. You should take care not to touch a switch with wet hands, as water is a good conductor of electricity. If there is a leakage from the live terminal, you may get a severe shock as the current flows through your body to be earth.