What’s happening behind the scenes when we flick on and off a light switch? There are two screws attached to the switch; one’s a live wire and the other delivers the power to light. When we hit the light switch we’re breaking the hot wire (that’s the one that delivers the power) from the fuse power. Essentially all we’re doing is making a connection; like if we were holding two fingers apart and then allowing them to touch. When they touch that connection allows power to go through and the light turns on.