Every modern home has several switches in every room to stop and start the flow of electricity. Just think how troublesome life would be without them. If we had no switches, we would have to either keep our radios, TVs, stereos, and lights on all the time, or pull the plug from the socket whenever we wanted them off and insert it to start them up again.
What a switch does is stop and start the movement of electric current, which is continuously flowing into our homes. The most common kind of switch used in homes is called the knife switch, because of its knifelike handle and blade.
Wire contacts in the walls have current going in one contact and out the other. When a light switch is in the ON position, the blade is down, keeping the contacts together and permitting electricity to flow directly from the electric company generator through your house wires into the bulb socket and into the bulb itself.
Then, when you turn the switch to the OFF position, you are lifting the blade and thus breaking the contacts and stopping the electric current that powers the light.
The average light bulb can last for 750 to 1,000 hours!