Switches are used to control power to a load. They can be found on anything that runs on electricity. They can be used to control power to garbage disposals, exhaust fans, ceiling fans, gas fireplaces, receptacles, appliances and electronics.
When a switch is off (open), the circuit path is open and no current flows through a circuit. When a switch is on (closed) a continuous path is created to allow current to flow through the circuit and energize the load.
Single Pole Switch
A single pole switch is the most common type of switch. It has two terminals and it is either open or closed. A switch must be connected to the line side of a load and not the neutral. If a switch is connected to the neutral side of a light bulb (or other load) the bulb will always be connected to the line even when the switch is turned off.