Switches are used to open and close an electric circuit, giving us control over the flow of current. For instance, electrical machines or appliances are usually kept plugged into an electrical source, but have switches that turn the appliances on or off.

A closed switch means a closed circuit which means “on.” When the switch is closed, the circuit is closed and electricity flows freely through the wires in the circuit and the appliance operates using the electrical current. An open switch means an open circuit which means “off”. When the switch is open, or off, the circuit is open and no electricity flows through the circuit so the appliance has no energy with which to do its work.