An electric switch is an electrical component that breaks or closes an electric circuit. Opening the switch (breaking the circuit) means turning off the electrical device and closing the switch (completing the circuit) allows an electrical current to flow so that the device is on.
Switches should be placed on the hot line so that when they've turned off the electrical device (like a lamp) it is at the same voltage as the ground. This is to reduce the risk of electric shock.
The University of Colorado has graciously allowed us to use the following Phet simulation. This simulation explores how switches work in an electric circuit:
For Further Reading
For further information please see the related pages below: