Electric Switch

Electric switch is a device that controls the flow of electric current in a circuit. The most common type of electric switch is the snap-action toggle switch used to turn lights on and off. In such a switch, an insulated handle activates a hidden mechanism that completes or breaks the circuit. Turning the switch on connects two metal contacts so that current flows through the circuit. Turning it off separates the contacts and breaks the flow of current.

An electric switch controls the flow of electric current in a circuit. This diagram shows a light switch in the off position. Turning the switch on connects two metal contacts--colored blue above--so that current flows through the circuit.
From The World Book^™ Multimedia Encyclopedia ©1998 World Book, Inc., 525 W. Monroe, Chicago, IL 60661. All rights reserved.
World Book illustration by Zorica Dabich.

Electric switches may be classified according to the arrangement of their contacts. The simplest kind, a single pole, single throw switch, controls the flow of current along a single path. A double pole, single throw switch has two sets of contacts controlled by the same handle. In this way, two circuits can be controlled at the same time. A pair of single pole, double throw switches allows a light to be turned on and off from either of two locations. Each switch moves a contact back and forth between two wires. Electric current flows when the contacts in both switches are connected to the same wire. Flipping either of the two switches breaks the circuit by moving one contact to the other wire.

Contributor: Douglas M. Lapp, Ed.D., Director, National Science Resources Center, National Academy of Sciences/Smithsonian Institution.

Electric Switch

Master Index