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How an Electric Light Switch Works

Light switches are simple in design. Current flows through a switch to the load, such as a ceiling light. When you flip the switch off, it breaks the circuit and interrupts the flow of electricity. A light switch has two terminals and sometimes a ground terminal. The hot wire from the power source is connected to one of the terminals. The hot wire going to the load (such as a light) is connected to the second terminal.

Caution: Please read our safety information before attempting any testing or repairs. References to existing wiring assume that it is properly wired, which may not be the case in your home.

Which Wires Get Connected to the Switch?

There is a safe and correct way to wire a switch. Some people have wondered, what difference does it make, which wire gets connected, the hot or the neutral wire will both break the circuit if connected to the switch. While that is true, what it doesn't consider is that if you interrupt the hot wire at the switch - the light socket, outlet or whatever will not be energized. However, if you were to interrupt the neutral wire at the switch, then the hot wire runs the other way, through the load (the light, outlet or whatever), all the way to the light switch where the circuit is broken by the switch. What is the difference you ask? If you stick your finger into a light socket on a circuit that is neutral switched, electricity is able to travel to the light socket, through you to ground and you would thus be shocked. By interrupting the hot wire at the switch instead of the neutral in a properly wired circuit, you have stopped the current before it passes through the load.

How Do I Know if I Need to Replace a Light Switch?

When a light switch fails, symptoms include a loose or wobbly switch or it may be stiff or difficult to switch. Lights that flicker may indicate a switch that is shorting. A switch that has failed completely will fail to turn on or in rare cases fail to turn off a circuit.

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