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I have an older light switch, with just 2 wires. One is energized, the other is not. So, I assume the later just brings energy to the light when switch is on. However, using a multimeter, if I test them, I get 120 v. I was not expecting it, because if the second wire goes to the hot side of the light, they should not form a circuit and give 120 v. Am I correct? It's not possible that one is hot and one is neutral, otherwise it would be a short circuit when switching to on, correct? Thank you for any help!

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What you describe is normal.

When you close the switch you complete the circuit and the voltage across the switch will drop to zero.

With the switch open, there is no current flowing but the wire to the light is connected through the light to neutral. You are measuring the difference between neutral and hot (live)

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If the switch powered an old fashioned incandescent light bulb and you took the light bulb out you would get zero volts reading across the switch.

With a good lightbulb installed, the meter doesn’t allow enough current to pass to light the lightbulb, but the lightbulb completes the circuit so you see 120v on your meter.

If the switch is still installed, and you turn it on so that the lightbulb is lit, reading voltage across the switch will give a zero volt reading.

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