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Does AC current have direction? And how can I find the live wire (household plug)?

  1. Jul 25, 2009 #1
    How can I find the "live" wire (household plug)?

    After playing with an electrical socket (with caution), I realized there is 120v between the black and ground wires. However, the white is supposed to be "live", black is "neutral", and copper is "ground". Since there is 120v between black and ground, and between black and white, it makes me conclude that the wires were not properly wired, and that the black in my cause is actually "live", while the white is "neutral".

    As such, is there a definite way of finding which is "live" and which is "neutral"?
    Last edited: Jul 25, 2009
  2. jcsd
  3. Jul 25, 2009 #2


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    Staff: Mentor

    Last edited by a moderator: Apr 24, 2017
  4. Jul 26, 2009 #3


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    Re: Does AC current have direction? And how can I find the "live" wire (household plu

    If you have a live outlet, and a multimeter, you can contact the ground with one probe, then reference that to either slot. The slot with 120v relative to the ground is your live contact and the other slot (0V to ground) is neutral. For US applications, the longer slot should be neutral and the shorter slot should be hot. With the ground opening at the bottom, the longer neutral slot is at the right and the hot is at the left.
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