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Charge flow through a mains tester

  1. Oct 4, 2010 #1
    We often use screw driver testers, where we touch one end of the screw driver with our finger and put the pointed end into the mains. The bulb inside the tester glows, indicating that the mains are active.
    My question is, how is the circuit completed in this case? If charge flows from our body to ground, how does it go back to the 'source', which is the other pin of the mains power supply?
     
  2. jcsd
  3. Oct 4, 2010 #2

    dlgoff

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    The "other pin of the mains" is at ground potential. So you have a path; for very low current in this case.
     
  4. Oct 4, 2010 #3
    Does that mean that both the neutral and earth pin are shorted i.e. connected to the ground?
     
  5. Oct 4, 2010 #4

    dlgoff

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    Residential wiring in the US requires a safety ground alone with the neutral which are both attached to ground at the breaker box.
     
  6. Oct 5, 2010 #5

    MATLABdude

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    I've got one of these in my tool bag (a non-contact voltage detector):
    http://www.mygreenlee.com/GreenleeD...=showGreenleeProductTemplate&upc_number=09022

    It's able to pick up the 'hot' leg of household AC without a return path or even any (significant) current flowing through the wire. May seem magical (and may have literally been a life-saver once or twice) but it just picks up the 50/60 Hz radiating off the cabling. There's a more expensive model which allows you to adjust the sensitivity and trace live wiring inside of walls / ceilings, but tone and probe kits work a little better for that (the toner injects a stronger and higher frequency signal that's more easily detected by the probe--but it's still the same basic principle)
     
  7. Oct 5, 2010 #6
    That means in the case of a charger, charges flow from the 'phase' pin of the socket to human body and then from the common ground to the neutral part of the socket, since neutral and earthing are connected. Is this explanation correct?
     
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