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Why Can We Experience An Electric Shock From Neutral

  1. Dec 3, 2011 #1
    I have always been under the impression that the "Live" conductor was the most dangerous conductor.

    The Live carries 120V (US) 240V (UK) and the Neutral carries 0V, but yet it is still possible to get an electric shock from a Neutral :confused:

    Why is this possible?

    Is it because it is Alternating Current and the direction of the current changes?

    If so, would it be fair to say that in an DC circuit, it wont be possible to get shock from a Negative conductor?

    Thanks in advance

    Nathan
     
  2. jcsd
  3. Dec 3, 2011 #2
    Voltage is always relative to something - not an absolute quantity.

    The "Neutral is 0V" is only 0V relative to ground. Relative to the Hot, it's 120V/240V.

    The reason the "to ground" matters is that you can shield the appliance or device by grounding it explicitly and then as a human resistor, anything you are likely to touch that is connected to the Neutral will result in zero current flowing through you. Then it's only a matter of worrying about the hot wire, and that current preferentially flow to any chassis grounded metal rather than through you.
     
  4. Dec 3, 2011 #3
    You talking about static shock? It can happen because YOU are charged up!!!!:rofl:
     
  5. Dec 4, 2011 #4
    Thanks alot
     
  6. Dec 4, 2011 #5
    Assumptions:
    1. US standard residential electrical system. Also true in Canada. I don't know about Brits.

    2. By getting shocked from the neutral, you mean that you are touching the neutral conductor and some other grounded conductive surface (like bare feet on a concrete floor) and get somewhere between a sharp tingle and internal bright flashing lights, followed by "EEEEYWOOOOO"

    3. You are not discussing swimming pools and voltage drop on the utility neutral from the subatation.

    The Neutral is susposed to be bonded to the grounding conductor only in one place - at the first disconnect after the utility transformer. Generally this is at the main panel. The grounding conductor is susposed to have a medium decent connection to earth. The only difference of potential between the grounding conductor (also earth) and the neutral is the voltage drop along the neutral conductor of a loaded circuit. As most this would be about 3V. And it is really hard to feel 3 volts (but is is possible to get a bit of a tingle)

    So, if you are getting shocked by the neutral then something in the electrical system is broken. And the broken part is likely in the neutral conductor - between the place you are touching and the main panel. With a break in the neutral, the neutral will rise to 120V with respect to earth.

    Another possibility: How are you identifying the neutral? By it being colored white? If so, some parts of normal, correct, residential installations will have white wires that are energized.

    Now that we got by that, may I gently suggest:
    Don't be touching electrical wires until after you have verified (with a known good meter) the circuit is dead. Sweaty fingers, sweaty feet, damp shoes, concrete floor, indiscriminate touching of 120V residential electrical has a bit better than even money chance of not killing you. Although when you tie into an energized wire, you may feel that it is killing you.

    ice
     
  7. Dec 4, 2011 #6
    It really doesn't matter much AC or DC. It depends mostly on voltage and skin resistance. As for DC, grounded or ungrounded system?

    An clean un-grounded DC system won't have a potential to earth. But all it takes a bit of dirt on one side of the source (battery) and the other side can get elevated above earth to source potential.

    I get leery of sticking my bare hands into ungrounded DC systems above 48V. 125DCV passing hand to hand hurts - even with dry hands.

    ice
     
  8. Dec 4, 2011 #7
    I completely agree with iceworm..... especially if you are identifying the neutral wire by insulation colour.
    In domestic lighting circuits especially you may find that the neutral colour wire is a live wire used to connect switches.
     
  9. Dec 4, 2011 #8

    davenn

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    Gold Member

    We must also remember that this is an international forum and that colour codes vary from country to country. Before commenting on specific colour codes to a given OP's question, we should make sure we know where they reside so as not to give misleading info :)

    USA -- Black = hot; White = neutral; what do you use for earth ?
    UK -- I have no idea
    NZ and Australia -- Brown = hot; Blue = neutral and green/yellow striped = earth

    Dave
     
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