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Posted by Erik Dillenkofer on September 20, 2007, 5:21 am
Think of it this way. The receptacle is acting as an open point between the
black and the neutral. If the neutral is open at another point and a lamp is
plugged into the receptacle, the lamp closes the open point in between the
black and the neutral at the receptacle, and the neutral has just become an
extension of the black up to the open point. That's why he measures 120V. If
the open point was connected like it should have been, the current would
return to the ground at the panel and he'd measure zero volts between
neutral and ground.
>
>> Any residential circuit on which has power drawn from the hot needs a
>> neutral. The neutral carries the current to earth ground.
>
> Actually, it returns it to the source, the power company
> transformer--the earth ground is relevant only because the local
> transformer is center tapped and earthed.
>
>> The difference/potential in those conditions is the neutral will be
>> at a potential equivalent to the difference voltage drop of the the
>> load and the actual supply voltage AND earth ground. Thus, the
>> neutral is hot minus the load vs. earth ground is the actual
>> potential.
>
> Not sure what you are saying here. If the circuit consists of Hot
> Transformer terminal -> Hot wires -> Load -> Neutral wires -> Grounded
> Transformer terminal, then the voltages above ground at each point
> might be 120V (Transformer), 119V (Hot wire at the Load), 1V (Neutral
> wire at the Load), 0V (Grounded Transformer terminal). Under normal
> operation, there will never be a 120V voltage difference between a
> neutral and an earth (ground).
>
> As for the spark, it indicates current flow and was probably just due
> to completing the circuit by connecting the neutral to the EGC, which
> is bonded to the grounded service conductor at the main disconnect.
>
> Cheers, Wayne
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