On 9/16/2011 11:02 PM, John Gilmer wrote:


Consider two simple circuits, A and B, each supplying no loads other
than a single 100W light bulb, each of which is turned on -- but,
unbeknowst to you, their neutrals are cross-connected. Well and good.
Now suppose you need to replace the fixture on circuit A. Knowing that
it's on circuit A, you shut off that breaker, and disconnect the hot
lead to the fixture. Now when you go to disconnect the neutral lead, you
get a shock, because -- and I think this is the point you are missing --
electricity doesn't "follow the path of least resistance" as many people
believe, it follows *all possible paths*, including the one that you've
just made with your body by touching that energized lead.

Huh?

The reason you don't use the "wrong" neutral is just the subtle effect
of poor cancellation of the magnetic field generated by current carrying
conductors. If the conductor and it's neutral are close to each other
their magnetic fields cancel.

I know that. But that's completely unrelated to the shock danger.

You *can* get shocked by the neutral.

The main time neutrals can produce a dangerous situation is when,
somehow, they get dis-connected from the power source

Even if the neutral is not disconnected, if you make, with your body, a
parallel conductive path from the neutral to ground, *most* of the
current in that neutral will indeed return to ground through the neutral
conductor -- but *some* of it will return through your body, as well.

Electricity follows *all possible paths*. Don't use your body as one of
them.

(either at the
service/breaker panel or in an intermediate junction box.) Any kind of a
load will make a white wire (your neutral, HOT, HOT, HOT!

And that makes your body the *only* path for the current to flow
through. Your mistake is in thinking that this is the only dangerous
condition. It's not.