Re: Power Lines

[John Clement <clement@HAL-PC.ORG>]

> I was like what kind of an idiot would want to stand on a high
> pwer line....(okay maybe not so tactful)
> But would you get electricuted?
> I would think that if the current went foot-to-foot you would be
> okay, but who really wants to take that chance?

Some students have seen too many cartoons.  Did you ever see Dumbo?  Dumbo
lands on some powerlines!

In reality most students don't really have a clue to reality, but the
question is actually a good one.  The student asked a what if question,
which is an extremely important aspect of thinking logically.  In other
words he was using hypothetico-deductive reasoning.  He was making an
excellent logical jump, even if the image was a bit bizarre.

Incidentally, the usual problem is that when you are grounded the current
can flow through you to the earth if you touch only 1 wire.  This situation
is not quite the same in other countries.  When I was in Mexico I got shocks
from a water fixture in my room.  They called out an electrician who fixed
it by switching the wires coming into the house.  It seems they don't use
grounded circuits, or they use them only sometimes in Mexico.  This means
that it may be possible to electrocute yourself by touching any wire.  In a
US grounded circuit the white wire is safe or neutral, and can be touched
safely.

I suspect there are other advantages to proper grounding besides safety.
For example it may reduce electrical static.  However it also can result in
some funny effects.  If you have metal waterpipes it is possible to have
current flowing through them, and the EM field can be detected.  This can
cause low frequency radiation in your home, which some people have claimed
is harmful.  The evidence is controversial, very scant, and statistically
insignificant!  I had the experience that some very low loss shielded signal
cables had a low enough resistance over 250 m that the signal had a huge
several volt AC hum on it.  We broke the loop by inserting a length of
shielded cable which was wound on a toroidal choke.

John M. Clement
Houston, TX