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Re: Electrical Wire Safety




I see it it clearly: John is winding a Wimshurst machine
to a hand-holding ring of students:
"This is you making contact with a live wire"....
[winding furiously],
"And this is you making contact with a live wire wearing
rubber gloves and boots..."

And leering evilly .... Not a bad analogy, but a bit stretched. One can
easily teach a young child the meaning of hot by letting them touch
something hot such as the outside of a hot coffee cup and saying hot. The
sensation is unpleasant to the child, but not dangerous. Beyond that there
are too many situations which can be dangerous where individuals can get
into trouble, and there are many situations which are safe, which people
think are dangerous.

It is surprising how many students express apprehension when working with
ordinary batteries. Then there was the group in my class who inserted a
clip lead into the two slots of a switchable outlet, and then switched it
on. I also picked up a paper clip which had obviously been fashioned for
insertion into an outlet in the middle of my floor. Students have certainly
been told about the dangers of electricity and are aware that doing things
like putting paper clips into outlets can be dangerous, yet the message does
not get through.

So the 5 minute warning about not touching wires, or using metal objects
around wires is certainly a reasonable thing, but it is not that effective.
Consider how many people have persisted in using electrical appliances in
the bathroom around the bathtub and then electrocuted themselves. The
warnings are legion against this, yet it continues to happen. Putting
pennies into fuse boxes used to be popular, but now with breakers this is
impossible. Instead they just pull the low rated breaker and install one
with a higher current rating.

Again, the problem is that just telling them it is dangerous does not give
the message across very well. One can not see the deterioration of the
insulation on the wires in the wall from overheating, so it appears to be
safe until the house burns down.

This is a very similar problem to the one of getting students to understand
Newton's third law. The students have a paradigm which is at odds with the
standard scientific one, and it requires a lot of work to convince them to
change the way they think. Lectures do not work very well at changing
paradigms.

Incidentally the discussion of the electrical wiring in the US could have
been brought into better focus if it had been contrasted with countries
which do not follow the standard codes of safety. The grounded system that
we have in the US actually promotes better safety. Apparently in Mexico
they do not follow the same code. It is possible that they theoretically
follow the same code, but in practice they don't. The house that I was
staying in was "modern" construction, but had a wiring problem. I was
getting shocks from the handles of the shower in my room. The owners called
in an electrician. He fixed it by just reversing the two wires coming into
the house. Apparently there was no fixed neutral/hot designation. I was
told at that time that the practice of having one side of the wiring
attached to ground was not common in Mexico. This was over 40 years ago,
but I doubt things have changed much since then.

Then of course there are the workers who cut underground wires and attempt
to fix them themselves ...

John M. Clement
Houston, TX