Re: Potentially stupid question about AC

["Dave" <dave-ster<nospam>@usa.net>]

> So both hot and neutral wires carry current, correct?  The
> difference is that the neutral wire is also grounded (at the
> unity pole where the transformer is)?  So how does the
> polarized plugs work (is the something in the appliance
> connected preferentially to one lead rather than the other)?
>
> I'm asking because I used to be called to install household
> fixtures for relatives and I used to always connect the wires
> any which way.  I mean, polarity did not seem to matter
> since the appliances always worked either way.  Now it
> turns out there is a safety concern.  Why?

Hot wires are the source of electrons, and the neutral wire carries them
back to the power plant.  So, while both carry electrons, only the hot is a
source of electrons.  Electrons are lazy little dudes and take the easiest
path home (the power plant or ground), and after they get into the neutral
line have a pretty easy trip through it.  That's why you won't really get a
shock if you touch the neutral line.  Traveling through you isn't bound to
be as easy as traveling through a wire.

Polarized plugs came into existence before the modern 3 prong sockets we
have today.  So, back when there were only 2 prongs, they did a form of
grounding were they tied the neutral line to the metal frame of the
appliance (at least this was the theory).  That way if the live wire somehow
touched any metal part, you wouldn't get a shock, because the current would
be diverted.  However, if you were replacing the plug on an appliance and
didn't connect the wires correctly, you would "electrify" the metal casing.
I think this is were some of the home-handyman comedy routines from the past
came from.  The helpful husband would fix the plug on the lamp, but when he
tried to turn it on, he would get shocked.  This form of grounding is no
longer used, because the modern method is much safer.  The polarized plug
does have other uses, though.  Let's go back to the lamp.  If you've ever
looked at a lamp socket, you'll notice two metal parts: the metal threads
and the metal "button" at the bottom.  Which might you be more likely to
accidentally touch?  Yeah, the metal threads.  So, you wouldn't really want
to hook the hot wire up to that part.  If you instead hooked the neutral up
to it, then an accidental touch wouldn't have the same repercussions.  A
polarized plug makes sure you plug the hot wire to the "button" each time
you plug it in, instead of a 50-50 chance if it wasn't polarized.

Hope this helps.

-David