Newsgroups: sci.electronics
Path: utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: ANOTHER house wiring question (this one's basic)
Message-ID: <1991Jan12.235512.17824@zoo.toronto.edu>
Organization: U of Toronto Zoology
References: <kJhTxoE@quack.sac.ca.us>
Date: Sat, 12 Jan 1991 23:55:12 GMT

In article <kJhTxoE@quack.sac.ca.us> mrapple@quack.sac.ca.us (Nick Sayer) writes:
>What, exactly is the theory here? Ground is connected (basically)
>to a big pipe in the dirt, and hot and neutral go up to the pole,
>but some more details for a complete software weenie would be
>great.

The current flows through hot and neutral.  Ground is strictly for safety
purposes and never (deliberately) carries current.

Neutral is normally grounded at the pole.  Note, however, that with tens
or hundreds of amps of current flowing in neutral, it is *not* at ground
by the time it gets to you.  V=IR, and the wire's R is not zero.  Neutral
can be very close to ground in a house that isn't pulling much current.
(Beware, this can change unpredictably, e.g. when your housemate puts
a load of washing into the dryer.)  It can be several volts above ground
in upper floors of an apartment building; I've measured it.  Neutral is
not *as* dangerous as hot, but it should never be mistaken for ground.
This is why there is a separate ground pin, for safety.
-- 
If the Space Shuttle was the answer,   | Henry Spencer at U of Toronto Zoology
what was the question?                 |  henry@zoo.toronto.edu   utzoo!henry
