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From: cmcmanis%pepper@Sun.COM (Chuck McManis)
Newsgroups: sci.electronics
Subject: Re: resistance of earth ground
Message-ID: <22416@sun.uucp>
Date: Tue, 30-Jun-87 14:38:19 EDT
Article-I.D.: sun.22416
Posted: Tue Jun 30 14:38:19 1987
Date-Received: Wed, 1-Jul-87 06:32:06 EDT
References: <1315@cullvax.UUCP> <327@fornax.uucp> <1569@midas.TEK.COM>
Sender: news@sun.uucp
Reply-To: cmcmanis@sun.UUCP (Chuck McManis)
Organization: Sun Microsystems, Mountain View
Lines: 50

Well to put in my two cents worth, lets look at the problem again..

First, the original poster stipulated electrodes that consisted of
two chevettes, one dropped into the Pacific ocean and one dropped
into the Atlantic ocean. 

Right off the bat we can determine that little or no current will
flow through the continental United states because the oceans 
are a pretty decent electrolyte and connected at both the arctic
ocean and the Cape of Good Hope. This circuit can be modelled as :

                     __________________________
                    /        U.S.of A.         \
Chevette 'A' o-----+----------/\/\/\------------+----o Chevette 'B'
                    \__________________________/

As you can see, no current flows in the US because it is 'shorted' by
the oceans.

Secondly assuming you dropped the chevettes into the dirt somewhere
and they did manage to set up a current flow, someone else claimed
'if the resistance were zero every time a powerline fell down it 
would electrocute everybody.' or something to that effect. Which
I don't believe primarily because I have been within 100 yds of a
downed high voltage wire and not suffered any ill effects. However
in the interest of science I offer the following model :

             |                                    /
             \ <---- You, and open               /
             /       circuit resistor.          / <--The power line
             \                                 /
             /                                /
_____________|_______________________________/______
      __|__             __|__     ^              __|__
     / / /             / / /      |             / / /
                                  |
                              The Ground

As you can see, no current flows in you because you develop no potential.
(no this isn't a slur on ones abilities!)

These are of course the simplest cases and there are lots of other things
that one should consider, such as 'is the voltage varying with time, and
if so why didn't you use an impedence model?' or 'What about the skin
effect of charged bodies, and the potential for coronal discharge?'
These we leave as an exercise for the reader.

--Chuck McManis
uucp: {anywhere}!sun!cmcmanis   BIX: cmcmanis  ARPAnet: cmcmanis@sun.com
These opinions are my own and no one elses, but you knew that didn't you.