Re: voltage question.....

Mark wrote:
On Nov 6, 8:29 pm, Muzaffer Kal <k...@xxxxxxxxx> wrote:
On Fri, 06 Nov 2009 14:33:26 -0600, "fisico32"

<marcoscipio...@xxxxxxxxx> wrote:
hello Forum,
a question regarding the way voltage "works" in a particular transmission
application.
In the mountains, I have seen power transmission power lines that use only
one metal wire. The second wire (return wire) is represented by earth,
i.e., the first wire is stuck straight into the ground.
Isn't that equivalent to complete the circuit with a incredibly large
resistance that dissipates a lot of power?
Imagine earth as if it's an arbitrarily large reservoir of electrons.
You can take or give as many as you want on each end; actual electrons
need not move (much). So that's not an incredibly large resistance, in
fact can be made as small as a couple of hundreds of milli-ohms.
--
Muzaffer Kal

DSPIA INC.
ASIC/FPGA Design Services

http://www.dspia.com

I think you will find that there is not just a wire "stuck into the
ground" but that the wire leads to a buried ground wire, that actually
connects the poles with a metallic connection. You are correct,
relying on the "earth" to complete the ground connection would create
a large lossas well as a hazard. I remember playing under
transmissions line one time as a kid and there was a small creek and
there was a large uninsulated grounding cable that ran across the
stream apparently interconnecting the towers.

field telephones used in WWI relied on a ground (earth, for Brits) return. It was possible to listen in by driving two stakes into the ground a few hundred yards apart with the help of a vacuum tube amplifier. Nowadays, mains hum would overwhelm the signal and make single-wire telephony too noisy to be practical.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
.

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