----- Original Message -----
From: "Ian White, G3SEK" <G3SEK@ifwtech.co.uk>
To: <amps@contesting.com>
Sent: Saturday, February 08, 2003 2:31 AM
Subject: Re: [Amps] Voodoo Magnetic Fields
> Jeffrey Madore wrote:
> >As I alluded to, I think we can leave the terrestrial magnetic field
> >out of the equation.
>
> That is clear from Eric's calculation.
It is?..."geomagnetic" ?
----- Original Message -----
From: <MorgusMagnificen@aol.com>
To: <amps@contesting.com>
Sent: Friday, February 07, 2003 7:19 PM
Subject: [Amps] Voodoo Magnetic Fields
> Let's calculate (not speculate) on the (Lorenz)force acting on a welding
> cable laying at ground 0, and one-meter long, carrying a current of
1000A.,
> due to its interaction with the geomagnetic field, which we will assume to
be
> vertical and of magnitude B=1Gauss (good estimates - just ask your
friendly
> geophysicist). Of course, we all recall that the formula for the force on
a
> straight conductor in a B-field is:
>
> F=BxLxI (MKS units)
>
> Using MKS units: F=.00001 x 1 x 1000=.01N.=.0022Lbs=.032Oz.
> Should really shake up that 4/0! Remember - this is the total force on
> 1METER of cable, with 1000AMPS flowing.
>
> Eric von Valtier K8LV
> >A length of power cable in free air exhibits the property of inductive
> >reactance when there is AC current flow. This XL results when the
> >cables own magnetic field expands and collapses about the conductor
> >itself. The result is a CEMF which produces current that is out of
> >phase with the source current and thus bucks or impedes the flow of
> >current from the source. Hence, we have these two current components
> >which are out of phase, producing magnetic reaction and mechanical force.
> >
> If you can describe the scenario, you can predict the force. Please may
> we see a calculation?
No, Ian, I can't fully describe the scenario nor will I claim to completely
understand it. All I have stated is an explanation of my experience, using
*basic* electromagnetic theory as it relates to conductors. When it comes to
rapidly changing current conditions and associated magnetic forces, there
are often many variables to be examined; some of which are not readily
apparent.
I've always found it important to have a thorough understanding of what I
can see, before I attempt to explain what I can't see, with textbook
formulas. I've often seen calculations used to overly simplify a very
complex situation, resulting in erroneous conclusions and theories. These
then get written as facts, which only lead to further misunderstanding and
it's consequences. So no, I do not feel qualified to provide a calculation.
There once was a time when I thought I knew so much...when I thought I could
do anything. The years have brought me to a place where I realize how little
I do know and how impotent I am. That is precisely why I'm here and why I
listen far more than I try to contribute. I have great respect for, and have
gained considerably from many of the knowledgeable people on AMPS, yourself
included.
Jeff - K1LE - CT ><>
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