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Re: Park City Paradox ?



Could you view the situation in the following way?

Consider two electrons moving side by side at the speed of light. At that
speed, each electron has an electric field but the "information" about the
changing field of one electron (due to its movement) cannot "keep up" with
the other electron. Consequently, the two electrons do not "see" each
other, even though they are (from our perspective) side-by-side. From our
reference frame, we see no force between the two electrons. We "explain"
the lack of a force by saying that a magnetic attraction exists that exactly
balances the electric repulsion. At lower speeds, the magnetic attraction
is less and the electrons do repel but less than what would be predicted by
the electric force alone.

A lot of hand-waving, I admit, but is it sound?

P.S. I apologize if you receive this message twice - apparently my first
post didn't make it.

--------------------------------------------
Robert Cohen rcohen@po-box.esu.edu
570-422-3428 http://www.esu.edu/~bbq
Department of Physics
East Stroudsburg University
East Stroudsburg, PA 18301
--------------------------------------------

-----Original Message-----
From: Hugh Haskell [mailto:hhaskell@MINDSPRING.COM]
Sent: Sunday, January 06, 2002 10:29 PM
To: PHYS-L@lists.nau.edu
Subject: Re: Park City Paradox ?


At 15:36 -0700 1/5/02, Ludwik Kowalski wrote:

Is this a paradox or not? I was skiing down
on the left side of another skier this morning.
We were moving in the same direction with the
same speed. And I was speculating:

1) Suppose each of us was charged negatively.
Being at rest with respect to each other we
would repel each other by Coulomb's law.

2) But electrons drifting along two parallel
wires in the same direction produce an
attractive force between the wires.

This is true, but it is relatively easily shown that this is a
relativistic effect (even at the very low drift velocities of the
electrons). The key of the analysis is that, although the net charge
on a wire carrying a steady state current is zero, the wire (less the
negative charge of the electrons that comprise the current) is
positively charged. The net attractive force between the wires is due
to the apparent increased charge density of the oppositely charged
objects in the other wire (this is the relativistic effect).
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