Re: simple magnets question

[Bob Sciamanda <trebor@VELOCITY.NET>]

----- Original Message -----
From: William Beaty <billb@ESKIMO.COM>
To: <PHYS-L@LISTS.NAU.EDU>
Sent: Thursday, June 24, 1999 4:22 PM
Subject: Re: simple magnets question
> . . .

> What I don't understand is, nonzero velocity relative
> to what?  Relative velocity between the electron and the field? . . .
> William J. Beaty

I'm intruding late here, but I have to interject that this question is both
historically and physically crucial to the appreciation of Maxwellian E&M as
interpreted by Einstein (and, subsequently, all of classical physics).

The discovery of the velocity dependent "Lorentz" force F = Q(VxB+E) was
hailed as a boon, since V was "obviously" the ABSOLUTE velocity of the
charge Q.  Such (absolute) velocity dependent forces would at last allow us
to measure our own absolute velocity.  Thus spake conventional wisdom:  F  =
Q(VxB+E) was only valid when all quantities were measured by the observer AT
ABSOLUTE REST.  Measurements taken by an observer in (absolute) motion were
in error, were not connected by the simple laws of physics, and needed
"correction terms" involving the observer's (absolute) velocity.

Einstein, as a menial clerk outside of the mainstream of conventional
wisdom, objected that such an observer dependent physics would be no physics
at all!  He proposed that a model be constructed in which all observers use
the same laws, and that these laws express relations among quantities as
MEASURED BY A GIVEN OBSERVER.  In F=Q(VxB+E) the quantities F,Q,V,B and E
refer to the numerical (or vector) values as measured by the human observer
who is applying this equation to HIS OBSERVATIONS.  To this end he persued
the construction of the theories of relativity.

Bottom line answer to Bill: the "nonzero velocity" is the velocity of the
electron relative to the observer (YOU).

-Bob

Bob Sciamanda
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
http://www.velocity.net/~trebor