Re: induced emf and eddy currents

[Nick Steph <stephn@franklincoll.edu>]

Others have written, in part:

> least partially dispose of "motional emf" by noting that we are trying to
> do the standard path integral of E in a frame in which the path itself is
> moving.  If we do that integral in the proper frame we will find a
> background electric field (v x B) which precisely accounts for the
> observed emf.

Since I have been following this most interesting thread for a few days, I 
have been waiting for the "frame of reference" consideration to come up.  I
believe that Einstein's special relativity comes up here as some people 
think the F = qvxB moves the charges; while others think it is due to a 
change in magnetic flux.  Depending, of course, on their frame of reference.

Here is where I get confused:  Consider a conducting rod of length L, moving
perpendicularly through a UNIFORM magnetic field, B, at a constant velocity,
v.  An observer in the lab will detect a potential difference across the rod, 
PD = BLv.  What about an observer on the rod?  According to special relativity,
she must detect it also; but what does she consider to be the cause?

In passing, I must say that I enjoy this 'service' and give thanks to those
who boldly post; even when I disagree with them.  It is not without some
trepidation that I make my first post after two months of lurking.
Thanks,
Nick
**********************
* Nick C. Steph       *
* Franklin College     *
* Department of Physics *
* Franklin, IN   46131 *
* Phone: 317-738-8308 *
* Fax:	317-738-8310 *
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