Re: simple magnets question

[John Mallinckrodt <ajmallinckro@CSUPOMONA.EDU>]

On Wed, 23 Jun 1999, William Beaty wrote:

> ... when an electron moves parallel to the face of a very large, flat
> magnet where the direction of the field is perpendicular to the face.
> The electron should "see" the relative motion of the field, and so be
> deflected perpendicular to this motion and parallel to the magnet face,
> resulting in a circular path.

All an electron ever "sees" (in the sense of reacting to by virtue of its
charge) are electric fields.  It is the observer who may see an electron
"moving through" and reacting to a magnetic field.

> ... Relative to the electron, a moving field is not the same as a
> stationary field.

But what does it mean for a field to move?  Hannes Alfven (whose namesake
magnetohydrodynamic waves have often been likened to the "plucking" of
magnetic field lines) himself, warned against the danger of imagining
fields to "move" rather than "change with time."

I think these same difficulties (which ultimately bear on issues related
to Mach's principle and the existence of absolute rotational as opposed to
translational velocity) lurk behind the fantastic claims of the late Bruce
DePalma for his "N-1 Homopolar Generator."

John
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