Re: [Phys-l] Force on a charged particle from a magnetic field

["Bob LaMontagne" <rlamont@postoffice.providence.edu>]

> -----Original Message-----
> From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
> bounces@carnot.physics.buffalo.edu] On Behalf Of John Mallinckrodt
> Sent: Tuesday, November 28, 2006 2:01 PM
> To: Forum for Physics Educators
> Subject: Re: [Phys-l] Force on a charged particle from a magnetic field
>
>
> But there is time varying flux in the frame of the proton.  The only
> way to avoid that involves using an infinitely large magnet.

That's why I carefully defined the magnetic field to be uniform, so there is
no change in flux with time (classically). Specifically, how do you get the
time varying flux that ultimately produces an electric field to move the
proton? (Again, without an appeal to relativity.)

> Maxwell's equations have relativity built into them so they are, in
> principle, fully capable of answering the question.

I thought that the Lorentz transformations came about through Einstein's
attempt to make Maxwell's equations apply to any inertial frame of
reference.

Anyway, I agree with most of the responder's claims that relativity is
required - and, as Skip said, that was what Einstein was trying to do a
hundred years ago. I am just uneasy with the way various textbook author's
present this example (or a variation of it) before relativity is introduced,
and then expect students to be comfortable with the answer. And yes, it does
seem to provide a great segway into relativity.

Thanks to all who took the time to respond.

Bob at PC