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

["Bob Sciamanda" <trebor@winbeam.com>]

Bob LaMontagne asked:
> But my question is how we justify the answer to this narrowly posed 
> question
> in terms of the E&M available in an introductory physics course. Where 
> does
> the electric field that the (assumed stationary) proton experiences come
> from since there is no time varying magnetic flux from a uniform field?
Maxwell's equations connecting fields and sources apply in each inertial 
frame.  When you transform to the proton's rest frame, you also see 
transformed sources (Helmholtz coils, etc).
These transformed sources will account for the transformed fields by means 
of Maxwell's equations.

These transformations involve more than the bare Maxwell equations - they 
require the relativistic implications/consequences of those equations.  For 
an inquisitive introductory class, you might want to appeal to time dilation 
and length contraction to illustrate these transformations in a few very 
simple cases.

Bob Sciamanda
Physics, Edinboro Univ of PA (Em)
http://www.winbeam.com/~trebor/
trebor@winbeam.com