I'll elaborate a bit on John D's last remarks, I think we are more or
less on the same page now, but . . . (just to make sure)
|
| The question makes sense only in a particular frame, because
| the decomposition of F into a spacelike part (B) and a
| timelike part (E) only makes sense w.r.t a particular frame.
|
Of course, since the question does the magnetic force do work only makes
sense in a specific frame where we can decompose F into E and B pieces.
|
| Of course the question "did work get done" is frame-dependent in
| a big way.
Agreed, which is why if magnetic forces do no work, its important that,
what is B?, be frame dependent as well.
| This is neither completely the same nor completely different
| from my earlier point that you can do magnetic work on the
| permanent dipole moment of elementary particles. An electron
| is *not* just a test charge; it has a magnetic moment, too.
|
This is a different question; though certainly very germane to my
students original question, and hence my original post.
Spin is a Quantum Mechanical effect as I understand it. So it seems
very interesting to me that in the classical world we have that magnetic
forces do no work (non-existence of magnetic monopoles being understood
in the statement); but the quantum world obviates that admonition.
I'm guessing there may be something deep in that; but I'm too dense
(don't understand QED enough) to say much more.