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Re: comprehending electric/magnetic interactions



Thanks, I hadn't considered the importance of the non-uniformity of the
field. The standard qvxB does indeed show the ring being pushed away if
you consider the field lines diverging (assuming two like poles facing).

The energy consideration brings up another situation with which I am
struggling. A current-carrying conductor carrying a current perpendicular
to a uniform magnetic field will be pushed to the side - but why? A short
while later, the same conductor will be carrying a reduced current through
the same magnetic field, while moving to the side. The conductor now has
kinetic energy and is creating an emf opposing the original current, but
where did this energy come from?

Would it be erroneous to consider its origin as being the original emf
device? This seems to make sense numerically, but I've not seen any
experimentation of the energy flow in such a situation. Here's what I'm
thinking though -
As the velocity increases, the "back-emf" increases and consequently the
current supplied decreases; this current is the one responsible for (and
proportional to) the acceleration. The power dissipated by the back-emf
is therefore proportional to speed and acceleration, as is the rate of
change of Kinetic Energy.

The biggest problem I see with this is the convoluted energy
transformation, from the energy in the emf deveice to the kinetic energy
of the conductor, via a magnetic interaction largely independent of both.
Is there a more straightforward transfer process, maybe involving the
redistribution of field interactions with increased relative speed?

Consider a region containing a uniform magnetic
field (field lines are a constant distance apart.
. .) A small current carrying loop placed into
this region is not attracted to one pole or the
other, because at no place is its energy lower
than any other place. (This assumes the axis of
the loop is aligned with the magnetic field. )