Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: electron magnetic moment



Justin Parke wrote:

My question had more to do with the potential energy
associated with the electron's magnetic moment.

OK.

In the example of an electron orbiting another object
via a hinged force of constraint, it was this force of
constraint that did work

Some of the work.

and was responsible for the potential energy.

Some of the potential energy.

In the case of a spinning, rather than an orbiting, electron,
what is the force of contraint that does work?

It depends on what work you are talking about.

In the case of the macroscopic hinged system, you can hook
a crank to the hinge (crank axis perpendicular to hinge axis)
and turn the crank to flip the dipole moment. Cranking is
easy in this case, but maintaining constant current of the
orbiting charge requires a bit of mechanism.

In the case of an elementary particle, maintaining constant
current (constant dipole moment) is easy, but cranking is
hard. You have to use magnetic resonance techniques or
some such -- time dependent perturbations and all that.
There's no crank and no hinge, so it's hard to answer the
question as stated.

But the question remains a good one; let me attempt to capture
the spirit of the question by restating it: Consider flipping a
superconducting ring containing a nonzero amount of trapped flux.
This has a built-in constant dipole moment, rather analogous to
an elementary particle. The laws of quantum mechanics maintain
the constant flux for us. And we can attach a crank to it.

Constant flux in the loop corresponds to a !!non-constant!! energy of
the current-carrying electrons. Typically very little of the change
in energy is in the kinetic energy of the electrons per se; most
of it is in the magnetic field induced by the electrons ... but
it is conventional (and harmless) to be somewhat sloppy and attribute
the energy to the electrons.