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Re: comprehending electric/magnetic interactions



Are you considering a uniform or non-uniform magnetic field? For a steady
current that's important.

Bob at PC


Gary Turner wrote:

Could anyone help me explain this problem that arose during a discussion
of magnetic field interactions.

Consider a simple current loop. It will produce a magnetic field and, if
brought into an opposing magnetic field (in such a way that the external
field is perpendicular to the plane of the loop), should be repelled by
it. Now, square the loop up and take three of the sides out of the region
of magnetic field. Now all that remains is a current-carrying wire in a
magnetic field, which will be pushed to the side (F=qvxB).

Indeed, a simple F=qvxB calculations shows that the loop will be
either "stretched" or "compressed" depending on the direction of the
current instead of being attracted towards, or repelled from, the source
of the external magnetic field.

It seems that the one side remaining in the field should still have a
repulsive force - if it does not apply to any one side, how can it apply
to the whole - but that would imply that there exists a force parallel to
the magnetic field in addition to the qvxB. This would have to hold
equally for a long conductor just sitting in a magnetic field.

Anyone out there considered this?