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Re: mag field of infinite wire



1. Reverse the direction of the current. According to Ampere's law,
we require B to consequently change sign. But reversing the current
is equivalent to rotating space by 180 degrees so that the wire flips
end-to-end. This properly reverses the sign of the azimuthal and
longitudinal components of B, but not of the radial component. Hence
there can't be a radial component.

With the assumption that we have an infinite wire, can we not easily state
that we are at the center of the length of wire? Once that's made, we also
lose the longitudinal dependence due to symmetry. That would leave us with
the azimuthal dependence we want...

-G-

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Dr. Gordon P. Smith
Visiting Professor of Physics and Astronomy
Appalachian State University
Boone, NC 28608