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Re: magnetic lines like these?



But wires carrying current are also electrically neutral, and yet can
produce a magnetic field. See the explanation in Purcell's Berkeley book.
Since magnetism is a relativistic effect the velocity is critical.

On Tue, 12 May 1998, Tim Folkerts wrote:


Oh yes, this is important, I think. If protons and electrons have the
same KE (meaning very different v) then traveling in the same direction
does not mean that the net B is zero. In a neutral plasma electrons
will contribute much more to B than protons.

Really?

The CURRENT from the positive and negative charges must be the same (or
the sun would be acquiring a net charge). The electrons are moving
faster, but are farther apart. Biot-Savart says that B is proportional
to I. Thus it seems that the two contributions must be equal (in
magnitude anyway), producing a net B = 0.

Or am I missing something?



--- Tim Folkerts


********************************************************
Timothy J. Folkerts Tim.Folkerts@valpo.edu
Dept. of Physics & Astronomy 219-464-6634
Valparaiso University
Valparaiso, IN 46383