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Re: [Phys-l] induced electric field



Disclaimer: This is a nibble at the very edge of this problem...

I immediately associate a uniform magnetic field into the page,
as associated with a circular electric field in the plane of the paper...
This is not what you would call azimuthal, I don't think.

If I take a cross section of a toroidal transformer,
i expect the electric field to look much the same if the
cross section is square or round.

Brian W

Carl Mungan wrote:
A standard textbook problem says: Assume a uniform magnetic field (B) pointing into the page inside a circular region of radius R (and zero outside of it) and increasing in magnitude at a constant rate (dB/dt). Find the induced electric field (E) everywhere in space.

For specificity, assume the B field is produced by an ideal solenoid. One finds by symmetry that E is azimuthal in direction, increasing linearly from zero for r<R up to (R/2)(dB/dt) in value, and then dropping off as the inverse square outside the solenoid.

Fine, now what happens if the solenoid is square in cross-section? (This question was asked by a student.) Say length L on a side, and still ideal so B uniform inside and zero outside with constant rate of increase of strength.

Regardless of whether I try the differential or the integral form of Faraday's law, I don't seem to make much progress. Who can help me out? If this variation is done in some reference, that would be helpful too. -Carl