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## Homework Statement

http://web.phys.ntnu.no/~ingves/Teaching/TFY4240/Exam/Exam_tfy4240_Dec_2013.pdf

http://web.phys.ntnu.no/~ingves/Teaching/TFY4240/Exam/Solution_tfy4240_Dec_2013.pdf

problem 2g

## Homework Equations

## The Attempt at a Solution

Hi, this is taken from problem 2g in the problem set above.

Assume you have an electric field ##\vec{E}##, and in there you have a polarized dielectric sphere. Then the sphere will have a polarization density that varies continuously in the direction of ##\vec{E}##.

Now, if you start spinning this sphere about the direction of ##\vec{E}##, will a magnetic field be induced? I.e. will the spinning surface charges induced on the sphere constitute a current that will by maxwell's laws produce a magnetic field?

It's kinda logical it should since you have moving charges, but according to my professor it won't. Reason being since the polarized surface charge distribution exhibits axial symmetry around ##\vec{E}##, apparently. But what does that have to do with anything? You still have moving charges!

Maybe he means that since these are POLARIZED charges, the netto charge is approximately zero everywhere and so the "currents" kill each other?