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Ripperbat
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Homework Statement
A rod of dielectric material is spun about it's axis with angular velocity [tex]\omega[/tex]. A uniform magnetic field B exists in a direction along the axis of the bar. Determine a charge distribution which produces the same electric field as does the rotating rod. The electric susceptibility of the material is xE
Homework Equations
The Attempt at a Solution
The force on a charge q at a distance r is F=q*[tex]\omega[/tex]*r*B and the electric field is E=r*B*[tex]\omega[/tex].
The polarization of the rod at distance r is P=xE*[tex]\epsilon[/tex]0*[tex]\omega[/tex]*B*r.
So the volume distribution of charge should be -div P = -([tex]\partial[/tex]Pr) / ([tex]\partial[/tex]*r). But according to the book it should be
-div P = -([tex]\partial[/tex]Pr) / ([tex]\partial[/tex]*r) - (Pr) / r .
Could somebody please explain why it should be that way?? thx