"It has been quantitatively demonstrated that the net charge density is not everywhere zero when the current loop of Sect. 1 translates along a line in its plane. Indeed a simple proof qualitatively indicates that uncharged current loops are electrically polarized when they translate. At any given moment the translating loop has an excess of positive or negative charge on one "side," and an excess of negative or positive charge on the other. In brief, the translating loop has an electric dipole moment (as well as a magnetic moment), and consequently there is a nonzero electric field."
"This effect is only present when the loop translates. It is not present when the loop merely spins."
Frederick
More:
http://www.maxwellsociety.net/PhysicsCorner/Electrodynamics/GualaValverde%20Explanation.html
