On the electric effect of rotating a magnetic insulator in a magnetic field

Abstract

In a previous paper by one of us it was shown that when an insulator of specific inductive capacity K rotates in a magnetic field there is an electro­motive force induced in it equal to that in a conductor multiplied by 1 — K -1 . The object of the experiments described below was to measure the induced electromotive force in a magnetic insulator rotating in a magnetic field parallel to the axis of rotation. According to the theory based on the “principle of relativity” this induced electromotive force should be equal to that in a conductor multiplied by 1 — ( μ K) -1 , where μ is the magnetic permeability of the insulator, whereas on the theory of H. A. Lorentz and Larmor the appropriate multiplier appears to be 1 — K -1 , as for a non-magnetic insulator.