Electromagnetic induction of rotating magnets



Journal Title

Journal ISSN

Volume Title



A modified unipolar machine has been studied where the rotor conslts of two parallel magnets embedded in a superconducting lead casting. The voltage detection circuit Is well shielded with super-conducting materials and Is assured to be In zero magnetic field and insulated from the magnets. The same steady voltages as observed for the ordinary unipolar generator are measured on rotating the magnets inside a soft iron cylindrical shell at 4.2 °K. The results disagree with the conventional calculations using the polarization P = (v x M)/c[cubed], but can be explained in terms of [partial derivative]B/[partial derivative]t due to the rotation of the magnets. B of the rotating magnets at any time has been calculated by treating each magnet as if it were at rest with respect to the circuit. As time passes on, the rotating magnets undergo different orientations to give different values of B at the circuit and the resulting [partial derivative]B/[partial derivative]t induces the observed e.m.f. The analysis has been extended to show that the unipolar voltage is basically the result of an induction effect, provided the motion of the magnetic sources are followed.