Energy conservation and Poynting's theorem in the homopolar generator

Abstract

Most familiar applications of Poynting's theorem concern stationary circuits or circuit elements. Here, we apply Poynting's theorem to the homopolar generator, a conductor moving in a background magnetic field. We show that the electrical power produced by the homopolar generator equals the power lost from the deceleration of the rotating Faraday disk due to magnetic braking and review the way that magnetic braking arises within Poynting's theorem.