Poynting’s theorem deals with the conservation of energy in a electromagnetic field, and is typically applied to stationary circuits or circuit elements. A team of researchers has now applied the theorem to the homopolar generator. Instead of being stationary, the homopolar generator is a conductor moving in a background magnetic field. Their results reveal new information about how magnetic braking arises within Poynting’s theorem.

The study was supported in part by the Exobiology & Evolutionary Biology element of the NASA Astrobiology Program.

The paper, “Energy conservation and Poynting’s theorem in the homopolar generator,” was published in the American Journal of Physics