The Change in Thermal Energy Which Accompanies a Change in Magnetization of Nickel

Abstract

A new method is described for measuring the very small changes in thermal energy which occur when the magnetization of a ferromagnetic substance is altered. The method is applied to an investigation of the phenomenon as it appears in a specimen of hard drawn nickel rod. As the nickel is carried through a half cycle of magnetization, commencing with maximum magnetization, the thermal energy decreases until (approximately) the knee of the hysteresis curve is reached. This is followed by a large increase as the steep part of the curve is traversed, and then by a much smaller increase as the half cycle is completed. The behavior of nickel is in contrast with that of carbon steel, for which Ellwood found an increase in thermal energy over the initial stage and a decrease over the final stage of this process.