Internal Friction in Solids V. General Theory of Macroscopic Eddy Currents

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Abstract
In vibrating ferromagnetic metals macroscopic eddy currents tend to shield the interior of the metal from changes in magnetic induction. The dissipation of energy by these eddy currents contributes to the internal friction of the metal. This internal friction has previously been investigated theoretically only for longitudinal vibrations, and only the asymptotic formulae for high and low frequencies have been found. In this paper this internal friction is calculated for all frequencies for both longitudinal and transverse vibrations. The theory of internal friction due to macroscopic eddy currents is shown to be formally identical with the theory of internal friction due to macroscopic thermal currents. The methods developed by the author for the study of thermoelastic internal friction are thus directly applicable to the study of the macroscopic electric eddy currents.