The relation between the Wiedemann effect and the Joule magnetostriction effect

NASA Technical Translation, 1968. 17 p. Translation of "Relation Entre L'Effet Wiedemann et L'Effet Joule de Magnetostriction". In: Journal de Physique, Vol. 14, No. 1, pp. 13-24, 1926.Wiedemann's magnetic torsion is a special case of Joule's magnetostriction. A cause and effect relation can be established between these two phenomena, provided all the deformations produced in the Joule effect by the inductor field are taken into account.In Wiedemann's experiments a tube is inserted into a helicoidal field which causes dimensional variations in all directions parallel to the field (the longitudinal Joule Effect) and perpendicular to it (the transverse Joule effect). The study of these two effects shows an asymmetry which results in a twisting of the tube, and leads to an equation which accounts for all the peculiarities of the Wiedemann effect; in particular, it construes the existence of a maximum torsion and an inversion point for some fields different from those which produce some analogous effects in the Joule phenomenon.The torsion inversion is produced when the coefficients of the transverse and longitudinal Joule effects are equal and of the same sign.The composite curve of the Wiedemann effect, obtained from those of the two individual Joule effects, is in good accord with the experiment.