Increase of Residual Magnetism Caused by a Current Flowing Through an Iron Bar

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Abstract
If a bar of high grade wrought iron or of permalloy is placed in a sufficiently strong magnetic field, and if this field is abruptly reduced to zero, a current set up in the iron causes an increase of the residual magnetism. This effect is not obtained when the field is gradually eliminated, nor is it obtained when the current flows in a wire along the axis of a bored out iron cylinder unless the cylinder is slotted longitudinally. Then the increase of magnetism is again observed. There seem to be two effects involved in this phenomenon. One of these results in decreasing the residual magnetism in accordance with Wiedeman's and Villari's observations, and is apparently associated with the circular flux set up in the bar by a current sent directly through it or in a separate wire along its axis. The other effect, if it could be completely isolated, would probably produce only increases in residual magnetism, and seems to depend on an unstable condition of the magnet.

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