ABSTRACT
The phenomenon of hysteresis was first associated with magnetic materials by Warburg. Ewing showed that the induced magnetism lagged behind the applied magnetomotive force and named this property the “hysteresis effect”. A permanent magnet will contain magnetic energy for any application, represented by the ‘size’ of hysteresis loop of the magnet material: the ‘fatter’ the loop, larger will be the energy content. The hysteresis loop is akin to the “indicator diagram” of an internal combustion engine. It often becomes necessary to obtain actual hysteresis loops, major as well as minor, of a permanent magnet material by performing suitable experiment before its in an application. Rotational hysteresis results from the rotation of a magnetic material, say a disc, through one cycle in an applied magnetising force of constant magnitude.
