Coercive or Coercitive Force

The property of steel or hard iron, in virtue of which it slowly takes up or parts with magnetic force, is thus termed ("traditionally"; Daniell). It seems to have to do with the positions of the molecules, as jarring a bar of steel facilitates its magnetization or accelerates its parting, when not in a magnetic field, with its permanent or residual magnetism. For this reason a permanent magnet should never be jarred, and permitting the armature to be suddenly attracted and to strike against it with a jar injures its attracting power. Coercive force is defined also as the amount of negative magnetizing force required to reduce remnant magnetism to zero. By some authorities the term is entirely rejected, as the phenomenon does not seem directly a manifestation of force.