A phenomenon of magnetization of iron. It may be attributed to a sort of
internal or molecular friction, causing energy to be absorbed when iron
is magnetized. Whenever therefore the polarity or direction of
magnetization of a mass of iron is rapidly changed a considerable
expenditure of energy is required. It is attributed to the work done in
bringing the molecules into the position of polarity.

The electric energy lost by hysteresis may be reduced by vibrations or
jarring imparted to the iron, thus virtually substituting mechanical for
electrical work.

On account of hysteresis the induced magnetization of a piece of iron or
steel for fields of low intensity will depend on the manner in which the
material has been already magnetized. Let the intensity of field
increase, the magnetization increasing also; then lower the intensity;
the substance tends to and does retain some of its magnetism. Then on
again strengthening the field it will have something to build on, so
that when it attains its former intensity the magnetization will exceed
its former value. For a moderate value of intensity of field the
magnetization can have many values within certain limits.

Synonym–Hysteresis–Hysteresis, Static–Magnetic Friction.