Magnetic hysteresis can be characterized in various ways. In general, the magnetic material is placed in a varying applied H field, as induced by an electromagnet, and the resulting magnetic flux density (B field) is measured, generally by the inductive electromotive force introduced on a pickup coil nearby the sample. This produces the characteristic B - H curve; because the hysteresis indicates a memory effect of the magnetic material, the shape of the B - H curve depends on the history of changes in H.