BH M= Where x is called the susceptibility of the material(磁化率)and H is called the magnetic field intensity of the applied field..(磁场强度) B+20 Where u is called the permeability of the materialWhere  is called the susceptibility of the material （磁化率）and H is called the magnetic field intensity of the applied field.（磁场强度） Where  is called the permeability of the material