Teaching the magnetostatic field: Problems to avoid

A widely recognized problem that physics teachers encounter is the difficulty that most students have when solving problems related to magnetic field line distributions in the presence of hard- and softmagnetic materials. Two causes of these difficulties are identified: (1) The fact that the hysteresis is introduced as the typical behavior of ferromagnetic materials; (2) the fact that the magnetic field strength H is almost absent in the electromagnetism course. Proposals to remedy the student’s problems are (a) to introduce four idealized magnetic materials, i.e., unmagnetic, hardmagnetic, softmagnetic, and superconducting materials; and (b) to use the magnetic field strength H, and not the magnetic induction B, when discussing problems of magnetostatics.