CHAPTER 10 - MAGNETIC FIELDS AND CIRCUITS

Abstract

This chapter discusses the magnetic fields and circuits. In many magnetic circuits, having two or more parts in series, with different cross sections, and/or different materials, approximately the same flux passes through each section. Some leakage flux may bypass a section by a parallel path in air, just as electric current may leak through an insulator in parallel with the main circuit of conductors in series. The reluctance of each part of a series magnetic circuit can cause a magnetic potential drop (m.p.d.) along its length and require a part of the magnetomotive force (m.m.f.) to maintain the flux. For each part, the m.p.d. = flux × reluctance, just as electrical p.d. = current × resistance. The chapter also discusses numerical problems on suspended magnets. A suspended magnet behaves very much like a pivoted coil carrying current in a magnetic field. The continual spin of electrons in the atoms of the magnet provides the magnet with the equivalent of a current in a coil around it. Thus, the long, straight arrow may represent either a pointer along the axis of a coil, or a suspended bar magnet, turning into line with the flux.