Magnetism Summary

MAGNETISM Basic Electrical Theory Generally, different types of materials have different values of reluctance (Figure 25). Air gap is the air space between two poles of a magnet. Since air has a very high reluctance, the size of the air gap affects the value of reluctance: the shorter the air gap, the stronger the field in the gap. Air is nonmagnetic and will not concentrate magnetic lines. The larger air gap only provides space for the magnetic lines to spread out. Summary The important information contained in this chapter is summarized below. Magnetism Summary Magnetic flux - group of magnetic field lines that are emitted outward from the north pole of a magnet Magnetic flux density - amount of magnetic flux per unit area of a section, perpendicular to the direction of the flux Weber - measure of magnetic flux Permeability - ability of a material to concentrate magnetic lines of flux Ferromagnetic materials - iron, steel, nickel, cobalt, and commercial alloys with relative permeability ranging from 50-200 Paramagnetic materials - aluminum, platinum, manganese, and chromium with relative permeability of slightly more than one Diamagnetic materials - bismuth, antimony, copper, zinc, mercury, gold, and silver with relative permeability of less than one Magnetomotive force (mmf) - strength of a magnetic field in a coil of wire dependent on current flowing through coil Ampere turns - current flowing through a coil times the number of turns in the coil Field intensity - identifies the magnetic flux density per unit length of a coil Reluctance - opposition to the production of flux in a material ES-01 Page 36 Rev. 0