Demagnetizing Factors of Rods

A chart is constructed for converting the apparent magnetic permeability to the true permeability of cylinders of any given ratio of length to diameter. The curves are based on previous calculations in which account was taken of the variation of the demagnetizing factor N with permeability, but in which the permeability was assumed constant over any one cylinder. The flux distribution has been determined experimentally in several cylinders, and as the field acting on the specimen is increased from zero, the positions of the effective poles have been found to move toward the middle of the rod until (if the permeability is sufficiently high) they are located about 0.7 of the distance from the middle to the ends, and then to move toward and approach the ends as limits as the permeability declines in high fields.