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Home Electromagnets Permeability and Saturation of Iron  
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Permeability and Saturation of IronAuthor: E.E. Kimberly
The permeability of a vacuum, air, or any one of many other media is a constant, regardless of the flux density in it. The permeability of iron, nickel, cobalt, or any one of several of their alloys is a variable function of the flux density in it. Fig. 73 is a typical magnetization curve of flux density B in iron plotted against H Which, from equation (71), is times the ampereturns (NI) used foreach centimeter of length. For convenience, the magnetization curves for commercial iron are usually given as gausses plotted against ampereturns per centimeter of length of path. Beyond the point a, Fig. 73, called the knee of the curve, the increase in B for a given increase in H becomes very small. It is quite possible, but seldom practicable, to carry the magnetization beyond the point b. In calculating the number of ampereturns required to magnetize a piece of iron to a certain flux density, the permeability of the iron at that flux density must be known, or a curve of NI per unit length of path plotted against flux density must be available for the specific magnetic material being used.


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