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BELL SYSTEM TECHNICAL JOURNAL 



measurements the rings were wound with insulated copper wire after 

 being placed in thin annular wooden boxes to protect them from strain. 

 Hysteresis losses were computed for a few alloys from effective re- 

 sistance measurements at low flux densities, made on wound rings. 



Magnetization and permeability curves and hysteresis loops were 

 plotted from ballistic galvanometer measurements. Galvanometer 

 measurements also were made on a few alloy rods 11 in. long and 

 1/8 in. diameter, at a magnetizing force of 1500 gauss. For these 

 measurements the rods were placed in a long solenoid and the induction 

 measured by means of an exploring coil at the center of the rod. 



Properties of the 45 Per Cent Ni, 25 Per Cent Co, 

 30 Per Cent Fe, Composition 

 Measurements for the composition 45 per cent nickel, 25 per cent 

 cobalt and 30 per cent iron in the annealed condition are plotted in 

 Figs. 1-7 and tabulated in Table I. The curves in Fig. 1 illustrate 

 the permeability characteristics for this composition (No. 858-1) and 

 for a sample of annealed Armco iron. For magnetizing forces below 

 1.7 gauss, the permeability is substantially constant, the variation 

 being less than 1 per cent. This constancy is remarkable for a 

 magnetic material having an initial permeability nearly double that 

 of iron. Within the same range of field strengths the permeability 

 of the iron sample rises from an initial value of 250 through a maximum 

 of 7,000 at a magnetizing force of 1.3 gauss and decreases to 6,300. 



TABLE I. 



Hysteresis Loss with Different Heat Treatments for [45% Ni — 25% Co — 

 30% FeJ Composition Perminvar 



