Temperature Coefficient of Magnetic Permea - Bility within the Working Range

The development of methods and apparatus for magnetic measurements capable of an accuracy of i per cent makes it necessary to consider factors which have heretofore been considered negligible. One of these factors, the temperature coefficient of magnetic permeability, is the subject of the present paper. Many workers have studied the effects of temperature on the magnetic permeability of iron and steel. All of the investigations, however, have been carried on with special reference to temperatures far removed from the atmospheric range. However, Bauer, 1 Hopkinson, 2 Terry, Burrows, and a few others have made some observations at temperatures between o and ioo° C. which show that induction curves at two different temperatures in this region cross each other. For low inductions the magnetizing force necessary to produce a certain induction decreases with increase in temperature while for high inductions it increases. The materials examined by these investigators include soft iron, mild steel, hard steel, electrolytic iron, and nickel. Ewing 5