14 Mr. R. L. Wills on the Effects of Temperature 



maximum permeability occurs has been taken, and the results 

 shown graphically in fig. 7, where the ordinates to the curve 

 measure the magnetizing forces giving the maximum permea- 

 bility and the abscissae the corresponding temperatures. 



The curve in the figure gives a measure of how much 

 earlier in the magnetizing process the successive stages are 

 brought on by heating to any temperature; and it will be 

 seen that the rate of transition from stage to stage increases 

 with the temperature. 



Fi-. 7. 



Ph 



3 



?-'?5 





















2'00 

 1-75 

 1-50 

 V85 







































1-00 

 0-75 





















0-50 

 0-25 



































\ 





100° 200° 300° 400° 500° 600. 



Temperature in Degrees Centigrade. 



700° 



It has been shown above that the rise in permeability as 

 the second stage is entered upon becomes more rapid as the 

 magnetizing force is reduced ; under a force of 1*075 C.G.s. 

 (fig. 3) the permeability increases comparatively gradually 

 as the temperature is raised ; while with a force of 0*172 c.G.s. 

 (fig. 4.) the permeability rises very rapidly when the second 

 stage is brought on. This is explained by the rate of tran^ 

 sition from stage to stage being much greater at high than at 

 low temperatures ; in the former case the second stage is just 

 entered upon while the ring is cold, while under the smaller 

 magnetizing force the temperature necessary to bring on this 

 stage is about 650° 0. 



Tungsten Alloy, 



In the case of iron and highly permeable substances the 

 first and second stages of the magnetizing process extend 

 over a comparatively small range of magnetic force, and the 

 passage from one stage to the other at high temperatures 



