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



As in the preceding case the temperature was kept as con- 

 stant as was possible while the magnetic force was varied and 



Fig. 8. 



16000 

 14000 

 12000 

 10000 

 W 8000 

 6000 

 4000 

 2000 











— IRON — 



Tl/NGST£ 



Alloy 





































20 H 30 



the observations repeated several times with reversed direction 

 of magnetizing currents. For most of the temperatures 

 given the whole set of readings were repeated. 



It has been mentioned above that the process of " demag- 

 netizing by reversals " does not appear entirely to wipe out 

 all the effects of previous magnetization, although the effect 

 of residual magnetism is noticeable under extremefy small 

 magnetic forces only at very high temperatures when the 

 metal is in a critical state. With the tungsten alloy this 

 residual effect could not be detected, even at the highest 

 temperature. 



Fig. 9 shows the permeability-temperature curves for 

 different magnetizing forces, plotted from the following 

 data: — 



Temperature 



ju for 



fi for 



/j, for 



fi for 



in Degrees 



H = 14-885. 



H=8-156. 



H= 4-078. 



H =2-039. 



0. 



(Curve I.) 



(Curve II.) 



(Curve III.) 



(Curve IV.) 



o 

 15 



647 



176 



130 



117 



266 



686 



557 



168 



140 



370 



660 



847 



292 



219 



468 



647 



987 



649 



304 



543 



622 



1028 



1396 



693 



591 



609 



1028 



1615 



996 



632 



557 



942 



1645 



1775 



640 



513 



887 



1535 





649 



442 



788 



1436 



2121 



655 







1386 



2143 



660 



lis 



168 



227 



308 



