Temperature on the Hysteresis Loss in Iron. 



129 



ordinary temperatures, but the later experiments of Roget* 

 deal with temperatures ranging from 50° C. to 700° C In 

 these experiments the specimens were, however, removed 

 from the oven, and the tests then made at ordinary atmo- 

 spheric temperature. It appeared desirable to examine the 

 effects produced by prolonged heating when the temperature 

 is maintained constant and the specimen is not cooled for the 

 hysteresis measurement. 



Roget continued the heating at the lower temperatures for 

 about a month and found that below 135° C. the hysteresis, 

 for an induction of 4000, during this time increased, at first 

 rapidly, but more and more slowly as time went on. For 

 higher temperatures the hysteresis for the given induction 

 reached a maximum value after a time depending on the 

 temperatures. Then, as the heating was continued, the 

 hysteresis fell, the rate of fall being greater for high than 

 for low temperatures. 



In the present series of experiments the specimen was first 

 annealed and then the hysteresis for different ranges of in- 

 duction measured at intervals, while the temperature was 

 kept as nearly constant as was practicable. 



The curves II. III. IV. (fig. 6) show the results of tests 







Fig. 6. 







6000 









■ i 











/ 



// y 



i 



2000 







A 



// 







■ , 



-y/ _^ 







2000 4-QOO fiOOO 8000 100.00 



6 



made at a temperature of 165° C, after continued heating 

 for 16, 41, and 84 hours respectively; the curve I. gives the 

 initial values of the hysteresis at the same temperature. For 

 longer periods of heating at this temperature the hysteresis 

 remained practically constant. After this constant condition 

 Avas reached by prolonged exposure to any temperature, the 

 hysteresis measured at that temperature was practically the 

 same as its value after the specimen had been cooled to 



• Ibid. vol. lxiii. pp. 258-267 (1898), and vol. lxiv. pp. 150-156 (1898). 

 Phil. Mag. S. 6. Vol. 5. No. 25. Jan. 1903. K 



