24:2 Behaviour of Iron under Small Magnetizing Forces. 



values of b- and fa for the lower inductions. This arises 

 from the small value of b 5 . The amplitude of the galvano- 

 meter deflexion was seldom more than 20 mm., so that if b$ 

 were "01, the amplitude of the fifth harmonic would be only 

 "2 mm., and a slight unsteadiness of the readings from any 

 cause might greatly affect the values of both b 5 and i|r 5 . 



In fig. 2 (lower curve) the hysteresis loss is plotted against 

 the maximum value of B for the different experiments of 

 the four series. To avoid confusion, several points at the 

 lower inductions have been omitted, but in every case all 

 points that have been left out lie on the curve. It is seen 

 that here again the four series of points lie on practically the 

 same curve ; that is, the hysteresis loss for the specimen under 

 examination is practically independent of the frequency, pro- 

 vided the maximum induction does not exceed 600. This 

 being the case, it would be impossible with the present 

 apparatus to detect with certainty a loss due to kinetic 

 hysteresis at these low inductions. 



On the same diagram (fig. 2, upper curve) is shown 

 the variation of Steinmetz's coefficient a * (I = a^B v6 ), with 

 the maximum value of the induction. The curves show that 

 or decreases rapidly as the induction dirninishes, tending 

 towards the value zero at very low inductions. Further, a 

 increases with frequency, the increase being due to the 

 increased eddy-current loss, for if the eddy-current loss is 

 deducted, the points all lie on one curve. 



6. A further series of experiments was performed on a 

 long rod of Lowmoor iron 0'3 sq. cm. in cross section, in 

 which the eddy-current effect would be considerable. As 

 for the former specimen, four different frequencies were 

 employed, namely, 55, 28, 15, and 8*5. 



Details of Loivmoor Iron Rod. 

 A straight cylindrical rod of circular section. 



Area of section *2999 sq. cm. 



Length 360 cm. 



Specific resistance at 12°'5 C... 1-119 X 10 4 . 

 Number of turns on central coil. 100. 

 Magnetizing solenoid as before. 



The results obtained with this specimen are given in 

 Tables V. to VIII. 



*. In calculating a, the effective induction 35 has been used, not the 

 maximum induction Bmar. 



