Iron under Small Periodic Magnetizing Forces, 247 



shows strikingly the effect of the value of on the iron loss, 

 In the upper figure the one curve is for the highest induction 

 (B max = 563) , where the value of 6 was 14°-97 : the other (for 

 which each of the scales is 20 times that of the first) is for 

 B m ax. = 14*9, the corresponding value of 6 being 260. In 

 the lower figure the values are B ma3: . = 440, = 43°' 62, and 

 B max =12'9, = 12°'4O. The marked effect of the eddy 

 currents is seen by comparing the two curves A (for which 

 the value of H ma5 . is the same) , and also the two curves B, 

 with one another. 



7. The main results obtained in this paper are as follows,, 

 the value of the induction being below 600. 



In a specimen in which eddy-currents were very small : — 



(1) jjlq diminishes with B 1? and tends to a finite A'alue for 

 very small values of B 1? which for the specimen was about 

 157. For a considerable range at the lower inductions ^ 

 can be represented closely as a linear function of H^. 



(2) 6 diminishes rapidly as B x diminishes, and tends to a 

 very small limiting value for very low values of the induction. 



(3) b 3 decreases slowly as B x diminishes, and approaches a 

 value about *030 for the weakest fields used. 



(4) i/r 3 gradually increases as the induction decreases and 

 tends to a value of about 60° for exceeding low values of B x . 



(5) Change of frequency has practically no influence on 

 fiQ and 6. 



(6) The hysteresis loss was practically independent of the 

 frequency, and so the loss due to kinetic hysteresis was too 

 small to detect with certainty. 



(7) Steinmetz's coefficient a decreases rapidly as the 

 induction is decreased, and has a value not very different 

 from zero for very low values of B lt 



In a specimen in which eddy currents were considerable, 



(1) fx diminishes with B x and tends to a finite value for 

 very small values of B x for any particular frequency. The 

 value for slow speeds was about 156. 



(2) For a limited range at low inductions, /jl can be repre- 

 sented closely as a linear function of H^. 



(3) 6 diminishes as B x diminishes, and tends to a definite 

 limiting value at very low values of the induction for each 

 particular frequency. 



(4) The limiting values of yit and 6 are consistent with the 

 assumption that the induction at any point is in phase with 

 the magnetic intensity at that point. 



(5) b 3 is fairly constant for any particular frequency, its 

 value diminishing as the frequency is increased. 



