13 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



for some time because the magnetizing field is less than that due to 

 the coil current by that due to the eddy currents. If, therefore, from 

 the numbers of Tables I and II we were to determine the form of a 

 current curve for Q, corresponding to any journey of the core, this 

 would fall somewhat below the actual curve at the beginning. The 

 core of Q has, however, a typical magnetizing diagram, and the theo- 

 retical curves are instructive as showing what the actual curves would 

 be if the same core were more finely divided. The effect of eddy cur- 

 rents can be seen in the curves for this magnet given above. 



CURRENT. 



-SLOPES 



X 



Figure 31. 



Magnetization curve for the core of the magnet Q which at the outset is in a 

 neutral state. The ordinates of tlie clotted curve represent twice the slopes of 

 the other curve. 



The boundary of the shaded area in Figure 32 shows twice the value 



of the integrand 



13.94\ 



w = 



E — ri 



(20) 



for the case E = 26, r = 20 : the horizontal unit is one tenth of an 

 ampere. The vertical line corresponding to / = 1.3 is evidently an 

 asymptote. The area under the curve from the beginning to the ordi- 



