110 



Potts — Rowland' 's New Method. 



III. Hysteresis. 



The arrangement used for the determination of losses of 

 energy due to hysteresis and Foucault currents is the same as 



for the determination of 

 electric absorption, with 

 several additional ele- 

 ments. 



Fig. 8 shows the 

 arrangement used. All 

 the arms are the same as 

 in fig. 2 except arm 1. 

 Arm 1 contains a coil 

 L. In this coil is placed 

 the iron to be tested, F. 

 I is a small coil of wire 

 surrounding the iron, 

 and used to determine 

 the induction through 

 the iron. The two coils 

 of the electro-dynamom- 

 eter D 2 are connected in 

 series. The key K a 

 serves to put the coil /, 

 the resistance r 3 and the 

 coils of the electro- 

 dynamometer in series. 

 By noting the deflection 

 produced by the current 

 induced in I, the induc- 

 tion may be calculated, 

 the electro - dynamom- 

 eter having been previ- 

 ously calibrated. 



R s is a small resist- 

 ance in arm 1. A small current is shunted off from the termi- 

 nals of R s and can be sent through the resistance r„ and the 

 electro-dynamometer by the key K 4 ; and thus the total current 

 in arm 1 may be determined. 



Measurement of the current. — The calibration of the electro- 

 dynamometer showed the current to be quite accurately pro- 

 portional to the square root of the deflection (<y/rT). A deflec- 

 tion of 1 cm. corresponds to a current of '00213 ampere. We 

 shall then have the total current in arm 1 



C 1= = '00213^ ^=- s 



