Use of Mutual Inductometers. 



507 



or yi^a-itan 2 ^) 



Usually </> is so small that we may take 

 1,/1,-S/Q. . . . 



(27) 



Fin. 4. 



© 



With regard to the actual working of the method, the 

 inductometer should be a low-reading one whose primary 

 coils can carry the large primary current. The resistance 

 Q, may be a standard low resistance shunted by a slide wire 

 along which the slider runs. Tests by this method on a 

 commercial transformer gave results in practical agreement 

 with those obtained by Sir. C. C. Paterson by a wattmeter 

 method, the source of current being a sine-wave alternator. 

 This agreement is interesting as showing that the harmonics 

 in the secondary current (which are not taken account of by 

 the vibration galvanometer) have very slight effect on the 

 results. The method should only be used where the primary 

 current can be made approximately sinoidal. 



In conclusion. I would express my best thanks to 

 Dr. Glazebrook for his kind interest in the work, and to 

 Mr. T. L. Eckersley for valued and suggestive criticism. 



