Pupin — Resonance Analysis of Alternating Currents. 383 



When quantitatively very accurate results are desired then a 

 low resistance, say one ohm, should be used for the section ao 

 and an electrometer capable of giving a large deflection for ten 

 volts. 



The principal interest, however, in the study of the disto?*- 

 tlon of alternating current waves, is centered not so much in 

 the exact ratio of the amplitudes of these harmonics to the 

 amplitude of the fundamental wave, as it is in the causes pro- 

 ducing these harmonics and the conditions which modify the 

 effects of these causes. Hence a quantitatively less accurate 

 arrangement will do, provided that it is very sensitive, simple, 

 and easily manageable. Such an arrangement is given, fig. l b . 



It differs from that given in fig. l a in the substitution of an 

 air core transformer coil a'V for the non-self-inductive resist- 

 ance ah. The secondary of this coil forms a part of the 

 resonator circuit. For every harmonic of the inducing current 

 we shall have a harmonic electromotive force of the same fre- 

 quency in the resonant circuit. By varying the capacity in the 

 resonator and watching the voltmeter needle, we can tell by 

 the deflection of the needle, whenever we have reached the 

 capacity which with the self-induction of the resonator brings 

 this circuit into resonance with one of the harmonics. A refer- 

 ence to fig. 2 will explain this more clearly. 



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In this figure the lower horizontal row of figures refers to the 

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