332 proceedings of the american academy. 



Examination of the Oscillograms with the Aid of the Theory 



of Alternating Currents. 



The so-called " voltage-phase cycle " gives the instantaneous values of 

 the current through the deflecting coils and through a resistance chosen 

 to make the amplitude of this current the same as the amplitude of 

 one loop of the current through the rectifier, under the same applied 

 voltage. Although the current of the voltage-phase cycle lags behind 

 the externally applied voltage by an amount depending on the relation 

 of the self-inductance of the deflecting coils to the resistance of the cir- 

 cuit, the current is nevertheless in phase with the voltage immediately 

 about the substituted resistance ; for the voltage about a resistance is 

 in phase with the current through it. Now by throwing the switch at T 

 of Figure 6, we put the rectifier in the circuit in the place of the resist- 

 ance. If the rectifier, when current traverses it, introduces into the 

 circuit electromotive forces out of phase with the current through it, 

 we ought to get a shift of phase of the cycle. We can easily see, for 

 example, that if the rectifier contained capacity or inductance, such a 

 shift would occur. Also, if the action of the rectifier were one of elec- 

 trolytic polarization, the back e. m. f. of polarization would be approxi- 

 mately determined at any part of the cycle by a time integral of the 

 current, and would introduce a shift of phase resembling that intro- 

 duced by a capacity. 13 



Also, if the action of the rectifier were due to thermoelectricity, we 

 should expect the thermoelectromotive forces developed to be of the 

 form 



(1) ± a I frdt, 



due to the Joulean heat at the high resistance, and of the form 



(2) ± b Cidt, 



due to the Peltier effect at the junctions. To these terms we should 

 have to add also terms taking account of conduction of heat from the 

 junctions. The term for the conduction of heat would be difficult to 

 assign definite values, but it would be functions of the rise of temper- 

 ature of the junctions, and may be written in the general form 



13 B. 0. Peirce : Newtonian Potential Function, p. 323 Boston, 1902. 



