120 Prof. T. K. Lyle on the Variations of 



appear as 3rd, 5th, &c, harmonics in the magnetizing current, 

 and would he greater as the impedances of the primary 

 circuit for currents of these different periods were less, if we 

 assume that the amplitudes of the upper harmonics of the 

 flux are fixed. 



Now in order to ohtain the larger magnetizing currents it 

 was necessary to reduce the impedance, and hence in these 

 cases the higher harmonics produced as ahove by the reaction 

 of the ring became greater and the magnetizing current 

 more distorted. Also in order to get the slower speeds 

 fewer cells were used to supply current to the rotary con- 

 verter, thus reducing the applied E.M.F., and in order to get 

 the same currents as before the impedances used had to be 

 proportionally reduced. Hence, in the slower speeds the 

 upper harmonics of the current due to the reaction of the 

 ring would be relatively greater and the distortion of its 

 wave-form more marked. 



This phenomenon is an interesting case of transformation 

 and what may be called reflexion of energy. Thus the iron 

 receives energy from the first harmonic (frequency n) of the 

 exciting current, some of which it transforms to vibratory 

 energy of • frequencies 3n, 5n, &c. ; and sends back energy to 

 the primary circuit by means of currents of these higher 

 frequencies, where in general this reflected energy will be 

 dissipated as heat. 



This reflexion of energy occurred in nearly all the ex- 

 periments recorded in this paper, and the amount in each 

 case for each harmonic is obtained when calculating the iron 

 loss by the analytical method given in § 7. 



Thus the energy D received per cycle by the iron and 

 dissipated as heat in it is given by 



Jo dt 



= D X }-D 3 + D 5 + &c. (say). 



where C„ C\, C 6 , F 1} F 3 , F 5 are the 1st, 3rd, and oil 

 harmonics of current and flux respectively. 

 Now if, for instance, 



D, or n ( T G^dt 



Vo dt 



is negative, the iron by means of the third harmonics is 



