EFFECT OF CAPACITY. 



123 



Tj and T. 2 no current will apparently pass from one to the 

 other. This condition could, of course, only exist when 

 both branches are without resistance and sources of loss, 

 such as hysteresis or eddy currents. 



Example. As an example of what has just been said 

 may be quoted an experiment of Mr. W. N. Mordey.* 



FIG. 58. INDUCTIVE RESISTANCE NEUTRALISING IDLE CURRENT DUE TO 

 CAPACITY OF CABLE. 



Mr. Mordey connected an alternator giving 2,050 

 volts at 100 cycles to a 5^-mile length of 37/15 concentric 

 rubber-covered cable, one pole of the alternator being 

 connected to the inner core and the other pole to the 

 outer core, which was earthed, as was also the steel 

 sheathing. 



The capacity of the cable between conductors was '86 

 microfarad per mile, thus the virtual current taken from 

 the alternator was calculated to be 



.C = 2 7T71 E K = 



2 TT x 100 x 2,050 x -86 x 5-5 



1,000,000 

 = 6-092 amps. 



The current actually observed was 6 amps. A choking 

 coil was then put in a circuit connected to the alternator 

 in parallel with the cable. The connections were then as 

 shown in Fig. 58. The coil was so designed that with 

 switch Si open and $ 2 closed, so that the alternator sup- 

 plied current to the coil only, the current taken by the 

 coil was 6 amps. 



On closing both switches, so that the alternator sup- 

 plied the two circuits in parallel, the current given out by 

 the alternator was found to fall to 1*6 amps. Thus 

 ammeters A l and A. 2 both indicated 6 amps., while A 3 only 

 registered 1*6 amps. 



* Proc. Inst. Elec. Eng., vol. xxx., p. 378. 



