114 



EFFECT OF CAPACITY. 



in this case the voltmeter was of the dynamometer 

 pattern, and the switches are arranged so that its current 

 does not pass through the ammeter, as its amount would 

 not be negligible compared with the small current in the 

 circuit. 



The non-inductive resistance R was a, bank of lamps ; 

 the condenser had a capacity of 20 microfarads. The 

 periodicity was 54 per second. 



Determination of Power in Circuit with Capacity. 



Capacity and Self-induction in Series. It has been shown that 

 the effect of self-induction in a circuit is to cause the 

 current to lag in phase behind the voltage, and that a 

 capacity causes the current to lead in phase. When both 

 capacity and self-induction are present, the effect is to 

 produce a difference of phase between current and voltage, 

 which is the difference between the angle of lag or lead, 

 which would be due to either acting separately. 



This result is best shown in diagram form by drawing a 

 line C to represent the current horizontally (see Fig. 54). 

 The energy voltage spent in overcoming the non- 

 inductive resistance of the circuit ( = C x R) and the iron 

 losses is then marked off as the length E z to the scale of 

 volts. At E 2 the line E 2 E l is drawn vertically upwards 

 to represent the volts spent in overcoming the capacity 



/ C \ 

 of the circuit ( = ^). From E l the length E l E 3 is 



measured downwards to represent the voltage overcoming 

 self-induction ( = 2*91 LC). The triangle OE.,E 3 then 

 represents the following quantities, viz. : The total voltage 

 E 3 , the resultant idle voltage E 2 E 3 , and the energy 



