EFFECT OF CAPACITY. 



105 



Obviously the readings taken would enable us to determine 

 the power of the circuit, since we have determined the total 

 current and voltage, and also the power factor of the circuit. 

 The total power = amperes x volts x power factor. 



V3 

 SCALE: or VOLTS 



10 20 30 40 50 60 70 80 90 100 110 120 

 FIG. 47. DIAGRAM OF VOLTS FOK CIRCUIT, WITH CAPACITY. 



The calculation might also be carried out as in the 

 Experiment XIII. by the 3-voltmeter method. 



This calculation was carried out for all the readings of the 

 series from which the readings in the table above were taken 

 At the same time the power was measured on a wattmeter, 

 and except in the case of the first reading, where the power 

 factor is very low, the results of the calculation agreed with 

 the readings of the wattmeter within a fraction of 1 per cent. 



The idle and energy currents in the circuit might be cal- 

 culated from the readings taken in the last experiment, 

 since idle current = C sin <f> , and energy current = C cos 0. 



Instances of circuits containing sufficiently large 

 capacities to seriously affect the nature of the current 

 chiefly arise where long feeders have to transmit current 

 to a considerable distance. Instances of a current which 

 leads the voltage in phase from other causes are, 

 however, not at all infrequent, and will be referred to 

 later in connection with the running of synchronous 

 motors. 



