POWER AND POWER-FACTOR. 75 



The currents are shown in Fig. 34 both in the form of 

 curves and in the form of vectors, in which N, N C 

 are the two components of C, which represents the total 

 current. 



As in the previous discussion, it is only the current 

 and voltage which are coincident in phase which 

 represent power given to the circuit. Hence in this case 

 power of circuit = energy current X total voltage. 



= C cos <t> X y = C V cos as before. 



Actually the two points of view illustrated by Figs. 7 

 and 34 lead to the same result, the difference lying in this, 

 that in one case we speak of an idle component of the 

 voltage overcoming the effects of self-induction, whereas 

 in the other case we speak of an idle current, which may 

 also be termed the magnetising current, and which is 

 the portion of the total current spent in producing the 

 magnetic field which is the manifestation of the self- 

 induction. 



The following experiment is given as an example of 

 this method of regarding the quantities in the circuit, 

 and should be carefully compared with Experiment VIII. 

 The measurements are a repetition of those made in 

 Experiment VIII., but the conclusions drawn from them 

 are obtained by a different course of reasoning. 



EXPERIMENT XII. DETERMINATION OF IDLE AND 

 ENERGY CURRENT IN A CIRCUIT. 



DIAGRAM OF CONNECTIONS. 



R r 



AAAAA ^WtflT- ' 



FIG. 35, 



Source of alternating current. 



Wattmeter. 



Non-inductive resistance. 



Inductive resistance. 



Ammeter measuring current of circuit. 



Voltmeter ,, voltage ,, 



Switch for breaking circuit. 



