Hence 



SINGLE-PHASE CURRENTS. 



W El X power factor = El cos 6. 



cos 6 = power f actor = W -f- 7. 



[Exp. 



The angle is thus computed from the readings of the wattmeter, 

 voltmeter and ammeter. 



In constructing Fig. 7, lay off OA = E ; then lay off OD = I, 

 at an angle 6 determined as above, and construct the right tri- 

 angle of electromotive forces, OCA. 



Adjusting 

 Jtesist&nco 



FIG. 6. 



Circuit containing coil R 2 L 2 . 



Compute the components of electromotive force and current, 

 and verify the various relations discussed in the following 

 paragraphs. 



39. Components of Electromotive Force. In the manner just 

 described, the electromotive force is resolved into the power com- 

 ponent, Ep = OC, in phase with I, and the wattless component, 

 EQ CA, in quadrature with /. These components are 



P = E cos E X power factor ; 

 EQ= sm6 = E X reactive factor.* 



The vector sum of these two components gives the total im- 

 pressed electromotive force. 



* (39a). Designating power factor by p and reactive factor by q, it is 

 seen that j>* + q 2 =i. Compare Standardization Rule 56. 



