ELECTRIC CIRCUITS 



121 



and 



z = 



+ (x - x c ) 



where L is the inductance of the circuit in henrys, C is the capacity 

 in farads and / is the frequency of the impressed e.m.f . 

 The angle of phase difference between the e.m.f. and current is 



$, where 



# 2 - # 3 I(X-X C ) X-X C 



tan 



IR 



R 



FIG. 92. 



and 



If X > X c the current lags behind the e.m.f. ; 



if X = X c the current is in phase with the e.m.f.; 



if X < X? the current leads the e.m.f. 



(7) An alternating e.m.f. E is impressed on the terminals of 

 the circuit in Fig. 92 consisting of a resistance R and an inductive 

 reactance X in parallel. 



