ELECTRIC CIRCUITS 



133 



(3) The impedance of a circuit includes both the resistance and 



the reactance; it is 



2 _ impressed e.m.f. 

 current 



(4) The admittance of a circuit is 



current 





impressed e.m.f. 

 it is the reciprocal of the impedance and thus 



Y = -= 



z 



+ 



(180) 

 (181) 

 (182) 



The admittance has two components, conductance and sus- 

 ceptance. 



Fig. 101 shows a circuit of impedance Z = VR 2 + X 2 in 

 which the current lags behind the impressed e.m.f. by an angle 





FIG. 101. 



<. The current I can be resolved into two components in phase 

 and in quadrature with the impressed e.m.f. E. The in-phase or 

 power component of current is 



where 







is the conductance of the circuit. 



The quadrature or wattless component of current is 



where 



X 



B = = 



X 



R2 



is the susceptance of the circuit. 



(183) 



(184) 



(185) 

 (186) 



