222 ELECTRICAL MACHINERY 



per second. Even a low voltage across this condenser 

 would produce a very large charging current. 



54. Current in Circuits Containing Resistance, Induct- 

 ance, and Capacity. Series Circuit. Let us consider a 

 circuit made up of an inductance, resistance and capacity 

 all in series arranged as in Fig. 133. 



Let / = the current in the circuit; 



E = the voltage impressed on the circuit; 

 R = the effective resistance of the circuit; 

 L = the coefficient of self-induction in henries; 

 C = the capacity of the condenser in farads; 

 /=the frequency of the voltage. 



L R C 



zXxxRftT v/wwwv r=i 



Ammeter 



A.C. Supply 

 of Voltage = E 



FIG. 133. Circuit Containing Inductance, Resistance and Capacity 



in Series. 



The three reactions which the current sets up in the 

 circuit are: 



Resistance reaction =IR, opposite in phase to the current; 

 Inductance reaction = 2x/L7, 90 behind the current; 



Capacity reaction = S-TF 90 ahead of the current. 



The sum of these three reactions must be equal and 

 opposite to the impressed force, E. The three reactions 

 are plotted in Fig. 134 as OB, OC, and OA respectively 

 and their resultant is found to be OE, The impressed 



