128 ELECTRICAL ENGINEERING 



leading the impressed e.m.f. by an angle <, where 

 tan *=^f^- 2 = ^ = 0.46, 



1 O 



and therefore 



< = 24 42'. 



If the e.m.f. impressed on the circuit is maintained constant 

 and the frequency is varied find the magnitude of the main cur- 

 rent when it is in phase with the e.m.f. 



The current at any frequency is 



(7 2 - 7 3 ) 



X~YJ 



the angle of lag of the current behind the e.m.f. is 

 ../.-ft ,_. l/X - l/X, 



<t>= 



When the current is in phase with the e.m.f. 



< = and X = X c or 2irfL = ^ 



the frequency is therefore 



The main current at a frequency of 50 cycles is 



E 200 

 7 = /i=^=^- = 5 amperes; 



the current in the inductive reactance is 



72 = I - 2 X 3.14 2 X50 X 0.1 - 6 " 36 amperes; 

 the current in the condensive reactance is 



h = v- = - ; - = 6.36 amperes; 



.A. 1 



2 X 3.14 X 50 X 10- 4 



