64 ELECTRICAL ENGINEERING PROBLEMS 



If the frequency is 60 and the motor is taking 16 amperes, required 

 the currents in the other two circuits, the whole current and its 

 power factor and the necessary e.m.f. (10 raw.) 



42. Two parallel circuits have resistances of 20 and 30 ohms 

 and reactances of 10 and 40; find the e.m.f. necessary to give a 

 combined current of 100 and how this current divides between the 

 circuits. (8 ram.) 



43. The load on a transformer is made up of 500, 200-ohm 

 incandescent lamps and an induction motor circuit having an 

 equivalent resistance of 0.25 and a power factor of 70.7%. The 

 current is 500. Find the e.m.f., the current in each circuit and 

 the power factor of the system. (9 ram.) 



44. The resistance of two circuits in parallel are 16 and 20 ohms 

 and their inductances 0.08 and 0.12 henries; the frequency is 80; 

 required the e.m.f. necessary for a total current of 10 amperes. 

 (9 ram.) 



45. Three parallel inductive circuits of 3 ohms resistance each 

 have power factors of 0.2, 0.4 and 1. The total current is 200 

 amperes. Required the e.m.f. and. power factor of the current. 

 (4 ram.) 



46. Two induction motors are run on the same circuit and take 

 together 400 amperes with a power factor of 0.75; one motor has 

 a power factor of 0.70 and an equivalent resistance of 0.8; the 

 current taken by the other is 250. Find the e.m.f. and the other 

 current; also the other power factor. (5 ram.) 



47. If the 3 circuits of problem 6 are placed in parallel and the 

 combined current is 50 amperes, find the e.m.f. and the power 

 factor of the system. (8 ram.) 



48. Four parallel circuits have resistances of 20, 10, x and 1, 

 and inductances of 0, 0.025, 0.12 and y; the e.m.f. is 200, perio- 

 dicity, 90, and the currents in the third and fourth circuits, 2.6 and 

 1.6. Find the currents in the first and second, the total current 

 and its lag, and the equivalent resistance and inductance for the 

 whole circuit. (10 ram.) 



49. Two parallel circuits have 0.2 and 0.03 henries and and 10 

 ohms respectively; a circuit in series with them has 0.05 henry and 

 8 ohms; the current through the 10-ohm circuit is 3 amperes at 

 60 periods; required the e.m.f. around each circuit and around the 

 whole; also the two unknown currents and the lag for the system 

 as a whole. (10 ram.) 



