INDUCTIVE CIRCUITS IN SERIES AND PARALLEL 63 



33. On a 10-ampere circuit is to be placed a group of five 1- 

 ampere, 50-volt lamps in parallel. To by-pass the remainder of 

 the current a choke coil (resistance negligible) is to be used in 

 parallel with the lamps. For what current must this coil be 

 designed? (3 min.) 



34. Two circuits in parallel have respectively n = 12; tan <h = 

 1.25; r 2 = 30; and L 2 = 0.015. What will be the angle of lag of 

 the resultant current and what will be its value if E be 117 volts 

 and co be 500? (8 min.) 



35. Two parallel circuits on a 5000-volt system have resistances 

 of 20 and 50; also the power factor of the first is 0.447, and a 

 current of 40 amperes flows in the second circuit; required the 

 reactance of this circuit and the total combined current. (8 min.) 



36. Two motors are running in parallel on a 500-volt gystem. 

 One has an equivalent resistance of 5 and a power factor of 89.4%. 

 The combined current is 110 amperes and lags 30 degrees. Find 

 the current in each motor and the power factor of the second 

 motor. (5 min.} 



37. If the two circuits of problem 1 are placed in parallel on a 

 220-volt circuit, and the first circuit takes 25 amperes, determine 

 the frequency and the current in the other circuit. (7 // 



38. Using the notation of problem 3, but with the circuits in 

 parallel and carrying currents Ii and I 2 , draw the diagram and state 

 the solution for six cases as follows: To find Xi, x 2 , I; r*, \i, I; 

 r 2 , xi, x 2 ; E, I lf I 2 ; E, I, I 2 ; E, Xi, x 2 . (20 min.) 



39. An induction motor taking 10 amperes with a power factor 

 of 86.6% is placed on the same line with 30 incandescent lamps, 

 in parallel, each taking \ ampere; find the current in the line. 

 Required also the power factor. (3 min.) 



40. A projection lamp taking 15 amperes at 40 volts and with 

 a power factor of 85% is to be used in parallel with a load of lamps 

 on a 110-volt system. Compare the currents in the feeder with 

 a transformer and with a choke coil used to reduce the e.m.f. 

 (a) With 200 J-ampere lamps in parallel, (b) With 20 J-ampere 

 lamps in parallel. Which would you use, transformer or coil? 



(7 min.) 



41. On a certain circuit are an induction motor, synchronous 

 converter and a load of incandescent lamps. The motor has 

 equivalent resistance and inductance of 5 and 0.01, the con\ 



3 and 0.015, while the combined resistance of the lamps is 6.25. 



