INDUCTIVE CIRCUITS IN &Eltll-:x AND I'M; M.I. 1. 1. 61 



will be the e.m.f. on this circuit? What per < -nt \\ill the drop in 

 the line, from no load to full load !>, <>! thi> .m.i'.'.' ; //-//i.) 



17. A machine takes 30 volts and 12 amperes; required the 

 inductive e.m.f. of a choke coil to be placed in scries with it 6n a 

 100-volt circuit, if the resistance of the choke coil and the induc- 

 tance of the machine be negligible. (3 rain.) 



18. A soldering iron built for 50 volts and 3 amperes is to be 

 used on a 100-volt, 60-period circuit, with a choke coil. If the 

 resistance of the choke coil is 1 ohm, required the e.m.f. around 

 the choke coil, the inductive e.m.f. and the inductance. (.; , 



19. Required the inductive e.m.f. to be given by a 0.2-ohm 

 choke coil so that the e.m.f. of a circuit may be cut from 100 to 

 40 volts, for a 10-ampere current. What is the power factor and 

 the efficiency? (4 raw.) 



20. Required the e.m.f. around a 3-ohm choke coil to be used 

 in series with a 50-volt, 25-candle-power lamp, taking 1 watt per 

 candle-power for use on a 110-volt circuit. Required also the 

 efficiency. (4 min.) 



21. A motor takes 50 amperes, lagging 30 degrees. It is fed 

 through a circuit of 1 ohm resistance; what must be the generator 

 e.m.f. to give 1000 volts at tne motor? What is the drop at the 

 motor terminals from no load to full load? (3 min.) 



22. Two circuits are connected in series upon a 200-volt e.m.f. 

 The resistance and reactance of the first are 0.50 and 0.75 ohms, 

 and a current of 20 amperes lagging 30 degrees behind the e.m.f. 

 of the second circuit is flowing; required the e.m.f. 's on both 

 circuits. (This problem is used on transformer work. The first 

 circuit is the transformer secondary, the second the load.) (4 / 



23. The secondary coil of a transformer and the circuit which it 

 supplies are in series. The e.m.f. impressed upon the secondary 

 is 200 volts, and its resistance and reactance are 0.2 and 0.5 ohms. 

 The current is 50 amperes, and lags 30 degrees behind the terminal 

 e.m.f. of the transformer. Required the voltage on the load and 

 the impedance drop in the secondary. (S min.) 



24. An induction motor taking 5000 kilowatts at 10,000 volts 

 and 85% power factor is supplied through a line having a resist- 

 ance of 1.2 ohms, and a reactance of 0.3 ohm. What must be the 

 generator e.m.f. ; also the drop in volts at the motor from no load 

 to full load; and the regulation, that is, the per cent which the 

 above drop is of the full-load voltage. (6 min.) 



