60 ELECTRICAL ENGINEERING PROBLEMS 



a drop of 1000 volts around A; required the drops around B and 

 C in series and A, B and C in series. (7 ram.) 



8. Two circuits in series have resistances of 10 ohms each, one 

 has 10 ohms reactance and the e.m.f. across the other is 15; with 

 1 ampere flowing, find the impressed e.m.f. and the reactance of 

 the other circuit. (5 ram.) 



9. Two circuits in series have reactances of 2 and 4 ohms, the 

 first has 3 ohms resistance; if 50 amperes flow when the circuits 

 are placed on a 400-volt circuit, required the value of the other 

 resistances. (5 ram.) 



10. Given two circuits in series, one of 10 ohms resistance and 

 the other of 0.1 henry inductance; required the current if E be 

 1000 and co, 600. Also if the first circuit be cut out. (4 ram.) 



11. The secondary of a transformer and the load it supplies 

 with current are in series. The e.m.f. kaprisse&-en the secondary 

 is 100 and its resistance and reactance are 0.02 and 0.085 ohms. 

 The current is 150 amperes, lagging 45 degrees behind the impressed 

 e.m.f. Required the voltage on the load and its power factor. 

 (5 ram.) 



12. For three circuits in series the resistances are 100, 75 and 

 30 and the inductances 1, 0.3 and 0; the frequency is 60; required 

 the lag for each circuit and for the system; also the power factor 

 for the system. (10 ram.) f 



13. A 50-volt incandescent lamp taking J ampere is placed on 

 a 100-volt circuit; what must be the value of L in a choke coil 

 placed in series with this lamp to give the right voltage, if the 

 resistance of the coil be negligible and if the frequency be 1|)0? 

 What will be the lag, the power factor and the efficiency of the 

 combination? (5 ram.) 



14. The resistances of three circuits in series are 12, 8 and 5 

 ohms; the inductances of the first two are 0.1 and 0.15, and the 

 tangent of the angle of lag of the third is J, CD is 200. "With 20 

 amperes flowing through the circuit, find the e.m.f. between the 

 terminals. (5 ram.) 



15. A choke coil to turn down a 55-watt, 110-volt lamp, 

 reducing the pressure to 50 and 25 volts, is to be designed. What 

 must be the inductive e.m.f. 's, neglecting the resistances of the 

 coil? Required also the power factors. (7 ram.) 



16. A circuit having r, 5, and x, 2, is fed by a transmission line 

 of 1 ohm resistance. With a generator e.m.f. of 1000 volts, what 



