CHAPTER VI 

 CAPACITY AND INDUCTIVE CIRCUITS, RESONANCE 



1. A 200-microfarad condenser is connected through a resist- 

 ance of 50 ohms to a 100-volt circuit having co = 400 (frequency 

 63.7). Construct the triangle and determine the current and 

 power factor. (2 min.) 



2. The same condenser is connected through a resistance of 

 2 ohms to a 1000-volt circuit of the same frequency. Construct 

 the triangle and find the current and power factor. (2 min.) 



3. Two circuits have resistances of 5 and 20 ohms, and their 

 capacities are respectively 100 microfarads and infinity. If they 

 are in series on a 200-volt circuit with co = 400, find the current 

 and power factor. (2 min.) 



4. A circuit with 15 ohms resistance and 0.02 henry inductance 

 connects a 500-volt alternator to a 120-microfarad condenser; 

 co is 500; find the current and the angle of lag or lead. (4 

 min.) 



5. A condenser of 12.5 microfarads is fed through a resistance 

 of 100; the maximum current is 1 and co is 400. Plot sine curves 

 of current and condenser e.m.f., and hence determine the curve of 

 impressed e.m.f. Construct the vector parallelogram for these 

 three curves. (10 min.) 



6. In problem 5 replace the resistance with an equal impedance 

 in which the power factor is 0.707. Plot the curves of active, 

 induced and condenser e.m.f. and from them determine the im- 

 pressed e.m.f. curve. (15 min.) 



7. In problem 5 what reactance would have to be inserted to 

 bring the current into phase with the impressed e.m.f.? Also for 

 the circuits of problems 4 and 6 of Chapter V? (2 min.) 



8. Given for a circuit: E = 100 sin0; R = 2; L = 0.01; co = 

 600; capacity = 0.001. Find the equation for the instantaneous 

 currents. (4 min.) 



9. An over-excited synchronous motor takes 130 amperes with 

 a power factor of 50%. What will be the e.m.f. at its terminals 



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