PROBLEMS. 



381 



makes 25 revolutions per second. Plot the electromotive force 

 curve, neglecting fringes of field at corners of pole pieces, and 

 determine average value and effective value of the electromotive 

 force during each half cycle. The long and short air gaps under 

 the 1 80 pole face are as 2:1. Ans. Average value is 0.5 volt 

 during each half-cycle ; effective value is 0.707 volt in the half- 



Fig. 8/>. 



cycle corresponding to the 90 pole face, and 0.5303 volt in the 

 half-cycle corresponding to the 1 80 pole face. 



9. Plot the curve of current which would be produced by the 

 electromotive force of the alternator of problem 8, in a circuit 

 containing inductance only, the inductance of the circuit being 

 O.I henry. 



Note. The current curve here required is strictly indeterminate, as explained in 

 the note to problem 5. Determine the current curve on the basis of the assumption 

 specified in the note to problem 5. 



10. Plot the curve of current which would be produced by the 

 electromotive force of the alternator of problem 8 in a circuit con- 

 taining a condenser but having a negligible resistance. If it is 

 impossible to plot the curve state what assumptions in problem 8 

 and in this problem make the plotting impossible. 



11. The following are instantaneous values, in volts, of the 

 electromotive force of an alternator, taken at equal intervals during 

 an entire circle : o, 30, 60, 80, 90, 95, 90, 80, 60, 30, o, 30, 

 60, 80, 90, 95, 90, 80, 60, 30 and o. The 



