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BELL SYSTEM TECHNICAL JOURNAL 



cut-off {Ec = — 350) the amount of error is indicated by the two 

 points illustrated in Fig. 11. ^ is the case for a peak exciting voltage 

 of 300 volts. From the static characteristics of Fig. 9 we find that 

 Cpm will be about 2300 volts which will make — 230 volts, the peak of 

 the real cut-off curve (— ep/ij.) and since it is a sine wave we can plot 



»- -100 



_l 



o 



<a 



cr> -200 



20 



40 



60 



80 100 



DEGREES 



Fig. 11 — Illustrating method of obtaining actual period of flow of plate current. 

 a, acutal cut-off point, h, cut-off point assumed in calculations. 



it as shown. The error in the period of flow then will be represented 

 by the difference between where the c,, curve cuts the — 300-volt line 

 and where it cuts the — e^l ix curve. The actual period of flow is 

 about 156° instead of 160° as found before, which would make K 

 = 0.425 instead of 0.435. B is the case for a peak exciting voltage of 



