r 



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\ 



















1 



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160 Prof. E. Taylor Jones on the Potential 



In fig. 6 is shown a part of the calculated (u, U sin 0) curve 

 for the coupling P=0*7, s being taken as 1*05. The highest 

 point of the first arch occurs at u= 0'465, the minimum at 

 ^ = 0*19, and the second maximum at xi — 0*095. So far as 



Fig. 6. 



HO 



-^t-os 



^ 1-0 



0-35 



01 02 0-3 04 0-5 0-6 0-7 0-8 OS 1-0 

 u 



Calculated {u, U sin <j>) Curve for a Magneto. 

 #=0-7. 5=1-05. 



the proportions of the first arch (on the right) are con- 

 cerned, the curves of figs. 5 and 6 are very similar : there 

 is much the same percentage drop in both from, say, the 

 maximum to a point of double or one-half its abscissa, and 

 the ratio of the abscissae at which the maximum and the 

 minimum occur is not very different in the two curves. 

 The chief point of difference between the curves is in the 

 ratio of the two maxima. In this respect the calculated 

 curve for P = 0*66 would agree much better with the experi- 

 mental curve, but it would show considerably greater 

 deviations from it in other features, especially in the 

 ratio of the capacities at which the two maxima, and at 

 which the first maximum and the minimum, occur. 



On the whole, the curve for the coupling k 2 = 0'7 (fig. 6) 

 appears to be in closest agreement with the experimental 

 curve ; and the relative smallness of the second maximum 

 in the latter may arise from several causes which would 

 operate more strongly at the higher frequencies — e. g., the 

 " lag " of the spark, the influence of frequency on the 

 inductances, and the difficulty of securing good interruptions 

 when the capacity in parallel with the break is very small. 



Additional evidence in support of the view that the 

 coupling — with the small series inductance in the primary 

 circuit — is not far from 0*7 is found in the manner in which 

 the optimum capacity varies when the series inductance is 

 altered. If this inductance (L 3 ) is increased the optimum 



