230 Prof. E. Taylor Jones on most Effective Primary 



(smaller) maximum near w = 0'46 (Ci = 0'28 mfd.). The 

 maxima corresponding to the higher ratios 11, 15, . . . are 

 more difficult to demonstrate experimentally owing to the 

 smallness of the primary capacities required and the con- 

 sequent difficulty of obtaining good interruptions. 



Fig. 2 shows the curves for the case F = 0*571, the first 



Fte. 2. 



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Curve showing the variation of maximum secondary potential of an 

 induction-coil when the primary capacity is varied, k 2 being 0-571. 



of the unit-efficiency values. In this case the greatest 

 maximum of U sin (nJ^ — Z, <£ = 7r/2) agrees with the 

 maximum of U, both occurring at w = 0*429. There is a 

 minimum of Usinc/> at w = 0'l, and a series of diminishing 

 maxima at smaller values of u, the first of which occurs at 

 w = 0*06, near the 7/1 coincidence. In this case also some 

 of the main features of the U sin <j> curve can be followed by 

 observing spark-lengths. The coupling coefficient of the 

 18-inch coil being reduced, by the addition of series in- 

 ductance to the primary circuit, so that A: 2 = 0*5 71, the greatest 

 spark-length is found to be given by the primary capacity 



