238 Prof. E. Taylor Jones on most Effective Primary 



the optimum primary capacity should be more than twice as 

 great as the value necessary for " resonance/' The maximum 

 value of V 2 i n this case i s numerically, by (14), 



V 2 „, = 2-267^°* (16) 



The adjustment recommended by Drude (P = 0*36, 

 L 1 Ci = L 2 C 2 ) gives for the maximum secondary potential 



V 1TO = l-667-^-° (17) 



Even at this degree of coupling, however, a higher 

 secondary potential may be obtained with a larger primary 

 capacity. For example, the adjustment P = - 36, 

 L l C 1 = 2L 2 C 2 , gives the frequency-ratio n 2 /n 1 = 2*197, and a 

 maximum secondary potential, at time t = 0'925/2n 1} the 

 value of which is 



V 2 „,= 1-998 L ^- (18) 



From these examples it will be seen that Drude's rule 

 does not in general give even approximately the correct 

 value of the optimum primary capacity. The most effective 

 capacity is generally greater than the ki resonance" value. 



In some preliminary experiments made by the writer last 

 summer, it was found that in certain cases the best effect was 

 obtained with a primary capacity considerably greater than 

 that required to make the periods of the two circuits equal 

 when separated, but a more extended series of experiments 

 is in progress in the laboratory with the object of determining 

 the best value of m for various values of k' 2 . 



The conditions are very different if the primary capacity 

 is kept constant and L x is varied, e. g. by means of variable 

 series inductance in the primary circuit. In this case L 21 

 is constant, k 2 is inversely proportional to L 1? and the co- 

 efficient of (cos2ttw 1 £ — cos27rw 2 £) in (H) has a maximum 



value of -^ \ / -f^ . — l when m = l. If in addition ?z 2 = 2n 1 



(k 2 = 0*36) the numerical maximum of V 2 is given by 



v 2m =v, 



i-21 Ul 



2m— V Q /\ / -. ,p- 

 V Jj 12 l^ 2 



* The adjustment k'- — G'2Qc, »i=l, gives approximately 



V 2 ,n-r88 L 2L V /L r 



