Galvanometer Deflection. 



413 



Q. 



Values of C for different values of n. 



50. 



100. 



200. 



2780 



3780 



8780 



12780 



•2448 

 •2359 

 •1798 

 •1424 



•2211 

 •2126 



•1829 

 •1568 



•2128 

 •2062 

 1822 

 •1657 



When the value of n is less, the value of C ought to fall 

 quicker as Q increases. This is confirmed by the following 

 result of a series of experiments in which n had the value 10 

 very nearly : — 



Q. 



0. 



D. 



2780 



5480 



10480 



12780 



0774 

 •0475 

 0242 

 •0194 



1237 

 1637 

 1774 



1796 



The column D gives the first four figures of the reciprocal of 



CQl 1 + KP + LQ.T 



which ought to be constant if I 2 followed formula (A). It 

 will be seen that D is not very far from being constant, the 

 differences getting less as Q increases. This is what we should 

 expect. 



If instead of using the induction-coil in the usual way we 

 throw the battery into the coil usually used as the secondary, 

 and put the galvanometer into the small-resistance coil com- 

 monly used as the primary, then the induced currents, even 

 with the 200 fork, will not interfere. We must in this case 

 put in formula (A), which is now perfectly applicable, 



L = 52, M = -79, N=-013, P = 2720 (say), Q = 68, 

 the last arising practically from the galvanometer resistance. 

 Hence 



NT 



_ =-010 



LQ + NP 



and when Q is doubled its value is *005 ; so that the fraction 

 contributed by the current at make to the value of I 2 is now 

 comparatively small. Hence C will approximately vary in- 

 versely as the resistance Q, and C ought to drop to nearly 

 half its value when Q is doubled. 



The experiment was tried with twenty-five small Leclanche 

 cells in the secondary of the induction-coil ; the breaking-fork 



