298 



Dr. Norman Campbell : Experiments on 



As is to be expected, the damping is considerably less at the 

 same frequency than before, but the same general features 

 are shown, /jl increases with the frequency and, for the same 

 frequency, fi' is much less than fi. 



Fisr. G. 



4000 



2000 



1000 













•s'* 











> 











ee G( 



' OG oo 



o 



** *^ «« 



'"■ ^ 1— 











.{ 



C.fmf) °' 



0-2 



0-5 



The peak potentials were then corrected in the same 

 manner as before for the observed damping, and the dotted 

 curve in fig. 5 obtained. The ratio of observed to calculated 

 peak potential is 0*76 at Cx = and 0*88 at Oj = 4 — almost 

 exactly the same ratios as were found in the previous 

 experiments ; it will appear later that the same ratios 

 reappear in experiments on an armature of quite different 

 construction. It would seem, therefore, that the coincidence 

 of the value of this ratio is not wholly accidental ; but it 

 cannot be determined at present what theoretical significance 

 is to be attributed to the agreement. 



General Conclusions. 



10. The main conclusion to be derived from these expe- 

 riments is that a theory which introduces only constants 

 characteristic of the windings of the armature will not lead 

 to values for the peak potential which are, even approximately, 

 in accordance with experiment. By far the most important 

 factor in determining what peak potential will be obtained is 



