76 



THE ROYAL SOCIETY OF CANADA 



VOLTS 



If C2 is very large compared with Ci, this becomes C = Ci and the 

 apparent capacity is that of the smaller condenser. If Ci is not suffici- 

 ently small, then C depends on C2. 



If we add a small charge, dq, to the electrometer, the capacity 

 changes by the amount 



C1MC2 + C2MCX 



(Ci + C2)2 



So the change in observed capacity depends on CiMC2+C2MCi. 



In many of the observed cases dCi is negative, while dC2 is always 

 positive. If we assume that this is always true, then C may increase, 

 decrease or remain stationarv if C1MC2-C2MC1 is greater than, less 



than, or equal to respectively. 



if 



equal to 





dC2 

 dCi 



is greater than, less than, or 



Examination of Figure 1 (which is for the case where C2 is 

 very large compared with Ci and hence C = Ci) we see that the 

 changes in capacity for negative charging are very large compared 



