ANIMAL AND VEGETABLE 



95 



Let C and D (Fig. 8) represent two condensers with 

 capacities of 15 and 5 microfarads respectively, and B 

 cells of an electromotive force of 3 volts ; the distance 

 between the plates of C being equal to a and between those 

 of D equal to b. 



a 



Fig. 9. 



In the above figure the same pair of condensers show 

 under the conditions which actually regulate the test of 

 their joint capacity ; the inner plates of both having been 

 eliminated. 



C and D are now, to all intents and purposes, a single 

 condenser with, it is important to observe, a distance 

 between its plates equal to a + b. Without calculation it 

 will be recognised that the joint capacity of the pair must 

 be smaller than the capacity of either of them if tested 

 alone, because of the increased distance between the 

 plates. 



Upon closing the battery circuit the outer plates of C 

 and D are equally and oppositely charged to the potential 

 difference of the battery, viz., 3 volts. When this potential 

 difference has become established, the current from the 

 battery will cease to flow. The neutral condition of the 

 inner plates of C and D has, meanwhile, been disturbed by 



