82-85] 



Series of Condensers 



It is further found that on replacing air by some other dielectric, the 

 capacity of a condenser is altered in a ratio which is independent of the 

 shape and size of the condenser, and which depends only on the dielectric 

 itself. This constant ratio is called the specific inductive capacity of the 

 dielectric, the inductive capacity of air being taken to be unity. 



We shall discuss the theory of dielectrics in a later Chapter. At present 

 it will be enough to know that if C is the capacity of a condenser when its 

 plates are separated by air, then its capacity, when the plates are separated 

 by any dielectric, will be KC, where K is the inductive capacity of the 

 particular dielectric used. The capacities calculated in this Chapter have all 

 been calculated on the supposition that there is air between the plates, so 

 that when the dielectric is different from air each capacity must be multi- 

 plied by K. 



The following table will give some idea of the values of K actually 

 observed for different dielectrics : 



Sulphur 3'84 



Resin 2'55 



Paraffin 2'32 



Ebonite 3'15 



Glass about 7. 



COMPOUND CONDENSERS. 



Condensers in Parallel. 



85. Let us suppose that we take any number of condensers of capacities 

 C lt C z , ... and connect all their high potential plates together by a conducting 



FIG. 31. 



This is 



wire, and all their low potential plates together in the same way. 

 known as connecting the condensers in parallel. 



The high potential plates have now all the same potential, say V lt while 

 the low potential plates have all the same potential, say F . If lt e. 2 , ... are 

 the charges on the separate high potential plates, we have 



