34 



ELECTRICAL ENGINEERING 



From the last two examples it is seen that a uniform field can 

 be made non-uniform by introducing dielectrics of various specific 

 inductive capacities, and that the stress in the various dielectrics 

 varies inversely as their specific inductive capacities. 



(4) In Fig. 27 a cylinder of dielectric constant K is introduced 

 into the uniform field as shown. 



\ 



\ 



FIG. 27. 

 The stress in the air is 



FIG. 28. 



and is the same as before the cylinder was introduced. 

 The stress in the dielectric is also 



E 



but the induction density in the dielectric is 



The permeance of the path is increased and an increased flux 

 is produced passing between the plates, but since the increased 

 flux is all confined to the cylinder there is no increase in the stress 

 in the air. 



