28 



ELECTRICAL ENGINEERING 



Equation 52 may be expressed in two other forms by substi- 

 tuting for E its value -^; 



or 



2 C- 



(53) 

 (54) 



FIG. 22. Energy stored in a condenser. 



If the area of the plate P is A square centimeters, then the 

 dielectric flux density between the plates is 



2) = - lines per square centimeter, 



and the electrostatic force is 



cF = VF dynes. 

 A 



