24 



ELECTRICAL ENGINEERING 



wire B placed at a distance H cm. below the earth. Its potential 

 would be E. 



The difference of potential between A and B is 2 E and from 

 equation 26 



2 rl R 



thus the capacity of the single wire in relation to the earth per 

 centimeter length is 



a 1 



- q - 



2H-R 01 2H-R 

 2 q log 5 2 log 



e.s. units, . (46) 



R R 



and the capacity in farads per mile is 



38.8 X 10- 9 



logio 



2H -R' 

 R 



(47) 



FIG. 19. Capacity of sphere to earth. 



(e) Capacity of a sphere of radius R cm. at height H cm. above 

 the earth. In Fig. 19 A is a sphere of radius R cm. at a height 

 H cm. above the earth. If A is raised to a potential E above 

 earth potential, a dielectric flux \f/ is produced passing from the 



