ELECTRIC FIELD. 143 



Cln farads = * k ' ~ (4) 



where B, a and x are the same as in equation (i), and k is the 

 inductivity of the dielectric. 



As before, let E be the electromotive force between the plates ; 

 then: 



|i*f ; > >> (5) 



Tjt 



But : : is the electrical field intensity or the electrical stress in 



E 



the dielectric, and if we define k as the electrical flux density 



x 



E 

 in the dielectric, then k a will be the total electric flux from 



plate to plate. Consequently the electric flux going out from -j- q 

 coulombs or the electric flux coming in to q coulombs is Bq 

 volt-centimeters, where B is a constant whose value is given in 

 equation (2). This is Gauss's theorem, and although it has 

 been established for a very special case, it is entirely general ; Bq 

 volt-centimeters of electric flux always goes out from + q or 

 comes in to q coulombs of charge. 



87. Electric field intensity and electric flux density. Mechan- 

 ical, magnetic and electric analogies. Let e be the intensity of 

 an electric field at a point in a dielectric of which the inductivity 

 is k', then 



F = ke (i) 



where F is the electric flux density at the point. 



Magnetic and Electric Parallel. 



F = ke 



Where & is intensity of 

 magnetic field in gausses, /* is 

 the permeability of the me- 

 dium, and cB is the magnetic 

 flux density. See Arts. 54 and 

 57- 



Where e is intensity of elec- 

 tric field in volts per centimeter 

 (E/x), k is the inductivity of 

 the medium, and F is the 

 electric flux density in volt-cen- 

 timeters per square centimeter. 



