ELECTRIC CHARGE. THE CONDENSER. 



167 



diaphragm DD and the two compartments are connected to a 

 pump P. The electromotive force of the battery in Fig. 103 

 forces a certain amount of charge q into the plate AA, draws 

 the same amount of charge out of the plate BB, and subjects 

 the dielectric DD to an electrical stress. The pressure-differ- 

 ence developed by the pump P in Fig. 104 forces a certain 



D 



R 



wre 

 B 



water I water 



Fig. 103. 



Fig. 104. 



amount of water q into the compartment AA, draws the same 

 amount of water out of the compartment BB, and subjects the 

 rubber diaphragm DD to a mechanical stress. If the pump P 

 in Fig. 104 is removed and the two compartments connected by 

 a pipe, the mechanical stress of the diaphragm DD will be 

 relieved by a momentary flow of water from A to B through 

 the pipe. If the battery in Fig. 103 is removed and the two 



plates connected by a wire, the electrical stress of the dielectric 



f J 



DD will be relieved by a momentary flow of electric current 

 through the wire. When the pump P in Fig. 1104 is connected, 

 as shown, it causes water to flow out of B into A until the 

 pressure-difference developed by the pump is balanced by the 

 elastic reaction of the diaphragm DD, and the amount of water 

 drawn out of B and forced into A is proportional to the 

 pressure-difference developed by the pump. When the battery 

 B is connected to the plates in Fig. 103, it causes an electric 

 current to flow out of B and into A until the electromotive 



