2O 



ELEMENTS OF ELECTRICAL ENGINEERING. 



electric current and then in stopping it and starting it again in the 

 opposite direction. 



The alternating pressure generated by the pump in Fig. 19 

 must not only overcome the resistance of the pipe and the inertia 



pipe 



J 



pipe 



Fig. 17. 



Fig. 18. 



of the water in the pipe, but a portion of the pressure developed 

 by the pump must be used to distort the elastic diaphragm DD 

 which bridges across the chamber CC. Similarly, the alternating 



Pipe 



I 



c 



Pipe 



C 



D 



C 



Fig. 19. 



Fig. 20. 



electromotive force generated by the alternator in Fig. 20 must 

 not only overcome the electrical resistance of the wire and the 

 electrical inertia, or inductance, of the circuit, but a portion of the 



