CHAPTER VIII. 



THE PHENOMENA OF ELECTROSTATICS. 



106. The voltaic cell (or dynamo) versus multiplying devices for 

 the production of large electromotive forces. A locomotive engi- 

 neer, knowing that an ordinary locomotive can exert about 1 5,000 

 pounds of draw-bar pull, and, wishing to observe the behavior of 

 a bar of steel when subjected to a stretching force of 1 50,000 

 pounds, might arrange to use ten locomotives hitched together to 

 exert the desired force ; but if the bar of steel should break, then 

 the dormant energy of the locomotives would come into action, 

 about 1 0,000 actual horse-power would have to be taken care of, 

 and a terrible wreck would probably be the result. The value of 

 a locomotive lies in the fact that it can contimie to pull even when 

 the thing it pulls on yields , as it were, at a speed of 60 miles per 

 hour ; but for exerting a large force upon a thing which does not 

 yield rapidly, some sort of a force-multiplying device, such as a 

 screw or a lever, is more convenient and incomparably cheaper 

 and safer than a battery of locomotives. 



An electrician, knowing that an ordinary dry cell has an elec- 

 tromotive force of about 1.5 volts, and, wishing to observe the 

 effects when the air between two metal plates is subjected to a 

 high electromotive force, might think of connecting 100,000 dry 

 cells in series to exert 1 50,000 volts ; but if the air should break 

 down, then the dormant energy of the battery would come into 

 action, about 1,000 actual horse-power would have to be taken 

 care of, the apparatus would in all likelihood be destroyed, and 

 if the body of the electrician should by accident become a portion 

 of the battery circuit, he would be instantly killed. The value of 

 the battery or dynamo lies in the fact that it can continue to push 

 even when the circuit upon which it pushes yields at a "speed" of 

 many amperes ; but for exerting a large electromotive force across 



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