ELECTRICAL INVENTIONS 



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of the resistance expressed in ohms, multiplied by the square of 

 the current intensity expressed in amperes, multiplied by the 

 time expressed in seconds. 



Each of the many kinds of available batteries possesses 

 certain advantages but also certain disadvantages. There is, 



FIG. 96. Diagram of a kilowatt-hour meter 



therefore, no single battery which is superior for general use. 

 A battery must be selected for the particular work it is intended 

 to accomplish. The several kinds of batteries differ from each 

 other chiefly in their length of life and in the voltage of the 

 current produced, its electromotive force, its constancy, its 



