CHAPTER IX. 



ELECTRICAL MEASUREMENT. 



Having given a short account of some of the 

 sources of electricity, let us now proceed to 

 describe some of the practical uses to which 

 it is put, and at the same time describe the 

 operation of the appliances used. Before pro- 

 ceeding further, however, we ought to tell how 

 electricity is measured. We have pounds for 

 weight, feet and inches for lineal measure, and 

 pints, quarts, gallons, pecks and bushels for 

 liquid and dry measure, and we also have 

 ohms, volts, amperes and ampere-hours for 

 electricity. 



When a current of electricity flows through 

 a conductor the conductor resists its flow more 

 or less according to the quality and size of the 

 conductor. Silver and copper are good con- 

 ductors. Silver is better than copper. Call- 

 ing silver 100, copper will be only 73. If we 

 have a mile of silver wire and a mile of iron 

 win- and \v:uit the in>n wire to carry as much 

 electricity as the silver and have the same bat- 

 tery for both, we will have to make the inm 

 over seven times as large. That is, the 

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