SUMMARY 



229 



kilowatt-hours. The kilowatt is 1,000 watts (c/. 9: 

 kilogram, kilometer, etc.). A kilowatt is equal to 1.34 

 horse powers (c/. 26). A kilowatt-hour is an electric 

 power of one kilowatt working for one hour. It is the 

 common unit used by electric companies in selling power 

 to consumers. The watt is named for James Watt, the 

 inventor of the steam engine (c/. 24). 



The common electric watt-hour meter is really a tiny, finely-built 

 electric motor (c/. 161). The "field" of the electromagnets of the 

 motor is produced by the current to be measured, and exerts force 

 on the "armature," causing it to revolve. The armature is delicately 



10,000 



1,000 



100 



KILOWATT HOURS 



Fig. 215. 

 Electric Kilowatt-Hour Meter. 



mounted, on steel balls and jewels. As the armature revolves, it gives 

 motion to clock gear-wheels, and these in turn move the hands of 

 the dials (Fig. 215). Note the direction in which the hand of each dial 

 has moved to bring it to its present position, and write down the read- 

 ing of the meter. 



260. Summary. Modern conveniences are due to scientific dis- 

 coveries and their application. 



We need an abundance of water for our houses, our industries, and 

 our community life. 



Plumbing is the system of pipes, etc., that brings water to the 

 house, and carries water and waste away from it. 



Traps keep sewer air out of the house. 



