MEASURING ELECTRICITY 369 



five watts, and they are all lighted for an hour, we would 

 then be using 10X25 or 250 watts an hour, and in five 

 hours this would be 5X250 or 1250 watt hours. The watt 

 is the unit by which we measure electrical energy. One 

 thousand watts make one kilowatt and one kilowatt used for 

 one hour equals one kilowatt hour. Electricity for the ten 

 lamps, using 1250 watt hours or 1.25 kilowatt hours, would 

 cost, at twelve cents per kilowatt hour, fifteen cents per 

 hour. A study of the diagram shows that of the four dials, 

 the one to the left moves the least, while the one to the right 

 moves the fastest. The four dials indicate thousands, 

 hundreds, tens, and units. Study the diagram. If the 

 thousands hand is between i and 2, it will indicate 1000 ; 

 if the hundreds hand is 

 between 6 and 7, it in- 

 dicates 600; if the tens 

 hand is between 5 and 

 6, that will be 50, and 

 the units hand, between 



, . , Wattmeter dials. 



9 and o, is read 9, 



making a total of 1659 kilowatt hours. If the previous 

 reading had been 1610, that would mean that we have used 

 49 kilowatt hours since the meter was last read. We have 

 already shown under the chapter on lighting some ways 

 to reduce the 'electric light bill through the use of the 

 tungsten lamps, but if our meter bill seems high, we 

 should inquire into the cause. The large bill may come 

 from some leakage, from a forgotten light in a closet or 

 attic left burning, from defective wiring which may 

 allow a current to flow when no lights are in use, and 

 rarely from an error in the meter itself, or in the reading 

 of the meter by the man sent from the electric company. 



H.-WHIT. CIV. SCI. IN THE HOME 24 



