45 



EXPERIMENT 35. TO FIND HOW MUCH GAS YOUR HOME 

 USES IN A WEEK OR MONTH 



Read your home gas meter once a week, the same day 

 each time, for five weeks, recording in your notebook the 

 position of the dial hands at each reading. From these 

 five readings find the number of cubic feet of gas used in 

 your home in each of the four weeks ; calculate the amount 

 used in the entire time. What has been the total cost ? the 

 cost per week ? 



If the amount jof gas consumed has varied much from 

 week to week, can you suggest any explanation ? 



EXPERIMENT 36. BOYLE'S LAW 



(a) Support in an upright position a bent glass tube, of 

 which the short arm is closed and the long arm open, as 

 shown in Figure 33. Pour mercury into the tube until it 

 stands at the same level, ab t in the 

 two arms. The air in the long arm is 

 pressing upon the mercury in that 

 arm and is tending to force it up the 

 short arm. The air in the short closed 

 arm is pressing down upon the mercury 

 in that arm and tending to send it up 

 the long arm. Since the mercury is 

 at the same level in the two arms, 

 the pressure in the long arm must be 

 equal to the pressure in the short arm. 

 But the long arm is open, and the 

 pressure in that arm is the pressure 

 of the atmosphere. Therefore the FIG. 33 . Boyle's Law. 



