Fig 6.21 shows a manometer used to measure the pressure difference between the air inside a plastic container and the atmosphere outside a pressure difference of 100 Pa causes a one centimeter difference in water lvl a) Using Fig 6.21 determine the pressure difference in Pa shown by manometer
Answers
Explanation:
(a) For figure (a)
Atmospheric pressure, P
0
= 76 cm of Hg
Difference between the levels of mercury in the two limbs gives gauge pressure
Hence, gauge pressure is 20 cm of Hg.
Absolute pressure = Atmospheric pressure + Gauge pressure
=76+20=96cm of Hg
For figure (b)
Difference between the levels of mercury in the two limbs =–18cm
Hence, gauge pressure is –18 cm of Hg.
Absolute pressure = Atmospheric pressure + Gauge pressure
=76cm–18cm=58cm
(b) 13.6 cm of water is poured into the right limb of figure (b).
Relative density of mercury = 13.6
Hence, a column of 13.6 cm of water is equivalent to 1 cm of mercury.
Let h be the difference between the levels of mercury in the two limbs.
The pressure in the right limb is given as:
PR= Atmospheric pressure + 1 cm of Hg
=76+1=77cm of Hg ….. (i)
The mercury column will rise in the left limb.
Hence, pressure in the left limb, PL=58+h ..... (ii)
Equating equations (i) and (ii), we get:
77=58+h
∴h=19cm
Hence, the difference between the levels of mercury in the two limbs will be 19 cm.
Answer:60000 Pa
Explanation: the difference between the water level is 60 cm and if 100 Pa = 1 centimeter then 60 centimeter is equal to 60,000 pa