5.A manometer can be used to find the pressure of a gas. The difference in the level of the liquid in each side of the tube indicates the difference in pressure on the water surface at A and the pressure of the gas on the water surface at B(Assume atmospheric pressure is 100k pa). Calculate the pressure of gas at C Water density =1000kg/m3 u
Answers
P 0 (atmospheric pressure)
= 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
Explanation: