Q 10.22 A manometer reads the pressure of a gas in an enclosure as shown in Figure (a) When a pump removes some of the gas, the manometer reads as in Figure (b) The liquid used in the manometers is mercury and the atmospheric pressure is 76 cm of mercury.
(a) Give the absolute and gauge pressure of the gas in the enclosure for cases (a) and (b), in units of cm of mercury.
In figure (a)
Gauge Pressure = 20 cm of Mercury
Absolute Pressure = Atmospheric Pressure + Gauge Pressure
Absolute Pressure = 76 + 20= 96 cm of Mercury
In figure (b)
Gauge Pressure = -18 cm of Mercury
Absolute Pressure = Atmospheric Pressure + Gauge Pressure
Absolute Pressure = 76 + (-18)= 58 cm of Mercury