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Define gauge pressure. When is gauge pressure (i) positive (ii) negative ? Give two examples where gauge pressure is more relevant. |
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Answer» Definition : Gauge pressure is the pressure exerted by a fluid relative to the local atmospheric pressure. Gauge pressure, pg = p - p0 where p is the absolute pressure and p0 is the local atmospheric pressure. When the pressure inside a closed container or tank is greater than atmospheric pressure, the pressure reading on a pressure gauge is positive. The pressure inside a ‘vacuum chamber’-a rigid chamber from which some of the air is pumped out-is less than the atmospheric pressure, so a pressure gauge on the chamber designed to measure negative pressure reads a negative value. At a depth within a liquid of density ρ, the gauge pressure is pg = p – p0 = hpg Examples : Tyre pressure gauge, blood pressure gauge, pressure gauge on an oxygen or scuba tank. |
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