difference between gauge pressure and absolute pressure

 ATMOSPHERIC PRESSURE:-

The atmospheric air exerts a normal pressure upon all surfaces with which it is in contact and it's called ATMOSPHERIC PRESSURE. It is also known as BAROMETRIC PRESSURE. The ATMOSPHERIC PRESSURE at sea level (above absolute zero) is called standard ATMOSPHERIC PRESSURE and its value is...


STD.ATMOSPHERIC PRESSURE = 101.3kN/M2 or kPa 

                                                          = 10.3 m of water

                                                          = 760 mm of Hg

GAUGE PRESSURE:-

The pressure measured with the help of pressure is known as Gauge pressure, in which ATMOSPHERIC PRESSURE is taken as the datum. All the pressure gauges record the difference between the actual pressure and the ATMOSPHERIC PRESSURE. The actual pressure is known as ABSOLUTE PRESSURE.



Now,                                 Absolute pressure = Atmospheric pressure + Gauge pressure(+ve)

This relation is used for pressure above atmospheric, for +ve gauge pressure, 

for pressure below atmospheric, the gauge pressure will be (-ve)

Therefore,,     Absolute pressure = Atmospheric pressure - negative gauge pressure or vacuum pressure                                                                                                     

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