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Normal ( Standard ) Atmospheric Pressure : It's the maximum atmospheric
pressure at sea level .
to obtain it at 0 C , the length of mercury column is 76 .
Pa = hg = 13595 * 0.76 * 9.8 = 1.013 * 10^5 Pascal's ( N/m^2)
international units
= 1.013 Bar = 76 cm.hg = 760 mm.hg ( Torr )
Equivalent units
so
| 1 Bar = 10^5 Pascal |
| 1 Torr = 1 mm.Hg |
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1 millibar = 100 Pascal's
Q. Mercury is
suitable barometric material?
It forms short columns in the
barometer due to its high density ( 76 cm for normal )
it's non wetting to glass, of low vapor pressure & can be
easily detected .
The water is not suitable as it forms a columns of height
10.33 m due to its low density . also it has high vapor
pressure and wetting to the glass .
Using the Barometer as
Altimeter :
It measures the altitude, e.g. aero plane, or
heights of buildings or mountains.
Atmospheric Pressure is measured by the barometer once
at the base and another time at the top of the building
.
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Delta Pmercury = Delta Pair or rDelta
H1g = rDelta H2g
r1Delta H1 ( Hg ) = r2Delta
H2 ( air )
Where Delta h1 is the difference of the reading of the
barometer, and Delta h2 is the height of the
corresponding air column which is equal to the height of
the building .
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