Atmospheric Pressure and Gauge Pressure
Pressure is measured in newtons per square meters, N / m2; this is known as a pascal, Pa.
1 pascal = 1 Pa = 1 [ N /
m2 ]
Other units:
1 atm = 1.013 x 105
Pa
1 bar = 100 kPa = 1 x 10
5 Pa
( 1 atm = 1.013
bar)
1 mm Hg = 133
Pa
1 atm = 760 mm
Hg
This is also known as a Torr, named for Torrecelli,
1 Torr = 1 mm
Hg
1 atm = 760
Torr
What is the pressure PC in this chamber?
We may measure it in mm Hg. That is really the difference between atmospheric pressure Po and the pressure PC in the chamber.
This term on the right is called gauge pressure. Absolute pressure is gauge pressure plus atmospheric pressure,
