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 ]
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,
(c) 2005, Doug Davis; all rights reserved