CPB 314 Lecture 4: CPB 314 (4)
9 Mar 2017
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Document Summary
Pressure: a normal force exerted by a fluid per unit area. Absolute pressure: the actual pressure at a given position. It is measured relative to absolute vacuum (i. e. , absolute zero pressure). Gage pressure: the difference between the absolute pressure and the local atmospheric pressure. Most pressure-measuring devices are calibrated to read zero in the atmosphere, and so they indicate gage pressure. Atmospheric pressure is measured by a device called a barometer; thus, the atmospheric pressure is often referred to as the barometric pressure. A frequently used pressure unit is the standard atmosphere, which is defined as the pressure produced by a column of mercury 760 mm in height at 0 c(hg = 13,595 kg/m3) under standard gravitational acceleration (g = 9. 807m/s2). It is commonly used to measure small and moderate pressure differences. A manometer can contain one or more fluids such as mercury, water, alcohol, or oil.
