Vacuum

For other uses, see vacuum cleaner and Vacuum (musical group).

Partial vacuum

Physicists use the term partial vacuum to describe real-life non-ideal vacuum. A complete characterization of the physical state would require further parameters, such as temperature. The antithesis of a vacuum, which is also an ideal unachievable state, is called a plenum.

Related Topics:
Temperature - Antithesis - Plenum

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In engineering, a vacuum is any region where the gas pressure is less than atmospheric pressure. Engineers measure the degree of vacuum in units of pressure. The SI unit of pressure is the pascal (abbreviation Pa), but vacuum is usually measured using the torr, which equals 133.3223684 pascals. It is often also measured using the barometer scale, or as a percentage of atmospheric pressure using the bar. For commercial purposes, vacuum is often measured in inches of mercury (inHg). This means that the pressure in vacuum, when specified in inches of mercury, is equal to the specified inches of mercury subtracted from 29.92. Thus a vacuum of 26 inHg is equivalent to a pressure of (29.92 - 26) or 3.92 inHg. Here, 29.92 inHg means perfect vacuum.

Related Topics:
Engineering - Pressure - SI - Pascal - Torr - Barometer - Atmospheric pressure - Bar - Mercury

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