Atmosphere (unit)
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When expressed as a measurement, an atmosphere (symbol: atm) or standard atmosphere is a unit of pressure roughly equal to the average atmospheric pressure at sea level on Earth. It is defined as 101.325 kPa and equal to the pressure under 760 mm of mercury.
- 1 atm
- = 1013.25 hPa = 1013.25 mbar
- = 101.325 kPa
- = 760 mm of mercury (mmHg)
- = 29.92 inches of mercury
Applications
In chemistry, standard temperature and pressure (STP) is defined as a reference temperature of 0 °C (273.15 K) and pressure of 101.325 kPa (1 atm).In the United Kingdom, scuba divers and others often use the word atmosphere loosely to mean 1 bar (1000 millibars, or 100000 Pa).
The unit technical atmosphere (at) is roughly equal to the gauge pressure under 10 m of water; 1 at = 98066.5 Pa.
| Pascal (Pa) | Bar (bar) | Technical atmosphere (at) | Atmosphere (atm) | Torr (mmHg) | Pound per square inch (psi) | |
|---|---|---|---|---|---|---|
| 1 Pa | N/m² | 10−5 | ||||
| 1 bar | 100 000 | 6 dyne>dyn/cm² | 1.0197 | 0.98692 | 750.06 | 14.504 |
| 1 at | 98 066.5 | 0.980665 | kgf/cm² | 0.96784 | 735.56 | 14.223 |
| 1 atm | 101 325 | 1.01325 | 1.0332 | Pa | 760 | 14.696 |
| 1 Torr | 133.322 | mmHg | ||||
| 1 psi | 6,894.76 | 51.715 | lbf/in² |
Example reading: 1 Pa = 1 N/m² = 10−5 bar = 10.197×10−6 at = 9.8692×10−6 atm ....etc.
Note: mmHg is an abbreviation for millimetres of mercury.
External links
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