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# Physical Constants

## Physical constants - SI Units.

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Physical Constants
DescriptionSymbolFormulaValue1Unit1Value2Unit2
Absolute zero, temperature 0 oK -273.15 oC
Acceleration of gravity at earth's surface g 9.81 m/s2 32.2 ft/s2
Atmospheric pressure at sea level 1.013 25 *105 N/m2 14.69 lb/in2
Atomic mass unit 1.660 540 *10-27 kg 1.000 u
Avogadro's constant NA 6.022 141*1023 mol-1
Base of natural logaritms e 2.718 281 828...
Base of natural logaritms lnx 2.3026 log x
Bohr magneton μB e h/4πme 9.274 009 994 *10-24 Am2 5.788 381 *10-5 eV/T
Bohr radius a0 ε0h2/π mee2 5.291 772 106 7* 10-11 m 2.08 *10-9 in
Boltzmann constant k R/NA 1.380 648 52 *10-23 J/K 8.617 330 *10-5 eV/K
Charge of electron e 1.602 176 *10-19 C
Faraday constant F e NA 9.6 485332 89 * 104 C/mol 26.801 Ah/mol
Fine structure constant α 7.297 20* 10-3
Gas constant (molar, ideal) R 8.314 459 8 J/molK 82.057 338 cm3atm/molK
Gravitational constant G 6.674 08 *10-11 m3/kg s2
Mass of electron (rest mass) me 9.109 383 56 *10-31 kg 5.485 799*10-4 u
Mass of neutron mn 1.674 927 47* 10-27 kg 1.008 664 915 u
Mass of proton mp 1.672 621 90 *10-27 kg 1.007 276 466 u
Permeability of a vacuum μ0 4p *10-7 kg m/s2A2
Permittivity of a vacuum ε0 1/μ0 c02 8.854 187 817 *10-12 C2/Nm2 A2s4/kg m3
Planck's constant h 6.626 070 040 * 10-34 J s 4.135 667 *10-15 eV s
Radiation constant, first C1 2 π h c2 3.741 844 *10-16 Wm2
Radiation constant, second C2 h c/k 1.438 833 *10-2 mK
Ratio of a circle's circumference(C) to its diameter π C/d 3.141 592 653…
Rydberg constant R∞ mee4/8ε02h3c0 1.097 373 156 * 107 m-1
Speed of light in vacuum c0 2.99 792 458 *108 m/s
Stefan-Boltzmann constant σ 5.670 367*10-8 W/m2K4 11.7 *10-8 cal/cm2dayK4
Volume ideal gas, 1 atm, 0°C Vm 22413.6 cm3/mol 22.4136 liter/mol
Volume ideal gas,1 atm, 25°C Vm 24466.1 cm3/mol 1.0244651 m3/mol

## Related Topics

• ### Basics

Basic engineering data. SI-system, unit converters, physical constants, drawing scales and more.

## Related Documents

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The mathematical π constants.
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## Citation

• The Engineering ToolBox (2010). Physical Constants . [online] Available at: https://www.engineeringtoolbox.com/physical-constants-SI-d_1662.html [Accessed Day Month Year].

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8.21.8

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