Physical Constants & Units Conversion
A. Miyoshi

Physical Constants & Units Conversion

Physical Constants (CODATA 2014) and SI Units

Previous physical constants   2006   2010
Here, a brief summary of physical constants based on   P.J. Mohr, B.N. Taylor, and D.B. Newell (2015), "The 2014 CODATA Recommended Values of the Fundamental Physical Constants" (Web Version 7.0). This database was developed by J. Baker, M. Douma, and S. Kotochigova. Available: http://physics.nist.gov/constants [Wednesday, 07-Oct-2015 01:28:43 EDT]. National Institute of Standards and Technology, Gaithersburg, MD 20899.   is shown. For detail, see, Fundamental Physical Constants from NIST.

Mathematical Constant

π 3.14159265358979323846

Fundamental Physical Constants (2014 CODATA)

Value UnitRel. std.
uncert.
Quantity
c0 299 792 458
= 2.997 924 58×108
m s−1(exact) speed of light
in vacuum
h 6.626 070 040(81)×10−34 J s1.2×10−8 Planck constant
e 1.602 176 6208(98)×10−19 C6.1×10−9 elementary charge
NA 6.022 140 857(74)×1023 mol−11.2×10−8 Avogadro constant
me 9.109 383 56(11)×10−31 kg1.2×10−8 electron mass
R 8.314 4598(48) J K−1 mol−1 5.7×10−7 molar gas constant
G 6.674 08(31)×10−11 m3 kg−1 s−2 4.7×10−5 Newtonian constant
of gravitation

Physical Constants

- though with an apparent relation to fundamental constants, known more accurate than derived from them

Derived as Value Unit Rel. std.
uncert.
Quantity
R mec0α2 / 2h 10 973 731.568 508(65)
= 1.097 373 156 8508(65)×107
m−1 5.9×10−12 Rydberg constant
α μ0c0e2 / 2h 7.297 352 5664(17)×10−3 2.3×10−10 fine structure
constant
F NAe 96 485.332 89(59)
= 9.648 533 289(59)×104
C mol−16.2×10−9 Faraday constant
μB eh / 4πme 927.400 9994(57)×10−26 J T−16.2×10−9 Bohr magneton

Physical Constants

- derived from fundamental mathematical / physical constants

Derived as Value Unit Rel. std.
uncert.
Quantity
μ0 4π×10−7 ~ 12.566 370 614×10−7 H m−1
(N A−2)
(exact) magnetic constant
ε0 1 / μ0c02 ~ 8.854 187 818×10−12 F m−1(exact) electric constant
ħ h / 2π 1.054 571 800(13)×10−34 J s1.2×10−8
mu 10−3 / NA 1.660 539 040(20)×10−27 kg1.2×10−8 atomic mass constant
k R / NA 1.380 648 52(13)×10−23 J K−15.7×10−7 Boltzmann constant
a0 α / 4πR 0.529 177 210 67(12)×10−10 m2.3×10−10 Bohr radius
Eh 2Rhc0 4.359 744 650(54)×10−18 J1.2×10−8 Hartree energy

SI Derived Units with Special Names

Derived QuatitySymbol Expression
in terms of
other SI units
Expression
in terms of
SI base units
electric chargeC A s
electric potentialV J C−1m2 kg s−3 A−1
electric capacitanceF C V−1m−2 kg−1 s4 A2
Celsius temperature °C θ / °C + 273.15 ≡ T / K

Conversion of Units

Non-SI Units

Quantity
pressure 1 bar ≡ 105 Pa
1 atm ≡ 101 325 Pa
1 Torr ≡ 1 / 760 atm ~ 133.322 3684 Pa
energy1 cal ≡ 4.184 J
cross section1 b (barn) ≡ 1 × 10−28 m2