Physics Constants

This table contains a number of physical constants often used in physics and engineering.

Quantity Symbol Value SI Units Cgs Units
Velocity of light c 2.9979250 108 m/sec 1010 cm/sec
Free space permittivity eo 8.8541 10-12 F / m 10-14 F / cm
Free space permeability mo 1.2566 10-6 H / m 10-8 H / cm
Fine-structure constant a 7.297351 10-3 10-3
Electron charge e 1.6021917 10-19 C 10-20 emu
Planck’s constant h 6.626196 10-34 J-sec 10-27 erg-sec
Avogadro’s number N 6.022169 1026 kmole-1 1023 mole-1
Atomic mass unit amu 1.660531 10-27 kg 10-24 gm
Electron rest mass me 9.109558 10-31 kg 10-28 gm
Proton rest mass Mp 1.672614 10-27 kg 10-24 gm
Neutron rest mass Mn 1.674920 10-27 kg 10-24 gm
Proton / electron mass ratio Mp / me 1836.109
Electron charge / mass ratio e / me 1.7588028 1011 C / kg 107 emu / gm
Faraday constant F 9.648670 107 C / kmole 103 emu / mole
Rydberg constant R 1.09737312 107 m-1 105 cm-1
Boltzman constant K 1.3807 10-23 J / K 10-16 erg / K
Stefan-Boltzman constant s 5.671 10-8 W / m2 K4 10-5 W / cm2 K4
Gravitational constant g 9.8067 kg m / s2 105 gm cm / s2
Loschmidt constant no 2.6868 1025 m-3 1019 cm-3
Bohr radius ao 5.2917715 10-11 m 10-9 cm
Classical electron radius ro 2.817939 10-15 m 10-13 cm
Standard atmosphere atm 1.0132 x 105 Pa 1.0125 x 106 erg / cm3

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