The 12 Important Physical Constants

Speed of light

Speed of light tells us how fast light travels in empty space (vacuum).

$$ \begin{align} c ~=~ 299 \, 792 \, 458 \, \frac{\mathrm m}{ \mathrm s} \end{align} $$

The elementary charge is the smallest, freely existing electric charge in our universe.

$$ \begin{align} e ~=~ 1.602 \, 176 \, 634 ~\cdot~ 10^{-19} \, \mathrm{C} \end{align} $$

The vacuum permeability appears in equations that deal with magnetic fields.

$$ \begin{align} \mu_0 ~\approx~ 1.256 \, 637 \, 062 ~\cdot~ 10^{-6} \, \frac{\mathrm{Vs}}{\mathrm{Am}} \end{align} $$

The vacuum permittivity occurs in equations that deal with electric fields.

$$ \begin{align} \varepsilon_0 ~\approx~ 8.854 \, 187 \, 8128 ~\cdot~ 10^{-12} \, \frac{\mathrm{As}}{\mathrm{Vm}} \end{align} $$

The Planck's constant, is a physical constant that appears in equations whenever the equation describes quantum effects.

$$ \begin{align} h ~=~ 6.626 \, 070 \, 15 ~\cdot~ 10^{-34} \, \mathrm{Js} \end{align} $$

The gravitational constant occurs in Newton's law of gravity and Einstein field equations, which describe the interaction between masses.

$$ \begin{align} G ~\approx~ 6.674 \, 30 ~\cdot~ 10^{-11} \, \frac{ \mathrm{m}^3 }{ \mathrm{kg} \, \mathrm{s}^2 } \end{align} $$

The Boltzmann constant occurs in equations which describe systems with many particles.

$$ \begin{align} k_{\text B} ~=~ 1.380 \, 649 ~\cdot~ 10^{-23} \, \frac{\mathrm{J}}{\mathrm{K}} \end{align} $$

The mass of one electron

$$ \begin{align} \class{brown}{m_{\text e}} ~\approx~ 9.109 \, 383 \, 701 \, 5 ~\cdot~ 10^{-32} \, \mathrm{kg} \end{align} $$

Mass of one proton

$$ \begin{align} \class{brown}{m_{\text p}} ~\approx~ 1.672 \, 621 \, 923 \, 69 ~\cdot~ 10^{-27} \, \mathrm{kg} \end{align} $$

Mass of one neutron

$$ \begin{align} \class{brown}{m_{\text n}} ~\approx~ 1.674 \, 927 \, 498 \, 04 ~\cdot~ 10^{-27} \, \mathrm{kg} \end{align} $$

The Avogadro constant indicates how many particles are present in one mole.

$$ \begin{align} N_{\text A} ~=~ 6.022 \, 140 \, 76 \cdot 10^{23} \, \frac{1}{\mathrm{mol}} \end{align} $$

The (universal) gas constant occurs in thermodynamics - in the description of gases (e.g. air).

$$ \begin{align} R ~=~ 8.314 \, 462 \, 618 \, 153 \, 24 \, \frac{\mathrm{J}}{ \mathrm{K} \, \mathrm{mol} } \end{align} $$