Physical Constants

Physical constants are fundamental, universal constants that represent physical quantities. COMSOL Multiphysics includes the most widely used physical constants as built-in constants. Table 5-7 lists all supported physical constants with their names, symbol (variable name), value, and SI unit. The values are taken from Ref. 1 and include the SI unit.

Table 5-7: Physical Constants
Name	Symbol	Value
Acceleration of gravity	g_const	9.80665[m/s^2]
Avogadro constant	N_A_const	6.02214076e23[1/mol]
Boltzmann constant	k_B_const	1.380649e-23[J/K]
Characteristic impedance of vacuum (impedance of free space)	Z0_const	376.730313461...[ohm] (mu0*c)
Electron mass	me_const	9.10938356e-31[kg]
Elementary charge	e_const	1.602176634e-19[C]
Faraday constant	F_const	96485.33289[C/mol]
Fine-structure constant	alpha_const	7.2973525664e-3
Gravitational constant	G_const	6.67408e-11[m^3/(kg*s^2)]
Molar volume of ideal gas (at 273.15 K and 1 atm)	V_m_const	22.413962e-3[m^3/mol]
Neutron mass	mn_const	1.674927471e-27[kg]
Permeability of vacuum (magnetic constant)	mu0_const	2alpha_consth_const/c_const/e_const/e_const (H/m)
Permittivity of vacuum (electric constant)	epsilon0_const	1/mu0_const/c_const/c_const (F/m)
Planck’s constant	h_const	6.62607015e-34[J*s]
Planck’s constant over 2 pi	hbar_const	1.05457180e-34[J*s]
Proton mass	mp_const	1.672621898e-27[kg]
Speed of light in vacuum	c_const	299792458[m/s]
Stefan-Boltzmann constant	sigma_const	5.670367e-8[W/(m^2*K^4)]
Universal gas constant (molar gas constant)	R_const	8.3144598[J/(mol*K)]
Wien displacement law constant	b_const	2.8977729e-3[m*K]