Variables commonly used in physics

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Symbol Meaning SI Unit of Measure
a acceleration meter per second squared (m/s²) or (ms-2)
\mathbf{B} magnetic flux density
also called the magnetic field density or magnetic induction		 tesla (T), or equivalently,
weber per square meter (Wb/m²)
\mathbf{D} electric displacement field
also called the electric flux density		 coulomb per square meter (C/m²)
d distance meter (m)
impact parameter meter (m)
d\mathbf{A} differential vector element of surface area A, with infinitesimally

small magnitude and direction normal to surface S

 square meter (m²)
dV differential element of volume V enclosed by surface S cubic meter (m³)
\mathbf{E} electric field volt per meter (V/m)
e eccentricity unitless
\mathbf{F} force newton (N)
f frequency hertz (Hz)
G the gravitational constant newton meter squared per kilogram squared (N m²/kg²)
\mathbf{H} magnetic field strength
also called just magnetic field		 ampere per meter (A/m)
H Hamiltonian joule (J)
h Planck's constant joule second (J s)
\hbar reduced Planck's constant (\textstyle{\frac h {2\pi}}) joule second (J s)
I action joule second (J s)
intensity watt per square meter (W/m²)
electric current ampere (A)
i Cartesian x-axis basis unit vector unitless
intensity watt per square meter (W/m²)
\mathbf{J} free current density,
not including polarization or magnetization currents bound in a material		 ampere per square meter (A/m²)
j Cartesian y-axis basis unit vector unitless
K kinetic energy joule (J)
k Cartesian z-axis basis unit vector unitless
Boltzmann constant joule per kelvin (J/K)
L inductance henry (H)
luminosity watt (W)
M magnetization ampere per meter (A/m)
moment of force
often simply called moment or torque		 newton meter (N m)
m mass kilogram (kg)
N normal vector unit varies depending on context
atomic number unitless
n refractive index unitless
principal quantum number unitless
P power watt (W)
\mathbf{p} momentum kilogram meter per second (kg m/s)
pressure pascal (Pa)
Q Electric Charge coulomb (C)
q electric charge coulomb (C)
R Electrical resistance ohm (Ω)
Ricci tensor unitless
radiancy
r radius of rotation or distance between two things such as the masses in Newton's law of universal gravitation meter (m)
s arc length meter (m)
T period second (s)
Thermodynamic Temperature
also called absolute temperature		 kelvin (K)
t time second (s)
\mathbf{U} four-velocity meter per second (m/s)
U potential energy joule (J)
u relativistic mass kilogram (kg)
energy density joule per cubic meter (J/m³) or joule per kilogram (J/kg) depending on the context
V voltage
also called electric potential difference		 volt (V)
\mathbf{v} velocity meter per second (m/s)
α angular acceleration radian per second squared (rad/s²)
β velocity in terms of the speed of light c unitless
γ Lorentz factor unitless
\nabla\cdot the divergence operator
often pronounced "del dot"		 per meter (m-1)
\nabla\times the curl operator
often pronounced "del cross"		 per meter (m-1)
ε permittivity farad per meter (F/m)
η efficiency unitless
coefficient of viscosity
also called simply viscosity		 pascal second (Pa s)
θ angular displacement radian (rad)
Κ torsion coefficient
also called torsion constant		 newton meter per radian (N m/rad)
Λ cosmological constant per second squared (s-2)
λ wavelength meter (m)
\mathbf{\mu} magnetic moment ampere square meter (A m²)
ν frequency hertz (Hz)
ρ mass density
usually simply called density		 kilogram per cubic meter (kg/m³)
freeelectric charge density,
not including dipole charges bound in a material		 coulomb per cubic meter (C/m³)
τ torque newton meter (N m)
Φ field strength unit varies depending on context
Ψ wave function unitless
ω angluar frequency or angular speed radian per second (rad/s)

[edit] See also