Electric

Gravitational

q (charge)

m (mass)

$\varrho$ (volume charge density)

$\varrho$ (volume mass density)

σ (surface charge density)

σ (surface mass density)

λ (line charge density)

λ (line mass density)

φ (scalar potential)

φ (scalar potential)

$A$ (vector potential)

$A$ (vector potential)

$J$ (convection current density)

$J$ (mass-current density)

I (electric current)

I (mass current)

$E$ (electric field)

$g$ (gravitational field)

$B$ (magnetic field)

$K$ (cogravitational field)

${\epsilon }_0$ (permittivity of space)

$-1/4\text{π}G$

${\mu }_0$ (permeability of space)

$-4\text{π}G/c^2$

$-1/4\text{π}{\epsilon }_0$ or $-{\mu }_0{c}^2/\text{4π}$

G (gravitational constant)