Electric Constant

electric constant [i¦lek·trik ′kän·stənt]

(electricity)

The permittivity of empty space, equal to 1 in centimeter-gram-second electrostatic units and to 10⁷/4πc²farads per meter or, numerically, to 8.854 × 10^-12farad per meter in International System units, wherecis the speed of light in meters per second. Symbolized ε₀.

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Electric Constant 

(or permittivity of free, or empty, space), the constant of proportionality ∊₀ in Coulomb’s law, which gives the force of interaction between two point charges at rest.

In the International System of Units (SI), ∊₀ = 10 ⁷/4πC ² farads per meter (F/m) = 8.85418782 ± 0.00000007 F/m, where c is the speed of light in m/sec. In the centimeter-gram-second (cgs) electrostatic system and in the Gaussian system, ∊₀ is taken to be a dimensionless factor equal to unity.

In contrast to the dielectric constant ∊, which depends on the type of substance, temperature, pressure, and other parameters, the electric constant ∊₀ depends only on the choice of a system of units.