| scalar constant linking the electric quantities and the mechanical quantities, obtained from the relation
based on Coulomb's law in a vacuum, where F is the magnitude of the force between two particles with electric charges Q1 and Q2 respectively, placed at a distance r apart
Note 1 to entry: In a vacuum, the product of the electric constant ε0 and the electric field strength E is equal to the electric flux density D:
D = ε0E
Note 2 to entry: The electric constant ε0 is related to the magnetic constant μ0 and to the speed of light in vacuum c0 by the relation
ε0μ0c02 = 1.
Note 3 to entry: The value of the electric constant ε0 is equal to