Dielectric Medium

Coulomb's law defines the force, F, between charged particles q 1 and q 2 at a distance of 'r' in a vacuum as

F = k*(q 1 q 2)/r2, where k is a constant.

To measure the same forces in a non-vacuum, dielectric medium, such as the aqueous environment of biological systems, the dielectric constant () must be taken into account. The dielectric constant arises from the fact that the dielectric medium shields the charges from each other. This modifies Coulomb's law as follows:

F = k*(q 1 q 2)/(*r2)

Thus, the larger the value of , the smaller the force between the charges.

See also: Energy of Interaction