F = k {( |q1|*|q2| ) / R2 }

Where F is the electrostatic force of attraction or repulsion between two charged particles (point charges).
q1 and q2 represent the point charges, which may be negative or positive.
R is the separation between the two points.
k is a constant, where k = 8.99x109 (N*m2)/C2 (Newtons)(meters squared) over (Coulombs squared)

Note the similarities Coulomb's Law and Newton's Law of Gravitation
An alternative representation to 0x45's rendition of Coulomb's law accounts for the polarizability of the environment:

                q1 q2
          f = ----------
              4 pi E r2

Where E is actually epsilon. E/E0 is known as the dielectric constant, or relative permittivity. E0 is the permittivity of free space (of a vacuum).

The dielectric constant, subsumed in the constant k in the previous writeup, accounts for screening of electrostatic interactions between charges by the environment. An environment that is highly polarizable will orient around a given charge, thereby effectively neutralizing the effects of electric field at long distances. Water has a high dielectric constant - around 80. As a result, ions in water have a much weaker attraction or repulsion than they do in the gas phase.

Cou`lomb's" law (?). (Physics)

The law that the force exerted between two electric or magnetic charges is directly proportional to the product of the charges and inversely to the square of the distance between them.


© Webster 1913

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