Coulomb's law states that the force between two point charges is inversely proportional to the square of their distance.

If we have two charges of q_{1} coulombs and q_{2} coulombs which are d metres apart, then the Coulomb force, F,
can be calculated by
F=kq_{1}q_{2}/d^{2}
where k is Coulomb's constant.

If the result is negative then the charges attract each other, otherwise they repel.

Fischer-Cripps. A.C., *The Electronics Companion.* Institute of Physics, 2005.

Copyright © 2014 Barry Watson. All rights reserved.