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Coulomb's Law of force between charges

The force between two charges Q1 and Q2 separated by a distance d is expressed by Coulombs law:

Coulomb's law for the force (F) between two charges: F = (1/4pe)Q1Q2/d2

where e is a constant for a given material known as the permittivity of that material. Changing e changes the force between the two charges, for example if e is large the force is small.

In a vacuum this equation becomes

Coulomb's law for the force (F) between two charges in a vacuum:
F = (1/4peo)Q1Q2/d2

where eo is the permittivity of free space (8.84x10-12 Fm-1)

Notice that this force is:
(a) proportional to 1/d2
(b) dependent on the electrical properties of the material between the charges (e)
(c) it may be attractive or repulsive

© Keith Gibbs 2011