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