Statement. The force of interaction between two stationary point charges q1 and q2 is directly proportional to the product of the charges and inversely proportional to the square of the distance r between them.
F α q1q2/r2
If the charges are placed in vacuum, then
F = 1/4Пεo q1q2/r2
where 1/4Пεo is a proportionality constant.
εo is the permittivity of free space = 8.85418 x 10-12 C2 /Nm2 or Farad/m
Definition of coulomb: One coulomb is defined as the quantity of charge, which when placed 1 metre from an equal and opposite charge in vacuum, repels it with a force of 9.0 x 109 N.
Limitation Of Coulomb’s Law:
It is difficult to apply the law when charges are of arbitrary shape. Here, the distance, r cannot be determined accurately as the centres of arbitrarily shaped charged bodies cannot be identified accurately.