Coulomb’s law and its limitations


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.

That is,

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.

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