Question

State the limitation of Coulomb's law of electrostatics

Answer 1

Coulomb’s Law is an action-at-a-distance inverse square law of force between two charges. It is very, very accurate for stationary charges. However, we know that if one charge moves, the response at the other charge cannot be instantaneous (as Coulomb’s Law would imply) as it cannot be transmitted more rapidly than at the speed of light.

Action at a distance was felt to be unsatisfactory (despite its excellent predictions of forces between charges) – how can one object influence another without any connecting medium?

This among other considerations motivated James Clerk Maxwell to incorporate Coulomb’s Law along with the other known laws of electricity and magnetism into a mathematical theory in terms of electric and magnetic fields, rather than forces acting at a distance. This theory accurately predicts the forces (both electric and magnetic) between moving charges, as well as uncovering the nature of light as an electromagnetic radiation and predicting other electromagnetic radiations such as radio.

So the limitations of Coulomb’s Law are

a) it doesn’t deal with moving charges

b) it is an unsatisfactory action-at-a-distance explanation.

Note that Newton’s gravitational law is also action-at-a-distance; and was also (inspired by Maxwell) replaced by Einstein with a theory in terms of fields.

Answer 2

Answer:

• The law is applicable only for the point charges at rest.

• Coulomb’s Law can be only applied in those cases where the inverse square law is obeyed.
• It is difficult to implement Coulomb’s law where charges are in arbitrary shape because in such cases we cannot determine the distance’ between the charges.
• Coulomb's law does not apply to two charged bodies of finite sizes, say two charged spheres. It is because, the distribution of charge does not remain uniform, when the two bodies are brought together.
• The electric charges must be stationary.
• We can use the formula if the charges are static ( in rest position)
• The formula is only valid when the solvent molecules between the particle are sufficiently larger than both the charges