Static Electricity: Coulomb's Law

Coulomb's LawThe electrostatic force between two point charges is proportional to the product of their charges and inversely proportional to the square of the distance between them

History This law was first published in 1785 by French physicist Charles Augustin de Coulomb it is analogous to Isaac Newton's inverse-square law of universal gravitation

F∝ (Q₁)(Q₂)/d² Q₁ = charge on body one Q₂ = charge on body two d = distance between them

This is the formula used for numerical calculations ε = permittivity of the medium (surrounding the charges) r = distance between the charges When dealing with spherical conductors, the distance is the distance between the centres of the spheres

The electrostatic force can be either attractive or repulsive

Permittivity If the permittivity is low, the force is big The force is greatest when the charges are in a vacuum ε₀ = permittivity of a vacuum All media have a greater permittivity than that of a vacuum = the relative permittivity (εᵣ) ε = εᵣ ε₀

Direction of the Force The direction of the force is always along the line joining the two charges Force is attractive if the charges are opposite Force is repulsive if the charges are the same

New Page