Electric force

To find force between two static charges a law given by scientist Charles-Augustin de Coulomb in 1784. Which is known as Coulomb's law or Coulomb's inverse square law.

Coulomb's law :-
When two point charge present at a distance then force between them is -

1. Directly proportional to product of charge.
2. Inversely proportional to square of distance between them.

Let two point charge q1 and q2 present at a distance r then
F α q1.q2   ........(1)
F α r²         ........(2)
 now from equation (1) and (2)
F α (q1.q2)/r^{2  ......(3)
F = k(q1.q2) /}r2 N
here k is coulomb's constant.
k = 1/4πε₀  = 9*10^9 Nm^2/c^2
here N = Newton ( unit of force)
ε₀  is permittivity of vacuum = 8.85*10^-12 c^2/N.m^2
Permittivity of vacuum:- It is the capability of vacuum to flow the charges.

Note:-

• Coulomb's force is applicable only for static charge.
• It is applicable for point charges.
• It is low range force.

Point charge:- Charges whose size are very smaller then distance between them called point charge.