State and explain Coulomb's incerse square law in electricity.

Explanation

Coulomb's law - Statement: Force between two charges is proportional to the product of the charges and inversely proportional to the square of the distance between them. The force acts along the straight line joining the two charges.
Explanation : Let us consider two charges `q_(1)` and `q_(2)` be sepqrated by a distance r.
Then `F alpha q_(1) q_(2)` and `F prop 1/r^(2)` or `F prop (q_(1)q_(2))/r^(2)`
`:. F=1/(4pi epsi_(0)). (q_(1)q_(2))/r^(2)` where `1/(4pi epsi_(0))=9xx10^(9) Nm^(2) C^(-2)`.
In vector form, in free space `vec(F)=1/(4 pi epsi_(0))(q_(1)q_(2))/r^(2) hat(r)`. Here `hat(r)` is a unit vector.
`epsi_(0)` is called permittivity of free space.
`epsi_(0)=8.85xx10^(-12) C^(2)//N-m^(2)` or Farad/meter.
In a medium, `F_(m)=1/(4pi epsi) (q_(1)q_(2))/r^(2)=1/(4pi epsi_(0) epsi_(r))xx(q_(1)q_(2))/r^(2) [ :' epsi=epsi_(0) epsi_(r)]`
Where `epsi` is called permittivity of the medium.