Coulomb's Law

       Coulomb is a unit of charge (q), named after a French physicist - Charles Augustin de Coulomb. When two charged particles are placed near each other, they exert force on each other. The intensity and type of force (attractive or repulsive) depend on placement of particles & type of charge (positive or negative) on particles, respectively. This law, therefore, explains behaviour of two charges or charged particles and gives the relationship of force acting between them when they are placed under the electrostatic force field of each other. There are two statements under Coulomb's law ;

Coulomb's 1st Law

First Law of Coulomb ;  

       This law says that same kind of charges repel each other whereas opposite kind of charges attract each other i.e., positive charge creates repulsive force or push force on positive charge and negative charge also creates repulsive force or push force on negative charge whereas positive charge attracts negative charge and vice versa.

Coulomb's 2nd Law

Second Law of coulomb ;

       This law says that the intensity of force acting between two charges is directly proportional to the product of individual charges, indirectly proportional to the square of distance between them and also depends on the medium.

Let,

                F    =    Force in Newton
                q₁  =    Charge on one particle in Coulombs
                q₂  =    Charge on another particle in Coulombs

=>

       where, K is constant of proportionality or coulomb’s constant, which depends on surrounding medium.

       where, Ɛ0  is permittivity of vaccum or air whose value is 8.854 X 10 ^-12 Farad / meter.

               &, Ɛm  is the relative permittivity of the medium containing charges with respect to free space.