Similar charge of electricity repel each other ,whereas dissimilar
or unlike charges attract each other.

Second law :

The force exerted by two point charges

Is directly proportional to the product of their
strengths

Is inversely proportional to the square of the
distance between them

Is inversely proportional to the absolute permittivity
of the surrounding medium.

This Law is also know as coulomb’s law and may be expressed mathematically as .

Where K is the constant of proportionality and is equal to

Coulomb or Unit of charge

A coulomb is that quantity of charge of electricity which when placed in air one meter away from an equal and similar charges repel it with a force of 8.987×10^9 Newton.

Electrostatic Triangle

Some definations

Equi-potential surface ;

Equi-potential
surface is a surface in an electric field such that all point on it are at the
same potential.

Potential gradient

Potential gradient is the rate of change of potential with distance measured in the direction of electric force .Electric intensity at a point is equal to the negative potential gradient at that point.

Electrical potential

Electrical potential at any point in an electric field surrounding a charge body is equal to the work done in moving a unit positive charge from a point where the potential is zero to that point where the potential is to be measured against the electrostatic force in the field.

The potential at distance d from q is given by

Electric Intensity

Electric intensity at any point in the field space around the charge is measured by the force which will act on a unit positive charge place at that point .Thus

I am Hussain Syed from Pakistan .i am electrical engineer by profession and working with a well reputed organization which is related to electrical technology .