Coulomb's Law

Where is a point charge. The electric field intensity of a positive point charge is in the outward radial direction and has a magnitude proportional to the charge and inversely proportional to the square of the distance from the charge. It means if we have an electric field caused by a positive point charge. Then we can measure the strength of that field at different distance, which is the R. The further we measure the strength, the great become R, and the less become the strength of that field at the particular place. When a charge is not at the center of a coordinate, we can use the following equations: since , therefore we have: