At any point electric field intensity is the total sum of all the electric field intensities generated due to different charges at the same point. If other charges are absent then vectorially sum up their Electric field intensities.
Here is the measure of the distance of the point P between the charge and is the unit vector having the direction same as that of direction of to the point p.
Now let us think that the locations of the point charges q1, q2, q3……., qn in space are r1, r2, r3…….., rn. Now our motive is to calculate the Electric field Intensity at point P whose position is r. The resultant force will be calculated by the formula given below: