The statement "the electric force of repulsion or attraction between two point charges is directly proportional to the product of the charges and inversely proportional to square of the distance between them" refer to
A point charge A of charge +4μC and another B of charge -1μC are placed in air at a distance 1 m apart. Then the distance of the point on the line joining the charge B, where the resultant electric field is zero, is (in m)
Two point charges A and B separated by a distance R attract each other with a force of 12 x 10-3N. The force between A and B when the charges on them are doubled and distance is halved