Two insulating small spheres are rubbed against each other and placed 1 cm apart. Calculate the number of electrons transferred from one sphere to another if they attract each other with a force of 0. 1N.

Let the number of electrons transfered be n.According to coulomb's law force between two charges is given by,F=kq1q2r2hence, the magnitude of force between the given two spheres will be⇒F=kq2r2=0.1⇒9×109×n×1.6×10−1920.012=0.1⇒n×1.6×10−19=13×107⇒n=14.8×1012≈2×1011