This is merely an alternative form of Coulomb’s law as given in Eq. (3.13). However, this form is conceptually different: is viewed as the source of the electric field intensity and this electric field intensity exerts a force on . We must hasten to say that this is only a convenience. It is equally acceptable to view as the source of the field and the force is then exerted on . This symmetry is again due to the fact that the magnitude of the force on each charge (but not the direction) is the same.