Comparison between the two sets reveals that the only difference is in the last term of Eq. (11.6). This term is a current
density and is called the displacement current density.
Perhaps the easiest way to show that the pre-Maxwell equations are not, in general, adequate is to show that they are not
consistent with the continuity equation or that conservation of charge is not satisfied unless the displacement current density
in Eq. (11.6) is introduced. To do so, we take the divergence on both sides of Eq. (11.2):