REVIEW OF CLASSICAL ELECTRODYNAMICS

We now recognize that many apparently unrelated physical 

In these equations D is the electric displacement and B the magnetic induction, while E and H axe the electric and magnetic fields. The electric charge density is given by P. 

Maxwell observed that the equations are inconsistent in this present form if J is identified with the ordinary current density J. This is easily proved by taking the divergence of both sides of equation (2.4) and recalling that div curl of any vector is identically zero. This leads to the equation div J = 0 and if J = J, this would conflict with the equation of continuity 

In macroscopic media Maxwell s equations must be supplemented by the constitutive relations which enable the average effect of a large number of atoms to be taken into account without requiring detailed knowledge of the response of individual atoms to the effects of electric and magnetic fields. For an isotropic permeable conducting dielectric these relations are of the form  

In the M.K.S. system, is called the permittivity of free space and is experimentally determined to have the value 

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