Demonstrate that the law of electric charge conservation, i.e., `grad. J = -del rho//del t`, follows from Maxwell's equactions.

Explanation

From the equction `Curl vec(H) - (del vec(D))/(del t) = vec(j)`
we get on taking divergence of both sides
`- (del)/(del t)` div `vec(D) = di v vec(j)`
But div `vec(D) = rho` and hence div `vec(j) + (del rho)/(del t) = 0`