Question

A parallel-plate capacitor is formed by two discs with a uniform poorly conducting medium between them. The capacitor was initially charged and then disconnected from a voltage source. Neglecting the edge effects, show that there is no magnetic field between capacitor plates.

Answer 1

Here also we see that neglecting edge effects, $$\vec {j_{d}} = -\vec {j}$$. Thus Maxwell's equations reduced to, div $$\vec {B} = 0, Curl\ \vec {H} = 0, \vec {B} = \mu \vec {H}$$
A general solution of this equation is $$\vec {B} = constant = \vec {B}_{0}\cdot \vec {B}_{0}$$ can be thought of as an extraneous magnetic field. If it is zero, $$\vec {B} = 0$$.