Problem 3.77

A uniform isotropic dielectric is shaped as a spherical layer with radii \(a\) and \(b\). Draw the approximate plots of the electric field strength \(E\) and the potential \(\varphi\) vs the distance \(r\) from the centre of the layer if the dielectric has a certain positive extraneous charge distributed uniformly: (a) over the internal surface of the layer; (b) over the volume of the layer.