Problem 3.203

The radii of spherical capacitor electrodes are equal to \(a\) and \(b,\) with \(a< b .\) The interelectrode space is filled with homogeneous substance of permittivity \(\varepsilon\) and resistivity \(\rho .\) Initially the capacitor is not charged. At the moment \(t=0\) the internal electrode gets a charge \(q_{0}\). Find: (a) the time variation of the charge on the internal electrode; (b) the amount of heat generated during the spreading of the charge.