Solution
= Solution
<Gauss's law> gives $E=Q\hat r/(4\pi\varepsilon_0r^2)$ outside any spherically symmetric charge distribution. The shell in (ii) has $Q=2\pi\rho_0(b^2-a^2)$, and differentiating its exterior potential gives exactly this field.
= Solution
<Gauss's law> gives $E=Q\hat r/(4\pi\varepsilon_0r^2)$ outside any spherically symmetric charge distribution. The shell in (ii) has $Q=2\pi\rho_0(b^2-a^2)$, and differentiating its exterior potential gives exactly this field.