Consider a spherical capacitor, as shown in Fig. 4.4. The capacitor comprises: A solid sphere made from a perfect conductor with center 0 and radius Ri; a perfectly conducting shell with center 0, zero thickness, and radius Ri; a dielectric shell with dielectric constant E1, center 0, inner radius R2, and outer radius R3 (i.c., of thickness (R3-R2)); the rest is vacuum. Note that R;