(a) To calculate the "capacitance" of an isolated sphere, evaluate the result we obtained in Example 26.4 in the limit that \(R_{2}\) goes to infinity.

(b) What is the capacitance of the spherical metal dome of a Van de Graaff generator that has a radius of about \(2.5 \mathrm{~m}\).

(c) Given that air breaks down in an electric field with a magnitude of about \(3.0 \times 10^{6} \mathrm{~V} / \mathrm{m}\), what is the maximum amount of charge that can be stored on the dome before the air breaks down?

Data from Example 26.4

What is the capacitance of a spherical capacitor consisting of two concentric conducting spherical shells of radii \(R_{1}\) and \(R_{2}>R_{1}\) ?