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A spherical capacitor has inner radius $a$ and outer radius $b$

a) Find (derive!) its capacitance of this arrangement. Show All Work!

b) Show that when $b = a + \delta$ with $\delta \ll a$ the capacitance has the limiting form $C = \epsilon_0 A/\delta$ where $A$ is the area of the inner sphere and $\delta$ is the separation of the shells.