A spherical volume of radius,(adsbygoogle = window.adsbygoogle || []).push({}); a, is filled with charge of uniform density,p. We want to know the potential energy,U, of this sphere of charge, that is, the work done in assembling it. Calculate it by building the sphere up layer by layer, making use of the fact that the field outside a spherical distribution of charge is the same as if all the charge were at the center. Express the result in terms of the total charge,Q, in the sphere.

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# Homework Help: Potential energy - Purcell

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