problem23_73

University Physics with Modern Physics with Mastering Physics (11th Edition)

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23.73: a) The electrical potential energy for a spherical shell with uniform surface charge density and a point charge q outside the shell is the same as if the shell is replaced by a point charge at its center. Since , dr dU F r - = this means the force the shell exerts on the point charge is the same as if the shell were replaced by a point charge at its center. But by Newton’s 3 rd law, the force q exerts on the shell is the same as if the shell were a point charge. But q can be replaced by a spherical shell with uniform surface charge and the force is the same, so the force between the shells is the same as if they were both replaced by point charges at their centers. And since the force is the same
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Unformatted text preview: as for point charges, the electrical potential energy for the pair of spheres is the same as for a pair of point charges. b) The potential for solid insulating spheres with uniform charge density is the same outside of the sphere as for a spherical shell, so the same result holds. c) The result doesn’t hold for conducting spheres or shells because when two charged conductors are brought close together, the forces between them causes the charges to redistribute and the charges are no longer distributed uniformly over the surfaces....
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This document was uploaded on 02/06/2008.

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