Physics 1028 Study Guide - Final Guide: Mechanical Equilibrium, Electric Field
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Initially, there is no electrostatic force since sphere b doesn"t carry a charge. After connecting both spheres, the mutual repulsion of the mobile positive charges on sphere a leads to a maximum charge separation, given when qa = q/2 and qb = q/2. At this point we make a less obvious assumption: we assume that the uniformity of the charge dis- tribution on either sphere is not disturbed by the other sphere. This assumption is reasonably justified as long as the sizes of the two spheres are small in comparison to their distance. When this assumption is valid, the entire charge on either sphere behaves as if it were a point charge at the centre of the sphere. Note that we would have to consider all the individual point charges on each sphere separately without this assumption. Using coulomb"s law we find for the magnitude of the force between the two spheres: (1)
