posted by BAdams .
I have been unable to find text references for this material in my book:
The problem gives me two spheres, Sphere A has unevenly distributed negative charges, Sphere B has negative charges distributed almost evenly near the edge of the sphere, forming a circle inside the sphere.
Q: The negative charge distribution over the surface of two isolated spheres is dipicted. One of the spheres is made of copper and the other is made of rubber. Identify the sphere that depicts charge distribution of copper and that of rubber. Support the answer with an explanation.
Copper is a conductor, so voltage will be constant on its surface. To get constant voltage, there must be a constant E field at the surface, which means charge is uniformly distributed.
In insulators, one can have any charge distribution.