A student rubs a rubber rod with fur, producing a negative charge on the rod. The student then touches the rod to a hollow, neutral metal sphere that stands on an insulating plastic stand. This transfers negative charges from the rod to the sphere. Which statement best predicts what will happen to the charge, and why?
A. It will quickly spread to the air around the sphere, because it will seek to occupy as large a volume of neutral matter as possible.
B. It will remain at the point of contact between the rod and the sphere, because resistance in the metal prevents the charges from easily moving.
C. It will distribute itself evenly over the surface of the sphere, because like charges repel and the sphere is a conductor.
D. It will slowly drift to the bottom of the sphere, because the charges rapidly attach to individual atoms, making them slightly heavier than surrounding atoms.
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C. It will distribute itself evenly over the surface of the sphere, because like charges repel and the sphere is a conductor.
In a conducting object, like the metal sphere, charges are free to move and redistribute themselves. Since like charges repel each other, the negative charges on the sphere will repel each other and spread out as evenly as possible over the surface of the sphere. This ensures that they are as far apart from each other as possible, minimizing their repulsive forces.