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:

Question

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.

Answer 1

The correct statement is:

C. It will distribute itself evenly over the surface of the sphere, because like charges repel and the sphere is a conductor.

Explanation: When the negatively charged rubber rod comes into contact with the neutral metal sphere, negative charges (electrons) move from the rod onto the sphere. Since the metal sphere is a conductor, the negative charges will repel each other and distribute themselves evenly across the surface of the sphere due to the principle that like charges repel. Additionally, the charges will spread out to minimize the electric potential energy, achieving an equilibrium where the charge is evenly distributed over the surface of the conductive material.