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?

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.
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.
It will distribute itself evenly over the surface of the sphere, because like charges repel and the sphere is a conductor.
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 statement that BEST predicts what will happen to the charge is:

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

When a charged object (in this case, the negatively charged rubber rod) comes into contact with a conductor (the hollow metal sphere), the excess negative charges will move throughout the conductor. Because the charges are identical and repel each other, they will spread out uniformly over the surface of the conductor until they are evenly distributed. This phenomenon occurs due to the high mobility of charges in conductive materials, allowing them to respond quickly to the repulsive forces between like charges.