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:
Charged Rubber Rod
Metal Sphere
Insulating Plastic Stand
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.
The correct answer is C: it will distribute itself evenly over the surface of the sphere, because like charges repel and the sphere is a conductor.
When the charged rubber rod touches the neutral metal sphere, the negative charges on the rod will repel the negative charges in the metal sphere. As a result, the negative charges will distribute themselves evenly over the surface of the sphere to minimize their repulsion. This is because like charges repel each other and try to move as far away from each other as possible. Additionally, since the metal sphere is a conductor, the charges are free to move around the surface of the sphere.
Option A is incorrect because negative charges will not spread to the air around the sphere. Option B is incorrect because resistance in the metal does not prevent charges from easily moving in a conductor. Option D is incorrect as charges do not attach to individual atoms or make them slightly heavier than surrounding atoms.