Question

A scientist wipes a rubber rod with a wool cloth which leads to a negative charge on the rod. After this, the scientist touches the rod to a neutral metal sphere. This will transfer the negative charges from the rod to the sphere:



Which statement explains what will happen to the negative charge, and why?

(1 point)
Responses

It will only spread to the air around the sphere, because negative charges need to occupy a big area.
It will only spread to the air around the sphere, because negative charges need to occupy a big area.

It will slowly move to the bottom of the sphere, because the charges are heavy and will sink to the bottom.
It will slowly move to the bottom of the sphere, because the charges are heavy and will sink to the bottom.

It will spread uniformly over the surface of the sphere, because of the conducting nature of the sphere and similar charges push away from each other.
It will spread uniformly over the surface of the sphere, because of the conduc

Answer 1

It will spread uniformly over the surface of the sphere, because the sphere is a conductor and the like charges repel and move to the outer surface. By symmetry on a sphere the surface charge density is the same everywhere, and excess electrons reside on the conductor's outer surface (they do not “sink” or pile up in the air).