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:

image 63f9196b581c4f17bbe56cfd6ddd781f

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

(1 point)
Responses

It will remain only on one spot of the sphere, because the low conductivity of the metal prevents the charges from spreading out.
It will remain only on one spot of the sphere, because the low conductivity of the metal prevents the charges from spreading out.

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

Answer 1

It will spread uniformly over the surface of the sphere, because the sphere is a conductor and the free electrons move until they are as far apart as possible. In electrostatic equilibrium the electric field inside a conductor is zero, so excess charge resides on the outer surface; symmetry of a sphere makes that surface charge distribute uniformly.