A plastic rod is charged up by rubbing a wool cloth, and brought to an initially neutral metallic sphere that is insulated from ground. It is allowed to touch the sphere for a few seconds, and then is separated from the sphere by a small distance. After the rod is separated, the rod:A) is repelled by the sphere. B) is attracted to the sphere. C) feels no force due to the sphere.

A) is repelled by the sphere.

Explanation:

On rubbing the plastic rod with the wool cloth the rod gains some electrons from the surface of the wool and becomes electrostatically negative in charge.

When this rod is brought near to a neutral metallic sphere then the electrons of the sphere get repelled from the nearest portion of the metallic sphere as it a conductor and the electrons accumulate on the farthest opposite side of the rod.

But when the rod is brought into contact for some time then the from the portion of the rod which is in contact to the sphere loses the electrons from that region to the sphere since plastic is not an electrical conductor so not all the charges travel to the sphere.

Then when the rod is separated, the charges on the sphere spread uniformly and the similar charged rod faces repulsion.

explanation:

v=uf/(u-f)

= 5.-10/(5+10) convex lens has negative focal length