A positive point charge q is placed off center inside an uncharged metal sphere insulated from the ground as shown.Where is the induced charge density greatest in magnitude and what is its sign?

Question

Quizplus · Accepted Answer

The positive point charge q will induce negative charge on the surface of the metal sphere which is closest to it, and positive charge on the surface which is farthest from it. This is because like charges repel and opposite charges attract each other, and the electrons in the metal are free to move due to its metallic nature. 
Since the induced charge is negative near the positive point charge, choice A) A is correct. Additionally, this induced negative charge will be closer to the positive point charge compared to any other point on the surface of the sphere, hence it will have the greatest magnitude of charge density compared to anywhere else on the sphere.

A Positive Point Charge Q Is Placed Off Center Inside