PHYSICS · Single correct · AP · Physics 2: Algebra-based · Electric Force Field and Potential · Electric Force Field and Potential
Problem
A negatively charged plastic rod is brought near, but does not touch, a small neutral metal ball. While the rod is held in place, the ball is briefly connected to ground with a wire that is removed before the rod is taken away.
Which of the following best explains the sign of the net charge that remains on the metal ball after the rod is finally removed?
(a) The ball remains neutral because the charge induced while the rod is present disappears as soon as the rod is removed.
(b) The ball becomes positively charged because electrons were repelled from the ball to Earth while the negative rod was nearby.
(c) The ball becomes negatively charged because electrons were attracted from Earth to the ball while the negative rod was nearby.
(d) The ball becomes negatively charged because grounding allows positive charges to leave the ball, leaving behind an excess of electrons.