Chapter 5.1, Problem 3eT

In case A at right, a point Charge $+q$ is a distance s from the center of a small ball with charge $+Q$ .

In case B the +q charge is a distance s from the center of an acrylic rod with a total charge $+Q$ .

Consider the following student dialogue:

Student 1: "The charge rod and the charged ball have the same charge, $+Q$, and are the same distance from the point charge, $+q$. So the force on $+q$will be the same in both cases."

Student 2: "No, in case B there are charges spread all over the rod. The charge directly below the point charge will exert the same force on $+q$as the bail in case A. The rest of the charge on the rod will make the force in case B bigger."

Neither student is correct. Discuss with your partners the errors made by each student. Write a correct description of how the forces compare in the space below. Explain.