Question

Consider three plastic balls (A, B, and C), each carrying a uniformly distributed charge equal to either +Q, -Q or zero, and an uncharged copper ball (D). A positive test charge (T) experiences the forces shown in the figure when brought very near to the individual balls. The test charge T is strongly attracted to A, strongly repelled from B, weakly attracted to C, and strongly attracted to D.

Assume throughout this problem that the balls are brought very close together. What is the nature of the force between balls A and C?

(A) strongly attractive
(B) strongly repulsive
(C) weakly attractive
(D) neither attractive nor repulsive

Answer 1

The force between balls A and C is weakly attractive because A has a negative charge and the properties of ball C suggest it is uncharged or has a very small negative charge.

Step-by-step explanation:

To determine the nature of the force between balls A and C, we must first understand the charges they carry. Since ball A strongly attracts the positive test charge T, we can infer that ball A has a negative charge. Ball C weakly attracts the test charge, which suggests that ball C has either a zero charge or a very small negative charge. According to Coulomb's law, unlike charges attract and like charges repel. Therefore, if ball C is uncharged or has a very small negative charge, it will be weakly attracted to ball A, which carries a negative charge.

Given that ball A has a negative charge and ball C is weakly attractive to the positive test charge, we can conclude that the force between balls A and C would be option (C) weakly attractive.

Answer 2

(C) weakly attractive

Step-by-step explanation:

Since the positive test charge T is strongly attracted to A, the net charge of A must be negative. C is made of plastic, this is an insulator material, this means that it can be polarized. Since the test charge T is weakly attracted to C, the charge on C must be zero. Therefore C can be polarized by the presence of an electric field such as that generated by A, so this will generate a weak electrical attraction between A and C.