# Charged Balls

There is a ball (A) is carrying a uniformly distributed unknown charge(wich may be zero) and an uncharged copper ball (D). A positive test charge (T) experiences highly attraction with ball (A) and (D). What is the nature of the force between balls A and D if they are brought very close together?

Choices are

attractive
repulsive
no force

What I think the answer should be is repulsive because since (T) is strongly attacted to both balls, that means both balls must have a same charge; therefore repel when brought close together.

However it says in the problem that the copper ball (D) is uncharged. What does that mean? It has equal amount of electrons and protons?

Also what does copper come to play here? I know it is an extremely good conductor of electricity but does this fact play an important role in this question?

Tide
Homework Helper
You know what sign the charge is on A. Since D is uncharged but nevertheless attracted to the test charge you must infer that the test charge induces charge on D. It is reasonable to conclude that were the test charge negative you would get the same result.

What would you then conclude about A interacting with D?

Then I would believe that both A and D are negatively charged and when placed near eachother they will repel?

Tide
Homework Helper
D is not charged!

A positive test charge (T) experiences highly attraction with ball (A) and (D).
Meaning D is negative?!??

vanesch
Staff Emeritus