Charging an insulator problem

[fwFAWFSERG]

1. i have the answer, but just don't understnad it
A small metal ball is given a negative charge, then brought near (i.e., within a few millimeters) to end A of the rod. What happens to end A of the rod when the ball approaches it closely this first time?

Select the expected behavior.

X strongly repelled
X strongly attracted
weakly attracted
X weakly repelled
X neither attracted nor repelled

The Attempt at a Solution

Well, i first figured that the negatively charged ball and the side A of the rod would weakly repel, seeing that there are two negative charges, and one postive charge, a ratio of 2:3 negative.
-that answer was wrong
then i thought that since it was an insulator, and is not even really charged (having a nuetral charge as a whole) it would be neither attracted nor repelled.
-also wrong.
-so, an insulator does not transfer charge well, but i don't see how this helps me answer the question really.

so it's weakly attracted because the insulator rearranges to give a small dipole moment, which makes it weakly attracted?

 

[Carid]

Right. The negative charge on the ball will attract the positive charges on the rod and repel the negative charges.

The image of the rod is to show you that there is no overall charge on the rod.

Have you had any lab practice using gold leaf electroscopes? Very instructive!

 

[thomate1]

As a scientist, it is important to approach problems with a logical and evidence-based mindset. In this situation, we have a negatively charged metal ball and an insulator rod. It is known that like charges repel and opposite charges attract. However, in the case of an insulator, the charges are not able to move freely and redistribute themselves like in a conductor.

When the negatively charged ball is brought near the rod, it will induce a slight polarization in the insulator. This means that the negative charges in the insulator will slightly move away from the negatively charged ball, creating a small dipole moment. This dipole moment will then be weakly attracted to the negatively charged ball.

Therefore, the expected behavior is for the end A of the rod to be weakly attracted to the negatively charged ball. It is important to note that this attraction will be weaker compared to if the rod was a conductor, due to the insulator's limited ability to redistribute its charges. This can explain why the original answers of strongly attracted or weakly repelled were incorrect.

In conclusion, the answer to the problem is weakly attracted, due to the polarization and resulting dipole moment in the insulator. It is important to always consider the properties and behavior of materials when approaching scientific problems.