A neutral ball is suspended by a string.

A positively charged insulating rod is placed
near the ball, which is observed to be attracted to the rod.
Why is this?
1. The ball becomes negatively charged by
induction.
2. The string is not a perfect conductor.
3. The number of electrons in the ball is
greater than in the rod.
4. The ball becomes positively charged by
induction.
5. There is a rearrangement of the electrons
in the ball.

There is a rearrangement of the electrons

in the ball. When induction starts to occur, the rearrangement of the electrons to get near the side of the ball which a positive charge is present creates a visible attraction between the two objects.

The correct explanation for why the neutral ball is attracted to the positively charged insulating rod is:

4. The ball becomes positively charged by induction.

When a positively charged object, such as the insulating rod, is brought near a neutral object, it causes a redistribution of the electrons within the neutral object. In this case, the presence of the positively charged rod causes the electrons in the neutral ball to move away from the rod and towards the opposite side of the ball. As a result, the side of the ball closer to the rod becomes positively charged, while the side farther from the rod becomes negatively charged. The positive charge on the closer side of the ball is attracted to the rod, causing the ball to be attracted towards it. Hence, the ball becomes positively charged by induction and is attracted to the positively charged insulating rod.

To determine why the neutral ball is attracted to the positively charged insulating rod, let's analyze the provided answer choices:

1. The ball becomes negatively charged by induction.
Induction is the process through which charges redistribute within an object without direct contact. In this scenario, the positively charged insulating rod induces a redistribution of the charge in the neutral ball, but it does not necessarily become negatively charged. Thus, this answer choice is not correct.

2. The string is not a perfect conductor.
The conductivity of the string is not relevant to the attraction between the ball and the charged rod. The string's properties do not influence the behavior of charges in this scenario. This answer choice is also incorrect.

3. The number of electrons in the ball is greater than in the rod.
The number of electrons in the ball compared to the rod is not a determining factor in the attraction between them. The attraction is due to charging effects, not the difference in the number of electrons. This answer choice is incorrect.

4. The ball becomes positively charged by induction.
This is the correct answer choice. The positively charged insulating rod induces a redistribution of charges in the neutral ball. Negative charges in the ball are attracted to the rod, causing the ball to become positively charged. Opposite charges attract each other, leading to the observed attraction between the ball and the rod.

5. There is a rearrangement of the electrons in the ball.
This answer choice is similar to option 4 in explaining the phenomenon. When the positively charged rod is brought near the neutral ball, there is a rearrangement of electrons within the ball. Electrons in the ball are attracted towards the rod, causing a net positive charge on the ball, leading to the observed attraction between the ball and the rod. Hence, this answer choice is also correct.

Therefore, the correct answer choices are 4. The ball becomes positively charged by induction and 5. There is a rearrangement of the electrons in the ball.