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Consider the diagram below depicting an electroscope (a), a charged rod (b), and a conducting wire connected to ground (c). Notice that the foil leaves inside the electroscope are able to move. The steps are numbered for the action of bringing the rod close to the electroscope and the attachment/detachment to/from ground.

Created for Albert.io. Copyright 2016. All rights reserved.

Which of the following is the best explanation for why the leaves stay spread apart in image 4 and not resting vertically as in image 1?

A

Negative particles were driven down the grounding wire by the negative rod leaving the electroscope with a net positive charge. When both the rod and the grounding wire were moved away from the electroscope, the negative particles were unable to return to the electroscope leaving the net positive charge as evidenced by the repulsion in the foil leaves.

B

Positive particles were drawn up the grounding wire by the negative rod leaving the electroscope with a net positive charge. When both the rod and the grounding wire were moved away from the electroscope, the positive particles were unable to return to ground leaving the net positive charge on the electroscope as evidenced by the repulsion in the foil leaves.

C

The negatively charged rod transferred some of its negative charge onto the electroscope. When both the rod and the grounding wire were moved away from the electroscope, the excess negative charge transferred from the rod was unable to escape the electroscope, leaving a net charge on the electroscope as evidenced by the repulsion in the foil leaves.

D

When the negative rod was brought near the electroscope, it pushed negative particles from the top of the electroscope down to the foil leaves as shown in image 2. The grounding wire drew enough positive charges up from ground to neutralize the top of the electroscope and redistribute the negative charges that were in the foil leaves as shown in image 3. When both rod and grounding wire were removed, the excess positive charges redistributed themselves causing the foil to repel due to a net positive charge.

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