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The figure below shows a highly negatively charged rod being brought slowly near the cap of a positively charged leaf electroscope. It is observed that the leaf initially falls and then rises. Explain this observation.

Answer Text:
The negative charge on the rod initially neutralize the positive charge on the leaf and the plate. As the rod is moved towards the cap, electrons are repelled to the leaf making it to fall. As the rod is brought nearer, the excess negative charge flows to the leaf and the plate where they repel each other making the leaf rise.