Question

A positively charged rod touches the wire of the electroscope and the leaves move apart. Then a negatively charged rod is brought close (but not touching) to the electroscope and the leaves move towards each other. Why? Are the leaves charged?

Answer 1

An electroscope is a device that is used to determine the presence of electric charge by means of electrostatic attraction and repulsion. The electroscope initially was neutrally charged as soon as the positively charged rod touched it thus the leaves move apart so here I am considering the electroscope gets positively charged.

Now if you will bring a negatively charged rod close (but not touching) to positively charged electroscope, electron flow will take place thus the leaves will become less positively charged and therefore the leaves will move closer to one another. Now if we assume the charge on the negatively charged rod is much larger as compared to the positive charge on the electroscope and as we bring the negatively charged rod closer we will see the leaves will initially drop to each other and then sudden rise again as the leaves has become negatively charged and this happens because a large number of electrons being repelled from the top end of the electroscope.