Predict what would happen if you touched the knob of a positively charged electroscope with a negatively charged object. Explain your prediction.

Electrons would flow from negatively charged object to the positively charged electroscope and the leaves of the electroscope would come back to their original position or come back closer together.

Explanation:

A positively charged electeoscope has positive charges on its leaves, thereby causing the leaves to repel each other (like charges repel).

But touching this electroscope with a negatively charged body will lead to a rush of electrons from the negatively charged body into the electroscope through its knob, to the stem and subsequently to the leaves. This incoming electrons causes the charges on the leaves of the electroscope to become a little bit more balanced, so the repulsion that made the them far apart goes away and the leaves of the electroscope come back closer together.