When a positively charged rod is brought nearer the cap of a positively charged electroscope, the leaves divergence will?

Analyze the question: A gold-leaf electroscope is already positively charged, so its leaves diverge. A positively charged rod is brought near the cap (without touching). What happens to the leaves?

Concept: Charging by induction

• Like charges repel and unlike charges attract.
• When a charged body is brought near the cap, the free electrons in the electroscope's metal are attracted or repelled, which redistributes the charge.

Step-by-step solution:

1. The electroscope is positively charged, so the cap, rod and leaves carry an excess of positive charge. The leaves repel each other and diverge.
2. A positive rod is brought near the cap. It attracts the free electrons in the metal toward the cap.
3. Electrons move up from the stem and leaves to the cap. The cap becomes more negative locally, and the leaves lose electrons.
4. The leaves therefore become even more positive, since they have fewer electrons than before.
5. More positive charge on both leaves means stronger repulsion, so the divergence increases.

Result: The leaves diverge further. Among the options, C (diverge) best matches this, meaning the divergence increases.

Why not the others?

• A (be induced): charge is induced, but this does not describe the leaves' behaviour.
• B (converge): this happens if a negative rod is brought near a positively charged electroscope, because electrons are pushed down to the leaves and neutralise some of their charge.
• D (remain constant): the leaves would change, not stay the same.

Tip: Remember the rule "same sign as the electroscope → divergence increases; opposite sign → divergence decreases (leaves collapse)." This is also how you test the sign of an unknown charge: an increase in divergence confirms the charge on the rod is the same as that on the electroscope.