Question

When a plastic rod rubbed with wool is brought near the knob of a negatively charged gold-leaf electroscope, the gold leaves:

• A. Dilate
• B. Contract
• C. Start oscilating
• D. Collapse completely

Answer 1

The correct option is A

Dilate

Charging by rubbed with wool

1. When a plastic rod is rubbed with wool, the negatively charged free electrons move from the wool to the plastic rod.
2. Thus static electricity is generated between the two particles.
3. As a result, the plastic rod becomes negatively charged.
4. When this negatively charged plastic rod is brought closer to the gold-leaf electroscope, the leaves start repelling due to the same charge.

As the leaves repel, they are spread out and start dilating.

Hence, option (A) is correct.