Question

A gold leaf electroscope is given a positive charge so that its leaves diverge. How is the divergence of leaves affected, when a glass rod rubbed with silk is rolled on the disc of electroscope?

• A. divergence increases
• B. divergence decreases
• C. divergence remains same
• D. can't say

Answer 1

Answer: (B)

divergence decreases

On rubbing a glass rod with silk, the electrons from the glass rod get transferred to the silk. The silk now has an excess of electrons and so is negatively-charged. On the other hand, the glass rod is deficient in electrons and hence is positively-charged.
In the above case, the silk undergoes negative electrification.
When the positively charged glass rod is touched on the disc of a negatively charged gold leaf electroscope, the divergence between the gold leaves decreases as unlike charges attract each other.
Hence, the divergence decreases as the glass rod rubbed with silk is rolled on the disc of electroscope.