Chapter 6, Problem 17STP

To determine

To describe: the movement of rubber rod as the piece of silk is brought close to it.

Explanation of Solution

On rubbing the rubber rod on hair, the rubber is charged by contact. As the rubber rod turns into negatively charged, that means the hair becomes positively charged.

Similarly, the glass rod gets charged when it is rubbed with a piece of silk. However, here it is piece of silk that becomes negatively charged because the rod is said to have become positively charged.

The negatively charged rubber rod is suspended to rotate freely. When the negatively charged piece of silk is brought close to the negatively charged rubber rod, like charges opposes each other. Therefore, the rubber rod repels the piece of silk.

Conclusion: The rubber rod moves away from the piece of silk, as both are negatively charged and like charges repel each other.