Question

Watch the diagram carefully and answer the following questions: -
a) The pith ball was initially at position A.
When a glass rod after rubbing with silk is
brought near it moves to B. State the reason.​

Answer 1

A pith ball is a very small, lightweight object that picks up electric charge quite well. A charged pith ball works well to show the Coulomb force between two charged objects. If a glass rod is rubbed with silk, the silk rubs some electrons off the rod. The rod thus becomes positively charged.

Touching the positively-charged rod to two pith ball gives the balls each a small positive charge. Since like charges repel, the pith balls repel one another.

If an ebonite rod is rubbed with fur, the rod rubs some electrons off the fur. The rod thus becomes negatively charged and attracts the positively-charged pith balls.