1. When a glass rod is rubbed with silk piece, the free electrons in the glass rod are transferred to silk piece.
2. It is because the free electrons in the glass rod are tightly bound as compared to that in silk piece.
3. Since the glass rod looses electrons, it has a deficiency of electrons and hence acquires positive charge.
4. But, silk piece has excess of electrons.
5. So, it becomes negatively charged.
