Charge acquired by a glass rod when rubbed with silk:
When a glass rod is rubbed with silk, it acquires a positive charge. This process is known as charging by friction. The reason behind this phenomenon lies in the transfer of electrons between the two materials.

Explanation:
- When the glass rod is rubbed with silk, electrons from the glass rod are transferred to the silk.
- Glass is a good insulator, so it holds onto its positive charge, while silk being a good conductor allows the electrons to flow through it easily.
- This transfer of electrons leaves the glass rod with a deficiency of electrons, giving it a positive charge.
- The silk, on the other hand, gains extra electrons from the glass rod, acquiring a negative charge.

Key points:
- Rubbing the glass rod with silk causes a transfer of electrons.
- Glass rod gains a positive charge due to the loss of electrons.
- Silk gains a negative charge due to the gain of electrons.
- This process is known as charging by friction.
In conclusion, when a glass rod is rubbed with silk, the glass rod acquires a positive charge due to the transfer of electrons between the two materials. This phenomenon is a result of the difference in conductivity between the materials, with the glass holding onto its positive charge and the silk gaining a negative charge.

Positive charge