When the glass rod is rubbed with the piece of silk, then according to known tradition :

Options

A. Both get negatively charged
B. Both get positively charged
C. Glass rod got negatively charged and silk piece got positively charged
D. Glass rod got positively charged and silk piece got negatively charged

Explanation

**Step-by-Step Solution:**

1. **Understanding the Materials**:
- We have a glass rod and a piece of silk cloth.

2. **Rubbing the Materials**:
- When the glass rod is rubbed with the silk cloth, friction occurs between the two materials.

3. **Static Electricity Phenomenon**:
- This rubbing generates static electricity. Static electricity is the result of an imbalance of electric charges within or on the surface of a material.

4. **Charge Transfer**:
- During the rubbing process, electrons are transferred from one material to another.

5. **Identifying Charge Types**:
- In this case, the glass rod loses electrons and becomes positively charged.
- The silk cloth gains those electrons and becomes negatively charged.

6. **Conclusion**:
- Therefore, after rubbing the glass rod with silk, the glass rod is positively charged, and the silk cloth is negatively charged.

**Final Answer**: The glass rod becomes positively charged, and the silk piece becomes negatively charged.

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