Which of the following cannot be charged easily by friction?

Options

A. A plastic scale
B. A copper rod
C. An inflated balloon
D. A woollen cloth

Explanation

To solve the question "Which of the following cannot be charged easily by friction?" we need to analyze the materials provided: a plastic scale, a copper rod, an inflated balloon, and a woolen cloth.

### Step-by-Step Solution:

1. **Identify the Materials**:
- Plastic scale
- Copper rod
- Inflated balloon
- Woolen cloth

2. **Classify the Materials**:
- **Non-conductors (Insulators)**: Plastic scale, inflated balloon, woolen cloth.
- **Conductors**: Copper rod.

3. **Understand Charging by Friction**:
- Non-conductors can be easily charged by friction because they do not allow the free movement of electrons.
- Conductors, on the other hand, allow electrons to move freely, making it difficult to maintain a charge when rubbed.

4. **Analyze Each Material**:
- **Plastic Scale**: Non-conductor, can be easily charged by friction.
- **Copper Rod**: Conductor, cannot be easily charged by friction.
- **Inflated Balloon**: Non-conductor, can be easily charged by friction.
- **Woolen Cloth**: Non-conductor, can be easily charged by friction.

5. **Conclusion**:
- The material that cannot be charged easily by friction is the **copper rod** because it is a conductor.

### Final Answer:
The correct answer is **copper rod**.

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