Assertion : Earth's magnetic field does not affect the working of a moving coil galvanometer.
Reason: The earth's magnetic field is quite weak as compared to magnetic field produced in the moving coil galvanometer.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true and reason is not the correct explanation of assertion.
C. If assertion is ture but reason is false.
D. If both assertion and reason are false.

Explanation

To solve the question, we need to analyze both the assertion and the reason provided.

**Assertion:** Earth's magnetic field does not affect the working of a moving coil galvanometer.

**Reason:** The Earth's magnetic field is quite weak as compared to the magnetic field produced in the moving coil galvanometer.

### Step-by-Step Solution:

1. **Understanding the Assertion:**
- The assertion states that the Earth's magnetic field does not impact the functioning of a moving coil galvanometer. This implies that the galvanometer operates independently of the Earth's magnetic field.

2. **Understanding the Reason:**
- The reason given is that the Earth's magnetic field is weak compared to the magnetic field generated by the galvanometer itself. This suggests that the stronger magnetic field in the galvanometer is the primary factor influencing its operation.

3. **Evaluating the Assertion:**
- The assertion is true. The moving coil galvanometer is designed to function primarily based on the magnetic field created by its own field magnet, which is significantly stronger than the Earth's magnetic field.

4. **Evaluating the Reason:**
- The reason is also true. It accurately describes the relative strengths of the magnetic fields involved. The magnetic field produced by the galvanometer is indeed much stronger than the Earth's magnetic field.

5. **Determining the Relationship:**
- While both the assertion and the reason are true, the reason does not correctly explain the assertion. The assertion is true because the galvanometer's design allows it to operate effectively in its own magnetic field, regardless of the Earth's magnetic field. The reason merely states a fact about the strength of the fields but does not explain why the galvanometer is unaffected.

6. **Conclusion:**
- Therefore, the assertion is true, the reason is true, but the reason is not the correct explanation of the assertion.

### Final Answer:
- Assertion: True
- Reason: True
- Explanation: The reason does not adequately explain why the assertion is true.