Assertion: We can protect electrically sensitive instruments by keeping them inside a metallic box.
Reason: Conductors can maintain a uniform electric field inside them.

Options

A. If both assertion and reason are correct and reason is a correct explanation of the assertion .
B. If both assertion and reason are correct but reason is not the correct explanation of assertion
C. If assertion is correct but reason is incorrect
D. If assertion is incorrect but reason is correct.

Answer

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

**Assertion:** We can protect electrically sensitive instruments by keeping them inside a metallic box.

**Reason:** Conductors can maintain a uniform electric field inside them.

### Step-by-Step Solution:

1. **Understanding the Assertion:**
- Electrically sensitive instruments are devices that can be affected by external electric fields.
- By placing these instruments inside a metallic box, we can shield them from external electric fields.

2. **Behavior of Conductors in Electric Fields:**
- When a conductor is placed in an external electric field, charges within the conductor redistribute themselves.
- This redistribution creates an induced electric field that opposes the external field.

3. **Electric Field Inside a Conductor:**
- Inside a perfect conductor, the electric field is zero. This is due to the fact that the induced electric field cancels out any external electric field.
- Therefore, any electrically sensitive instrument placed inside a metallic box (a conductor) will not be affected by external electric fields.

4. **Analyzing the Reason:**
- The reason states that "Conductors can maintain a uniform electric field inside them."
- This statement is incorrect because, while conductors can maintain a zero electric field inside them, they do not maintain a uniform electric field; rather, the electric field is zero.

5. **Conclusion:**
- The assertion is correct: we can protect electrically sensitive instruments by placing them inside a metallic box.
- The reason is incorrect: conductors do not maintain a uniform electric field inside them; they maintain a zero electric field.

### Final Answer:
The assertion is correct, but the reason is incorrect. Therefore, the correct option is that the assertion is true, and the reason is false.

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