Assertion: A metal object kept in timevarying magnetic field gets cooled.
Reason: When metal object is kept inside time-varying magnetic field then due to electromagnetic induction electric current start flowing on the surface.

Options

A. If both assertion and reason are correct and reason is correct explanation of the assertion
B. If both assertion and reason are correct but reason is not correct explanation of the 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 both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understand the Assertion**: The assertion states that a metal object kept in a time-varying magnetic field gets cooled.
- **Analysis**: When a metal object is placed in a time-varying magnetic field, it does not necessarily cool down. In fact, it may heat up due to the induced currents flowing through it.

2. **Understand the Reason**: The reason states that when a metal object is kept inside a time-varying magnetic field, electric current starts flowing on the surface due to electromagnetic induction.
- **Analysis**: This statement is correct. According to Faraday's law of electromagnetic induction, a changing magnetic field induces an electromotive force (EMF) in the conductor, leading to the flow of electric current.

3. **Evaluate the Relationship**: Now, we need to determine if the reason correctly explains the assertion.
- The reason correctly describes what happens when a metal object is placed in a time-varying magnetic field (current flows due to induction). However, it does not explain why the assertion (the object cools) is true. In fact, the assertion is false.

4. **Conclusion**: Based on the analysis:
- The assertion is incorrect (the metal object does not cool down).
- The reason is correct (current flows due to electromagnetic induction).
- Therefore, the correct option is D: the assertion is incorrect, and the reason is correct.

### Final Answer:
The correct option is D: Assertion is incorrect, Reason is correct.