Assertion : The magnetic flux through a closed surface containing a bar magnet is zero.
Reason : Gauss's law applies in the case of electric flux only.

Options

A. A
B. B
C. C
D. D

Explanation

To solve the given question, we will analyze both the assertion and the reason provided.

### Step 1: Analyze the Assertion
The assertion states that "The magnetic flux through a closed surface containing a bar magnet is zero."

- When a bar magnet is placed inside a closed surface, the magnetic field lines emerge from the north pole and enter the south pole.
- For every magnetic field line that exits the closed surface from the north pole, there is a corresponding line that enters the surface at the south pole.
- Therefore, the total magnetic flux through the closed surface is indeed zero because the number of lines entering equals the number of lines exiting.

**Conclusion for Step 1:** The assertion is **true**.

### Step 2: Analyze the Reason
The reason states that "Gauss's law applies in the case of electric flux only."

- Gauss's law is a fundamental principle in electromagnetism that applies to both electric and magnetic fields.
- For electric fields, Gauss's law states that the electric flux through a closed surface is proportional to the charge enclosed within that surface.
- Similarly, Gauss's law for magnetism states that the magnetic flux through a closed surface is zero, which aligns with our assertion regarding the bar magnet.

**Conclusion for Step 2:** The reason is **false**.

### Final Conclusion
- The assertion is true, while the reason is false. Therefore, the correct answer to the question is that the assertion is correct, but the reason is incorrect.