A: A magnetic dipole experiences maximum torque when it is placed normal to the magnetic field.
R: The minimum potential energy of magnetic dipole is zero.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion then mark (1)
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark 2.
C. If assertion is true statement but Reason is false, then mark (3)
D. If both Assertion and Reason are false statements, then mark (4)

Answer

To solve the assertion and reason question, we will analyze both statements step by step.

### Step 1: Analyze the Assertion
The assertion states: "A magnetic dipole experiences maximum torque when it is placed normal to the magnetic field."

- The torque (\( \tau \)) experienced by a magnetic dipole in a magnetic field is given by the formula:
\[ \tau = \mathbf{m} \times \mathbf{B} = mB \sin \theta \]
where:
- \( \mathbf{m} \) is the magnetic dipole moment,
- \( \mathbf{B} \) is the magnetic field,
- \( \theta \) is the angle between \( \mathbf{m} \) and \( \mathbf{B} \).

- For torque to be maximum, \( \sin \theta \) must be maximum, which occurs when \( \theta = 90^\circ \). At this angle, the magnetic dipole is placed normal (perpendicular) to the magnetic field.

**Conclusion for Assertion**: The assertion is true.

### Step 2: Analyze the Reason
The reason states: "The minimum potential energy of a magnetic dipole is zero."

- The potential energy (\( U \)) of a magnetic dipole in a magnetic field is given by the formula:
\[ U = -\mathbf{m} \cdot \mathbf{B} = -mB \cos \theta \]

- To find the minimum potential energy, we need to analyze the cosine function:
- When \( \theta = 0^\circ \) (dipole aligned with the field), \( U = -mB \).
- When \( \theta = 90^\circ \) (dipole normal to the field), \( U = 0 \).
- When \( \theta = 180^\circ \) (dipole anti-aligned with the field), \( U = mB \).

- The minimum potential energy occurs when \( \theta = 0^\circ \) and is equal to \( -mB \), which is not zero.

**Conclusion for Reason**: The reason is false.

### Final Conclusion
- The assertion is true, and the reason is false. Therefore, the correct answer is that the assertion is true, but the reason is false.