Assertion : The net magnetic force on a current loop in a uniform magnetic field is zero but torque may or may not be zero.
Reason : Torque on a current carrying coil in a magnetic field is given by `vec(tau)=nI(vec(A) X vec(B))`.

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

Answer

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

### Step 1: Understand the Assertion
The assertion states that "The net magnetic force on a current loop in a uniform magnetic field is zero but torque may or may not be zero."

- In a uniform magnetic field, the forces acting on opposite sides of the current loop cancel each other out, resulting in a net magnetic force of zero.
- However, the torque depends on the orientation of the loop with respect to the magnetic field. If the loop is aligned such that the angle between the area vector and the magnetic field vector is not 0° or 180°, the torque will be non-zero.

### Step 2: Understand the Reason
The reason states that "Torque on a current carrying coil in a magnetic field is given by \( \vec{\tau} = nI(\vec{A} \times \vec{B}) \)."

- This formula is indeed correct. Here, \( n \) is the number of turns in the coil, \( I \) is the current, \( \vec{A} \) is the area vector of the coil, and \( \vec{B} \) is the magnetic field vector.
- The torque can be expressed as \( \tau = nIA \sin \theta \), where \( \theta \) is the angle between the area vector and the magnetic field vector. The torque is zero when \( \theta \) is 0° or 180°.

### Step 3: Conclusion
- Both the assertion and the reason are true statements. However, the reason does not correctly explain the assertion because the assertion is about the net force being zero while the reason discusses torque.

### Final Answer
- The assertion is true, and the reason is also true, but the reason is not the correct explanation of the assertion.