A current carrying loop in a uniform magnetic field will experience

Options

A. force only
B. torque only
C. both torque and force
D. neither torque nor force

Answer

To solve the question regarding the behavior of a current-carrying loop in a uniform magnetic field, we will analyze the forces and torques acting on the loop.

### Step-by-Step Solution:

1. **Understanding the Setup**:
- Consider a current-carrying loop placed in a uniform magnetic field. The current flows through the loop, and the magnetic field is uniform across the area of the loop.

2. **Force on a Current-Carrying Wire**:
- The force \( \mathbf{F} \) on a segment of wire carrying current \( I \) in a magnetic field \( \mathbf{B} \) is given by the equation:
\[ \mathbf{F} = I \mathbf{L} \times \mathbf{B} \]
- Here, \( \mathbf{L} \) is the length vector of the wire segment in the direction of the current.

3. **Analyzing the Loop**:
- For a closed loop, if we consider the forces acting on opposite sides of the loop, they will be equal in magnitude but opposite in direction. This is because the segments of the loop are parallel and carry the same current.

4. **Net Force Calculation**:
- Since the forces on opposite sides of the loop cancel each other out, the net force \( \mathbf{F}_{\text{net}} \) acting on the entire loop is:
\[ \mathbf{F}_{\text{net}} = 0 \]

5. **Torque on the Loop**:
- Although the net force is zero, the loop can still experience torque. The torque \( \tau \) on a current loop in a magnetic field is given by:
\[ \tau = \mathbf{m} \times \mathbf{B} \]
- Where \( \mathbf{m} \) is the magnetic moment of the loop, defined as:
\[ \mathbf{m} = I \cdot A \cdot \hat{n} \]
- Here, \( A \) is the area of the loop and \( \hat{n} \) is the unit vector normal to the plane of the loop.

6. **Conclusion**:
- The net force on the current-carrying loop in a uniform magnetic field is zero, but the torque is non-zero. This means the loop will not translate but may rotate depending on the orientation of the magnetic field relative to the plane of the loop.

### Final Answer:
A current-carrying loop in a uniform magnetic field will experience **zero net force** and **non-zero torque**.