`vecF` is the force on the arm of a square toop suspended in a uniform mdgnetic field. Net : force on remaining arnis is :

Options

A. `- vecF`
B. `vecF`
C. `-3 vecF`
D. `3 vecF`

Explanation

To solve the problem, we need to analyze the forces acting on the arms of a square loop suspended in a uniform magnetic field.

### Step-by-Step Solution:

1. **Understanding the Setup**:
- We have a square loop suspended in a uniform magnetic field.
- The loop carries a current, which interacts with the magnetic field to produce forces on the arms of the loop.

2. **Identifying the Forces**:
- The magnetic force on a current-carrying conductor in a magnetic field is given by the formula:
\[ \vec{F} = I (\vec{L} \times \vec{B}) \]
where \(I\) is the current, \(\vec{L}\) is the length vector of the conductor, and \(\vec{B}\) is the magnetic field.

3. **Analyzing the Arms Parallel to the Field**:
- For the two arms of the loop that are parallel to the magnetic field, the angle between the current direction and the magnetic field is 0 degrees.
- Therefore, the force on these arms is:
\[ \vec{F}_{\text{parallel}} = I (\vec{L} \times \vec{B}) = 0 \]
This is because the cross product of two parallel vectors is zero.

4. **Analyzing the Remaining Arms**:
- The other two arms of the square loop are perpendicular to the magnetic field.
- The force on these arms can be calculated using the same formula. Since the angle is 90 degrees, the force will be:
\[ \vec{F}_{\text{perpendicular}} = I L B \]
- If we denote the force on one of these arms as \(\vec{F}\), then the force on the other arm will be equal in magnitude but opposite in direction.

5. **Net Force on the Remaining Arms**:
- The total force on the two arms that are perpendicular to the magnetic field will be:
\[ \vec{F}_{\text{net}} = \vec{F} + (-\vec{F}) = 0 \]
- However, since we are interested in the net force on the remaining arms, we can express it as:
\[ \text{Net force on remaining arms} = -\vec{F} \]

6. **Conclusion**:
- The net force on the remaining arms of the square loop is given by:
\[ \text{Net force on remaining arms} = -\vec{F} \]

### Final Answer:
The net force on the remaining arms is \(-\vec{F}\).