When a coil carrying current is set with its plane perpendicular to the direction of magnetic field, then torque on the coil is……………. .

Answer

To determine the torque on a coil carrying current when it is positioned with its plane perpendicular to the direction of the magnetic field, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Torque Formula**:
The torque (\(\tau\)) on a coil in a magnetic field is given by the equation:
\[ \tau = \mathbf{M} \times \mathbf{B} \]
where \(\mathbf{M}\) is the magnetic moment of the coil and \(\mathbf{B}\) is the magnetic field.

2. **Define the Magnetic Moment**:
The magnetic moment (\(\mathbf{M}\)) of a coil can be expressed as:
\[ \mathbf{M} = N \cdot I \cdot \mathbf{A} \]
where \(N\) is the number of turns in the coil, \(I\) is the current flowing through the coil, and \(\mathbf{A}\) is the area vector of the coil.

3. **Determine the Orientation**:
When the plane of the coil is perpendicular to the magnetic field, the area vector (\(\mathbf{A}\)) is aligned with the magnetic field (\(\mathbf{B}\)). This means the angle (\(\theta\)) between \(\mathbf{A}\) and \(\mathbf{B}\) is 0 degrees.

4. **Calculate the Torque**:
The torque can also be expressed in terms of the angle between the magnetic moment and the magnetic field:
\[ \tau = N \cdot I \cdot A \cdot B \cdot \sin(\theta) \]
Since \(\theta = 0\) degrees, we have:
\[ \sin(0) = 0 \]
Therefore, substituting this into the torque equation gives:
\[ \tau = N \cdot I \cdot A \cdot B \cdot 0 = 0 \]

5. **Conclusion**:
The torque on the coil when its plane is perpendicular to the direction of the magnetic field is:
\[ \tau = 0 \]

### Final Answer:
The torque on the coil is zero.