Torque = MBsinΦ
Torque will be maximum when Φ =90•
Torque maximum = MB.
Ans:A.

To understand why the maximum value of torque acting on a magnet when suspended in a uniform magnetic field of intensity B is MB, we need to consider the behavior of a magnetic dipole in a magnetic field.

1. Magnetic Moment:
The magnetic moment of a magnet is a measure of its ability to interact with a magnetic field. It is defined as the product of the strength of the magnet and the distance between the poles. Mathematically, magnetic moment (M) is given by M = m * l, where m is the strength of the magnet and l is the distance between the poles.

2. Torque on a Magnetic Dipole:
When a magnetic dipole is placed in a magnetic field, it experiences a torque. The torque (τ) acting on a magnetic dipole is given by τ = M x B, where M is the magnetic moment of the dipole and B is the magnetic field vector.

3. Maximum Torque:
The torque acting on a magnetic dipole is maximum when the dipole is aligned parallel or anti-parallel to the magnetic field. In this case, the angle between the magnetic moment vector and the magnetic field vector is either 0° or 180°. Let's consider the case when the angle is 0°.

- When the angle between M and B is 0°, the torque is given by τ = M * B * sin(0°) = 0.
- When the angle between M and B is 180°, the torque is given by τ = M * B * sin(180°) = 0.

4. Conclusion:
From the above analysis, we can see that the maximum torque acting on a magnetic dipole occurs when the angle between the magnetic moment vector and the magnetic field vector is 90°. In this case, the torque is given by τ = M * B * sin(90°) = M * B.

Therefore, the maximum value of torque acting on a magnet when suspended in a uniform magnetic field of intensity B is MB (option A).