Question

What is the torque exerted by a bar magnet on itself due to its field?

• A. maximum
• B. medium
• C. None of the above
• D. zero

Answer 1

Answer: (D)

zero

Answer 2

A bar magnet experiences torque only when placed in an external magnetic field. It cannot exert a net torque on itself due to its own internal magnetic field because internal forces and torques within a system always sum to zero. The torque on a magnetic dipole (like a bar magnet) is given by the cross product of its magnetic moment ($\vec{M}$) and the external magnetic field ($\vec{B}$), i.e., $\vec{\tau} = \vec{M} \times \vec{B}$.