A thin wire of length ' $L$ ' made of an insulating material is bent to form a circular loop and a positive charge ' $\mathrm{q}$ ' is given so that it is distributed uniformly around the circumference of the loop. The loop is then rotated with an angular speed ' $\omega$ ' about an axis passing through its centre. If a uniform magnetic field B directed parallel to the plane of the loop is applied then the magnitude of the magnetic torque on the loop is

• Correct answer
  A

  $\frac{\mathrm{q} \omega \mathrm{L}^2 \mathrm{~B}}{8 \pi^2}$
• B

  $\frac{\mathrm{q} \omega \mathrm{L}^2 \mathrm{~B}}{4 \pi^2}$
• C

  $\frac{\mathrm{q} \omega \mathrm{L}^2 \mathrm{~B}}{2 \pi^2}$
• D

  $\frac{\mathrm{q} \omega \mathrm{L}^2 \mathrm{~B}}{\pi^2}$

Hence, the correct answer is option: 'A'.