A very small circular loop of radius $a$ is initially (at $t=0$ ) coplanar and concentric with a much larger fixed circular loop of radius b. A constant current $I$ flows in the larger loop. The smaller loop is rotated with a constant angular speed $\omega$ about the common diameter. The emf induced in the smaller loop as a function of time $t$ is

• A

  $\frac{\pi a^{2} \mu_{0} l}{2 b} \omega \cos (\omega t)$
• B

  $\frac{\operatorname{\pi a}^{2} \mu_{0}l}{2 b} \omega \sin \left(\omega^{2} t^{2}\right)$
• Correct answer
  C

  $\frac{\pi a^{2} \mu_{0} l}{2 b}$ $\omega sin$ $(\omega t)$
• D

  $\frac{\pi a^{2} \mu_{0}l}{2 b} \omega \sin ^{2}(\omega t)$

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