A conducting circular loop is placed in a uniform magnetic field, $B=0.025 \mathrm{T}$ with its plane perpendicular to the loop. The radius of the loop is made to shrink at a constant rate of $1 \mathrm{mm} {\mathrm{s}}^{-1}$. The induced emf when the radius is $2 \mathrm{cm}$, is

• A

  $2\pi \mathrm{\mu V}$
• Correct answer
  B

  $\pi \mathrm{\mu V}$
• C

  $\frac{\mathrm{\pi }}{2}\mathrm{\mu V}$
• D

  $2 \mathrm{\mu V}$

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