The magnetic flux $\phi_B(t)$ through a coil at a time $t$ is given by $\phi_B(t)=$ $\phi_0 \cos \omega t$, where $0 \leq \omega t \leq \pi$ and $\phi_0$ is a non-zero constant. At what time is the magnitude of the induced emf a maximum?

• A

  $0$
• Correct answer
  B

  $\frac{\pi}{2 \omega}$
• C

  $\frac{\pi}{\omega}$
• D

  $\frac{\pi}{4 \omega}$

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