Question

The magnetic flux linked with the coil varies with time as $\phi = 3t^2+4t+9$.The magnitude of the induced emf of $2s$ is

• A. 9 V
• B. 16 V
• C. 3 V
• D. 4 V

Answer 1

Answer: (B)

16 V

Answer 2

As emf, $e=\frac{d \phi}{\text { dt }}\left(\frac{d \phi}{d t}\right.$. Aate of charge of magnetic flux) $=\frac{d}{d t}\left(3 t^{2}+4 t+9\right)$ $=6 t+4+0$ So, at $t =2 s,$ $e=6 \times 2+4=16\, V$