A 30 cm long solenoid has 10 turns per cm and area of 5 cm^2. The current through the solenoid coil varies from 2 A to 4 A in 3.14 s. The e.m.f.…

A $\displaystyle 30$ cm long solenoid has $\displaystyle 10$ turns per cm and area of $\displaystyle 5 \mathrm{~cm}^2$. The current through the solenoid coil varies from $\displaystyle 2$ A to $\displaystyle 4$ A in $\displaystyle 3.14$ s. The e.m.f. induced in the coil is $\displaystyle \alpha \times 10^{-5} \mathrm{~V}$. The value $\displaystyle \alpha$ is $\displaystyle \_\_\_\_$.