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