A long solenoid of radius $0.01 \mathrm{m}$ has $600$ turns per metre. A smaller coil of $100$ turns is wrapped closely around the centre of the bigger solenoid. If the current in the solenoid rises from zero to $2 \mathrm{A}$ in $1 \mathrm{ms}$, find the emf induced in the smaller coil.

An aeroplane, the distance between the edges of its wings being 30 m, is landing down with a velocity of 300 km h-1. If, while landing, the wings of the aeroplane be east-west, find out the potential difference between the edges of the wings be north-south, then? (Given : ${\mathrm{B}}_{\mathrm{H}}=0.4\times {10}^{-4}\mathrm{T}$).