A $50 \mathrm{cm}$ long horizontal wire is falling down with a speed of $6 {\mathrm{ms}}^{-1}$ perpendicular to a uniform magnetic field of $1.1 \mathrm{Wb} {\mathrm{m}}^{-2}$. The magnetic field is directed from east to west. Calculate the emf induced in the wire. Which end of the wire (north or south) will be positive?

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 : ${\mathrm{B}}_{\mathrm{H}}=0.4\times {10}^{-4}\mathrm{T}$).