• # question_answer A rigid conducting wire bent as shown, is released to fall freely in a horizontal magnetic field, which is perpendicular to the plane of the conductor. If magnetic field strength is B, then the emf induced across the points A and when it has fallen through a height h will be: A)  $B\ell \sqrt{2gh}$                 B) $B\ell \sqrt{gh}$C) $2B\ell \sqrt{gh}$                  D) $2B\ell \sqrt{2gh}$

The effective length is $AC={{l}_{0}}=\sqrt{{{\ell }^{2}}+{{\ell }^{2}}}=\sqrt{2}\ell$ Induced emf $=\varepsilon -B{{l}_{0}}v$ $=B\sqrt{2}\ell \sqrt{2gh}=2B\ell \sqrt{gh}$ $[\because \,v=\sqrt{2gh}]$ Hence, the correction option is [c].