A U-shaped conducting wire of mass m=10 g , having length of its...

A U-shaped conducting wire of mass $m=10 g$, having length of its horizontal section as $\ell=20 \mathrm{~cm}$, is free to move vertically up and down. The two ends of the wire are immersed in mercury for proper electrical contact. The wire is in a homogeneous field of magnetic induction $B=0.1 T$ as shown. The wire jumps up to a height $h=3 m$ when a charge q , in the form of a current pulse, is sent through the wire. Considering that the duration of the current pulse is very small compared to the time of flight, the charge $q$ passed through the wire is estimated to be nearly