• # question_answer 17) Electron beam is allowed to pass normally through mutually perpendicular magnetic electric fields. If magnetic field induction and electric field strength are $0.0004\text{ }Wb/{{m}^{2}}$ and $3000\text{ }V/m$ respectively and beam suffers no deflection. Then the velocity of electron will be: A) $1.2\times {{10}^{6}}\text{ }m/s$B)  $7.5\times {{10}^{12}}\text{ }m/s$C)  $7.5\times {{10}^{6}}\text{ }m/s$       D)  none of these

Here, magnetic field $B=0.0004\text{ }Wb/{{m}^{2}}.$ Electric field       $E=3000\text{ }V/m.$ The velocity of an electron, when beam suffers no deflection is given by                         $V=\frac{E}{B}$                                 $=\frac{3000}{0.0004}=7.5\times {{10}^{6}}\,m/s$