KVPY Sample Paper KVPY Stream-SX Model Paper-5

  • question_answer
    A wire PQRS carrying a current I run along three edges of a cube of side \[\ell \] as shown. There exists a uniform magnetic field of magnitude B along one of the sides of the cube. The magnitude of the force acting on the wire is ?

    A) Zero                             

    B) \[I\ell B\]

    C) \[\sqrt{2}\,I\ell B\]          

    D) \[2\ell B\]

    Correct Answer: C

    Solution :

    [C] \[{{F}_{PQ}}=0\Rightarrow {{F}_{QR}}=I\ell B\] \[{{F}_{RS}}=I\ell B\] \[{{F}_{QR}}\] & \[{{F}_{RS}}\] are perpendicular to each other \[\therefore {{F}_{net}}=\sqrt{{{(I\ell B)}^{2}}+{{(I\ell B)}^{2}}}=\sqrt{2}I\ell B\]      

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