JEE Main & Advanced Physics Electro Magnetic Induction JEE PYQ-Electro Magnetic Induction

  • question_answer
    A coil having n turns and resistance\[R\,\Omega \]. is connected with a galvanometer of resistance\[4R\,\Omega \]. This combination is moved in time t seconds from a magnetic field\[{{W}_{1}}\]weber to\[{{W}_{2}}\] weber. The induced current in the circuit is                                         [AIEEE 2004]

    A) \[\frac{{{W}_{2}}-{{W}_{1}}}{5Rnt}\]

    B) \[-\frac{n({{W}_{2}}-{{W}_{1}})}{5Rt}\]

    C) \[-\frac{({{W}_{2}}-{{W}_{1}})}{Rnt}\]  

    D) \[-\frac{n({{W}_{2}}-{{W}_{1}})}{Rt}\]

    Correct Answer: B

    Solution :

    [b] The rate of change of flux or emf induced in the coil is, \[e=-n\frac{d\phi }{dt}\]
    \[\therefore \]Induced current\[i=\frac{e}{R'}=-\frac{n}{R'}\frac{d\phi }{dt}\]
    Given,\[R'=R+4R=5R,d\phi ={{W}_{2}}-{{W}_{1}},dt=t.\]
    (here,\[{{W}_{1}}\]and\[{{W}_{2}}\]are flux associated with one turn)
    Putting the given values in Eq. (i), we get
    \[i=-\frac{n}{5R}\frac{({{W}_{2}}-{{W}_{1}})}{t}\]


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