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JEE Main & Advanced Physics Electro Magnetic Induction Question Bank Critical Thinking

  • question_answer
    As shown in the figure, P and Q are two coaxial conducting loops separated by some distance. When the switch S is closed, a clockwise current \[{{I}_{P}}\] flows in P (as seen by E) and an induced current \[{{I}_{{{Q}_{1}}}}\] flows in Q. The switch remains closed for a long time. When S is opened, a current \[{{I}_{{{Q}_{2}}}}\] flows in Q. Then the directions of \[{{I}_{{{Q}_{1}}}}\] and \[{{I}_{{{Q}_{2}}}}\] (as seen by E) are                     [IIT JEE (Screening) 2002]

    A)            Respectively clockwise and anticlockwise

    B)            Both clockwise

    C)            Both anticlockwise

    D)            Respectively anticlockwise and clockwise

    Correct Answer: D

    Solution :

               When switch S is closed magnetic field lines passing through Q increases in the direction from right to left. So, according to Lenz?s law induced current in Q i.e. \[{{I}_{{{Q}_{1}}}}\] will flow in such a direction so that the magnetic field lines due to \[{{I}_{{{Q}_{2}}}}\]passes from left to right through Q. This is possible when \[{{I}_{{{Q}_{1}}}}\] flows in anticlockwise direction as seen by E. Opposite is the case when switch S is opened i.e. \[{{I}_{{{Q}_{2}}}}\]will be clockwise as seen by E.


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