JEE Main & Advanced Physics Magnetic Effects of Current / करंट का चुंबकीय प्रभाव JEE PYQ-Magnetic Effects Of Current

  • question_answer
    A long solenoid has 200 turns/cm and carries a current j. The magnetic field at its centre is 6.28 \[\times {{10}^{-2}}Wb/{{m}^{2}}\]. Another long solenoid has 100 turns/cm and it carries a current\[i/3\]. The value of the magnetic field at its centre is                                        [AIEEE 2006]

    A)       \[1.05\times {{10}^{-2}}Wb/{{m}^{2}}\]           

    B) \[1.05\times {{10}^{-5}}Wb/{{m}^{2}}\]

    C) \[1.05\times {{10}^{-3}}Wb/{{m}^{2}}\]

    D) \[1.05\times {{10}^{-4}}Wb/{{m}^{2}}\]

    Correct Answer: A

    Solution :

    [a] Magnetic field due to a long solenoid is given by
    \[B={{\mu }_{0}}ni\]
    From given data,
    \[6.28\times {{10}^{-2}}={{\mu }_{0}}\times 200\times {{10}^{2}}\times i\]            ...(i)
    (for 1st solenoid)
    and       \[B={{\mu }_{0}}\times 100\times {{10}^{2}}\times (i/3)\]       ...(ii)
    (for IInd solenoid)
    Solving Eqs. (i) and (ii). we get
    \[B\approx 1.05\times {{10}^{-2}}\,Wb/{{m}^{2}}\]


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