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JEE Main & Advanced Physics Magnetism JEE PYQ-Magnetism

  • question_answer
    The coercivity of a small magnet where the Ferro magnet gets demagnetized is \[3\times {{10}^{3}}A\,{{m}^{-1}}.\]The current required to be passed in a solenoid of length 10 cm and number of turns 100, so that the magnet gets demagnetized when inside the solenoid, is:                       [JEE MAIN 2014]

    A) 3 A

    B) 6 A

    C) 30 mA

    D) 60 mA

    Correct Answer: A

    Solution :

    [a] \[B={{\mu }_{0}}H\]
    \[{{\mu }_{0}}ni={{\mu }_{0}}H\]
    \[i=\frac{H}{n}=\frac{3\times {{10}^{3}}}{1000}=3A\]


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