JEE Main & Advanced Physics Magnetism JEE PYQ-Magnetism

  • question_answer
    The magnetic field of earth at the equator is approximately \[4\times {{10}^{-5}}T.\]The radius of earth is \[6.4\times {{10}^{6}}m.\] Then the dipolemoment of the earth will be nearly of the order of:                           [JEE ONLINE 09-04-2014]

    A) \[{{10}^{23}}A{{m}^{2}}\]

    B) \[{{10}^{20}}A{{m}^{2}}\]

    C) \[{{10}^{16}}A{{m}^{2}}\]

    D) \[{{10}^{10}}A{{m}^{2}}\]

    Correct Answer: A

    Solution :

    Given, \[B=4\times {{10}^{-5}}T\]
    \[{{R}_{E}}=6.4\times {{10}^{6}}m\]
    Dipole moment of the earth M = ?
    \[B=\frac{{{\mu }_{0}}}{4\pi }\frac{M}{{{d}^{3}}}\]
    \[4\times {{10}^{-5}}=\frac{4\pi \times {{10}^{-7}}\times M}{4\pi \times {{\left( 6.4\times {{10}^{6}} \right)}^{3}}}\]
    \[\therefore \]\[M\cong {{10}^{23}}A{{m}^{2}}\]


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