JEE Main & Advanced Physics Magnetism Question Bank Self Evaluation Test - Magnetism and Matter

  • question_answer
    The earth?s magnetic field lines resemble that of a dipole at centre of the earth. If the magnetic moment of this dipole is close to\[8\times {{10}^{22}}A{{m}^{2}}\], the value of earth?s magnetic field near the equator is close to (radius of the earth \[=6.4\times {{10}^{6}}m\])

    A) 0.6 Gauss

    B) 1.2 Gauss

    C) 1.8 Gauss

    D) 0.32 Gauss

    Correct Answer: A

    Solution :

    [a] Given \[M=8\times {{10}^{22}}\,A{{m}^{2}}\] \[d={{R}_{e}}=6.4\times {{10}^{6}}m\] Earth's magnetic field, \[B=\frac{{{\mu }_{0}}}{4\pi }.\frac{2M}{{{d}^{3}}}\] \[=\frac{4\pi \times {{10}^{-7}}}{4\pi }\times \frac{2\times 8\times {{10}^{22}}}{{{(6.4\times {{10}^{6}})}^{3}}}\] \[\cong \,0.6\,Gauss\]


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