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JEE Main & Advanced JEE Main Paper (Held On 25 April 2013)

  • question_answer
                     The earth?s magnetic filed lines resemble of a dipole at the centre of the earth. It the magnetic moment of this dipole is close to\[8\times {{10}^{22}}\]\[\text{A}{{\text{m}}^{\text{2}}}\], the value of earth?s magnetic filed near the equator is close to (radius of earth =\[\text{6}\text{.4}\times \text{1}{{\text{0}}^{\text{6}}}\operatorname{m}\])     JEE Main Online Paper ( Held On 25  April 2013 )

    A)                 0.6 Gauss                            

    B)                                        1.2 Gauss

    C)                                        1.8 Gauss                            

    D)                                        032 Gauss

    Correct Answer: A

    Solution :

                    Given \[M=8\times {{10}^{22}}A{{m}^{2}}\] \[d={{\operatorname{R}}_{e}}=6.4\times {{10}^{6}}m\] 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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