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

  • question_answer
    A bar magnet has a length 8 cm. The magnetic field at a point at a distance 3 cm from the centre in the broad side-on position is found to be\[4\times {{10}^{-6}}T\]. The pole strength of the magnet is.

    A) \[6\times {{10}^{-5}}Am\]

    B) \[5\times {{10}^{-5}}Am\]

    C) \[2\times {{10}^{-4}}Am\]

    D) \[3\times {{10}^{-4}}Am\]

    Correct Answer: A

    Solution :

    [a] Magnetic field due to a bar magnet in the broad-side on position is given by \[B=\frac{{{\mu }_{0}}}{4\pi }\frac{M}{\left[ {{r}^{2}}+\frac{{{\ell }^{2}}}{4} \right]};M=m\ell \]. After substituting the values and simplifying we get \[B=6\times {{10}^{-5}}\,A-m\]


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