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NEET Sample Paper NEET Sample Test Paper-89

  • question_answer
    A bar magnet of length 6 cm has a magnetic  moment of \[4\,J\,{{T}^{-1}}.\] Find the strength of magnetic field at a distance of 200 cm from the centre of the magnet along its equatorial line.

    A) \[4\times {{10}^{-8}}\] tesla

    B)        \[3.5\times {{10}^{-8}}\] tesla

    C) \[5\times {{10}^{-8}}\] tesla     

    D)        \[3\times {{10}^{-8}}\]tesla

    Correct Answer: C

    Solution :

    [c] Along the equatorial line, magnetic field strength \[B=\frac{{{\mu }_{0}}}{4\pi }\frac{M}{\left( {{r}^{2}}+{{\ell }^{2{{\,}^{3/2}}}} \right)}\] Given: \[M=4J{{T}^{-1}}\] r = 200cm = 2m \[\ell =\frac{6cm}{2}=3\,\,cm=3\times {{10}^{-2}}m\] \[\therefore \]\[B=\frac{4\pi \times {{10}^{-7}}}{4\pi }\times \frac{4}{{{\left[ {{2}^{2}}+{{\left( 3\times {{10}^{-2}} \right)}^{2}} \right]}^{3/2}}}\] Solving we get, B \[=5\times {{10}^{-8}}tesla\]


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