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

  • question_answer
    A 10 cm long bar magnet of magnetic moment \[1.34\,A{{m}^{2}}\] is placed in the magnetic meridian with its south pole pointing geographical south. The neutral point is obtained at a distance of 15 cm from the centre of the magnet. Calculate the horizontal component of earth's magnetic field.

    A) \[0.12\times {{10}^{-4}}\,T\]    

    B)        \[0.21\times {{10}^{-4}}T\]

    C) \[0.34\times {{10}^{-4}}T\]      

    D) \[0.87\times {{10}^{-7}}T\]

    Correct Answer: C

    Solution :

    [c] \[B=\frac{{{\mu }_{0}}}{4\pi }\frac{M}{{{({{r}^{2}}+{{\ell }^{2}})}^{3/2}}}={{B}_{H}}\] Given that \[{{\mu }_{0}}=4\pi \times {{10}^{-7}}\,T\,m{{A}^{-1}}\] \[M=1.34\,A{{m}^{2}}\] \[r=15\,cm=0.15\,m\] and \[\ell =5.0\,cm=0.05\,m\] \[\therefore \,\,\,\,\,{{B}_{H}}={{10}^{-7}}\times \frac{1.34}{{{[{{(0.15)}^{2}}+{{(0.5)}^{2}}]}^{3/2}}}\] \[={{10}^{-7}}\times \frac{1.34}{0.025\sqrt{0.025}}=0.34\times {{10}^{-4}}\,T\]


You need to login to perform this action.
You will be redirected in 3 sec spinner