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JEE Main & Advanced JEE Main Paper (Held on 09-4-2019 Afternoon)

  • question_answer
                A moving coil galvanometer has a coil with 175 turns and area \[1c{{m}^{2}}.\]It uses a torsion band of torsion constant \[{{10}^{-6}}\] N-m/rad. The coil is placed in a maganetic field B parallel to its plane. The coil deflects by\[1{}^\circ \]for a current of 1 mA. The value of B (in Tesla) is approximately :-             [JEE Main 9-4-2019 Afternoon]

    A) \[{{10}^{-3}}\]

    B) \[{{10}^{-1}}\]

    C) \[{{10}^{-4}}\]                    

    D) \[{{10}^{-2}}\]

    Correct Answer: A

    Solution :

    \[\tau =\vec{M}\times \vec{B}\]           \[C\theta =i\,NAB\]           \[{{10}^{-6}}\times \frac{\pi }{180}={{10}^{-3}}\times {{10}^{-4}}\times 175\times B\]           \[B={{10}^{-3}}\]Tesla,                


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