NEET Sample Paper NEET Sample Test Paper-23

  • question_answer
    A long straight wire carrying a current of 30 A is placed in an external uniform magnetic field of induction \[4\times {{10}^{-4}}T.\] The magnetic field is acting parallel to the direction of current. The magnitude of the resultant magnetic induction in tesla at a point 2.0 cm  away from the wire is:\[({{\mu }_{0}}=4\pi \times {{10}^{-7}}H/m)\]

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

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

    C) \[5\times {{10}^{-4}}\]                   

    D) \[6\times {{10}^{-4}}\]   

    Correct Answer: C

    Solution :

    Magnetic field at a point 2.0 cm from the straight conductor carrying current of 3QA is \[B=\frac{{{\mu }_{0}}i}{2\pi R}=\frac{4\pi \times {{10}^{-7}}\times 30}{2\pi \times 2\times {{10}^{-2}}}=3\times {{10}^{-4}}T\] The conductor is placed in the external field \[{{\vec{B}}_{0}}\]which is directed perpendicular to\[\vec{B}.\]. Therefore, the resultant magnetic field is \[{{B}_{r}}=\sqrt{{{B}^{2}}+B_{0}^{2}}+\sqrt{{{3}^{2}}+{{4}^{2}}}\times {{10}^{-4}}T\] \[=5\times {{10}^{-4}}T\] Hence, the correction option is [c].


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