12th Class Physics Magnetism Question Bank MCQ - Moving Charges and Magnetism

  • question_answer
    A long straight wire in the horizontal plane carries a current of 75 A in north to south direction, magnitude and direction of field B at a point 3 m east of the wire is:

    A) \[4\times {{10}^{-6}}T\], vertical up

    B)   \[5\times {{10}^{-6}}T\], vertical down       

    C) \[5\times {{10}^{-6}}T\], vertical up

    D)   \[4\times {{10}^{-6}}T\], vertical down       

    Correct Answer: C

    Solution :

    (c) \[5\times {{10}^{-6}}T\], vertical up From Ampere circuital law                            \[\oint{\overrightarrow{B}\cdot \overrightarrow{dl}={{\mu }_{0}}{{l}_{enc}}}\] \[B\times 2\pi R={{\mu }_{0}}{{l}_{enc}}\] \[B=\frac{{{\mu }_{0}}{{l}_{enc}}}{2\pi R}=2\times {{10}^{-7}}\times \frac{75}{3}=5\times {{10}^{-6}}T\] The direction of field at the given point will be vertical up determined by the screw rule or right-hand rule.


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