JEE Main & Advanced Sample Paper JEE Main Sample Paper-2

  • question_answer
    Two circular coils P and Q lie in the same plane co-axially. The coil P has 10 turns and radius 4 cm and carries current of 1 A. The coil Q has 40 turns of radius 4 cm and current in it is such that resultant magnetic field at the common centre becomes zero. When coil P is rotated such that planes of coils become perpendicular to each other, then magnetic field at the common centre becomes

    A) \[15.7\times {{10}^{-7}}Wb/{{m}^{2}}\]

    B) \[22.2\times {{10}^{-7}}Wb/{{m}^{2}}\]

    C)  \[12.6\times {{10}^{-7}}Wb/{{m}^{2}}\]               

    D)  \[18.9\times {{10}^{-7}}Wb/{{m}^{2}}\]

    Correct Answer: B

    Solution :

    The magnetic field at centre of coil P becomes \[{{B}_{1}}=\frac{{{\mu }_{0}}{{i}_{1}}{{N}_{1}}}{2r}=\frac{{{\mu }_{0}}\times 1\times 10}{2\times 4}=\frac{4\pi \times {{10}^{-7}}\times 10}{8}\]             \[=5\pi \times {{10}^{-7}}\] Also,      \[{{B}_{2}}={{B}_{1}}=5\pi \times {{10}^{-7}}\] \[\therefore \]  \[B=\sqrt{B_{1}^{2}+B_{2}^{2}}=5\sqrt{2}\pi \times {{10}^{-7}}Wb/{{m}^{2}}\]


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