Chhattisgarh PMT Chhattisgarh PMT Solved Paper-2006

  • question_answer
    There are 50 turns of a wire in every cm length of a long solenoid. If 4 A current is flowing in the solenoid, the approximate value of magnetic field along its axis at an internal point and at one end will be respectively

    A) \[\begin{align}   & 12.6\times {{10}^{-3}}\text{Wb/}{{\text{m}}^{\text{2}}} \\  & 6.3\times {{10}^{-3}}\text{Wb/}{{\text{m}}^{\text{2}}} \\ \end{align}\]                      

    B) \[\begin{align}   & 12.6\times {{10}^{-3}}\text{Wb/}{{\text{m}}^{\text{2}}} \\  & 25.1\times {{10}^{-3}}\text{Wb/}{{\text{m}}^{\text{2}}} \\ \end{align}\]

    C) \[\begin{align}   & 25.1\times {{10}^{-3}}\text{Wb/}{{\text{m}}^{\text{2}}} \\  & 12.6\times {{10}^{-3}}\text{Wb/}{{\text{m}}^{\text{2}}} \\ \end{align}\]     

    D) \[\begin{align}   & 25.1\times {{10}^{-5}}\text{Wb/}{{\text{m}}^{\text{2}}} \\  & 12.6\times {{10}^{-5}}\text{Wb/}{{\text{m}}^{\text{2}}} \\ \end{align}\]

    Correct Answer: C

    Solution :

    Given, \[N=50\text{ }turns/cm=5000\text{ }tums/m\] \[I=4A\] Magnetic field at an internal point \[={{\mu }_{0}}nI\]                 \[=4\pi \times {{10}^{-7}}\times 5000\times 4\]                 \[=8\pi \times {{10}^{-3}}\]                 \[=25.12\times {{10}^{-3}}Wb/{{m}^{2}}\] Magnetic field at one end \[=\frac{{{\mu }_{0}}nI}{2}\]                                                 \[=\frac{25.12\times {{10}^{-3}}}{2}\]                                                 \[=12.56\times {{10}^{-3}}Wb/{{m}^{2}}\]


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