J & K CET Engineering J and K - CET Engineering Solved Paper-2013

  • question_answer
    A long straight wire is carrying a current of\[12\text{ }A\]334. The magnetic field at a distance of \[8\text{ }cm\]is \[({{\mu }_{0}}=4\pi \times {{10}^{-7}}\,\,N/{{A}^{2}})\]

    A) \[2\times {{10}^{-4}}Wb/{{m}^{2}}\]   

    B)  \[3\times {{10}^{-5}}\text{ }Wb/{{m}^{2}}\]

    C)  \[4\times {{10}^{-4}}Wb/{{m}^{2}}\]   

    D)  \[4\times {{10}^{-5}}\text{ }Wb/{{m}^{2}}\]

    Correct Answer: B

    Solution :

    Magnetic field \[B=\frac{{{\mu }_{0}}I}{2\pi r}\] Given. \[\mu =4\pi \times {{10}^{-7}}N/{{A}^{2}},\] \[r=8cm=8\times {{10}^{-2}}m\] \[I=12\,\,A\] \[B=\frac{4\pi \times {{10}^{-7}}}{2\pi }\times \frac{12}{8\times {{10}^{-2}}}\] \[\Rightarrow \] \[B=3\times {{10}^{-5}}\,Wb/{{m}^{2}}\]


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