CMC Medical CMC-Medical VELLORE Solved Paper-2009

  • question_answer
    A closely wound flat circular coil of 25 turns of wire has diameter of 10 cm which carries current of 4 A, the flux density at the centre of a coil will be

    A)  \[2.28\times {{10}^{-6}}T\]        

    B)  \[1.679\times {{10}^{-6}}T\]

    C)  \[1.256\times {{10}^{-3}}T\]      

    D)  \[1.572\times {{10}^{-5}}T\]

    Correct Answer: C

    Solution :

                    Number of turns in the coil, n = 25 Diameter of coil, d = 10 cm      = 0.1 m \[\therefore \] Radius,    \[r=\frac{0.1}{2}=0.05\,m\] Current         \[i=4\,A\] Hence, flux density of the coil at the centre is given by \[B=\frac{{{\mu }_{0}}}{4\pi }\times \frac{2\pi ni}{r}\] \[={{10}^{-7}}\times \frac{2\pi \times 25\times 4}{0.05}\] \[=1.256\times {{10}^{-3}}T\] \[(\because {{\mu }_{0}}=4\pi \times {{10}^{-7}}N{{A}^{-1}}{{m}^{-1}})\]


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