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VIT Engineering VIT Engineering Solved Paper-2008

  • question_answer
    Three solenoid coils of same dimension, same number of turns and same number of layers of winding are taken. Coil 1 with inductance \[{{L}_{1}}\] was wound using a Mn wire of resistance 11\[\Omega /m;\]Coil 3 with inductance \[{{L}_{3}}\] was wound using the similar wire but the direction of winding was reversed in each layer; Coil 3 with inductance \[{{L}_{3}}\] was wound using a superconducting wire. The self-inductance of the coils \[{{L}_{1}}\], \[{{L}_{2}}\], \[{{L}_{3}}\] are

    A)  \[{{L}_{1}}={{L}_{2}}={{L}_{3}}\]

    B)  \[{{L}_{1}}={{L}_{2}};{{L}_{3}}=0\]

    C)  \[{{L}_{1}}={{L}^{3}};{{L}^{2}}=0~\]

    D)  \[{{L}_{1}}>{{L}_{2}}>{{L}_{3}}\]  

    Correct Answer: C

    Solution :

    As inductance \[{{L}_{2}}\] was wound using the similar wire but the direction of winding is reversed, so flux through \[{{L}_{2}}\] is zero. \[\therefore \] \[{{L}_{2}}\propto \,\phi =0\] Also, \[{{L}_{1}}={{L}_{3}}\] Therefore, \[{{L}_{1}}={{L}_{3}},\,{{L}_{2}}=0\]


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