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KVPY Sample Paper KVPY Stream-SX Model Paper-5

  • question_answer
    In the circuit shown the cell is ideal. The coil has an inductance of 4H and zero resistance. F is a fuse of zero resistance and will blow when the current through it reaches 5A. The switch is closed at t = 0. The fuse will blow-

    A) After 5 sec

    B) After 2 sec

    C) After 10 sec

    D) Just after closing of S

    Correct Answer: C

    Solution :

    [C]
    Applying Kirchoff voltage law \[E=L\frac{di}{dt}\]
    Where E=2V and L=4H
    \[di=\frac{E}{L}dt\]
    \[\int\limits_{0}^{i}{\,di=\int\limits_{0}^{t}{\frac{E}{L}dt}}\]
    \[i=\frac{E}{L}t\]
    \[i=\frac{2}{4}t=0.5t\]
    \[i=0.5\,\,t\]
    Fuse will blow when i become 5A
    So 5=0.5 t
    \[t=10\sec \]
    After 10 sec F will blow


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