JCECE Engineering JCECE Engineering Solved Paper-2013

  • question_answer
    A coil is wound on a transformer of rectangular cross-section. If all the linear dimensions of the transformer are increased by a factor 2 and the number of turns per unit length of the coil remains the same, the self-inductance increases by a factor of

    A) \[4\]

    B) \[8\]

    C)  \[12\]

    D)  \[16\]

    Correct Answer: B

    Solution :

    We have, self-inductance,\[L=\frac{{{\mu }_{0}}{{n}^{2}}A}{l}\] Given, \[n/l\] is constant, doubling the length would double \[n\] also. Besides this, area would become four times on doubling linear dimensions. So,          \[\frac{{{L}_{2}}}{{{L}_{1}}}=\frac{n_{2}^{2}}{n_{1}^{2}}\cdot \frac{{{A}_{2}}}{{{A}_{1}}}\times \frac{{{l}_{1}}}{{{l}_{2}}}\] Here,     \[\frac{{{L}_{2}}}{{{L}_{1}}}=4\times 4\times \frac{1}{2}=8\] \[\Rightarrow \]               \[{{L}_{2}}=8{{L}_{1}}\]


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