BCECE Engineering BCECE Engineering Solved Paper-2014

  • question_answer
    The specific resistance of a wire is \[\rho \], its volume is 3m3 and its resistance is \[3\Omega \], then its length will be

    A) \[\frac{3}{\sqrt{\rho }}\]                                              

    B) \[\frac{\sqrt{3}}{\rho }\]

    C) \[\frac{5}{\sqrt{\rho }}\]                                              

    D) \[\frac{\sqrt{5}}{\rho }\]

    Correct Answer: A

    Solution :

    \[\text{Volume =Area  }\!\!\times\!\!\text{  length}\] \[3=Al\] \[A=\frac{3}{l}\] Resistance \[R=\rho \frac{l}{A}\] \[3=\frac{\rho l}{\left( \frac{3}{l} \right)}=\frac{\rho {{l}^{2}}}{3}\] \[{{l}^{2}}=\frac{9}{\rho }\] \[\Rightarrow \]               \[l=\frac{3}{\sqrt{\rho }}\]


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