Punjab Medical Punjab - MET Solved Paper-2006

  • question_answer
    A wire is cut into four pieces, which are put together by sides to obtain one conductor. If the original resistance of wire was\[R\], the resistance of the bundle will be:

    A) \[\frac{R}{4}\]                                  

    B) \[\frac{R}{8}\]

    C) \[\frac{R}{16}\]                                

    D) \[\frac{R}{32}\]

    Correct Answer: C

    Solution :

    For a wire of length \[l\], area of cross-section\[A\], and specific resistance \[\rho \],  the resistance is given by                 \[R=\frac{\rho l}{A}\] From above equation it is clear that resistance is directly proportional to length. When wire is cut into 4 pieces then resistance of each part is                 \[R\,\,\propto \frac{1}{4}\]        \[\Rightarrow \]        \[R\,\,=\frac{R}{4}\] Also, equivalent resistance for parallel combination is                 \[\frac{1}{R}=\frac{1}{{{R}_{1}}}+\frac{1}{{{R}_{2}}}+\frac{1}{{{R}_{3}}}+\frac{1}{{{R}_{4}}}\]


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