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RAJASTHAN ­ PET Rajasthan PET Solved Paper-2006

  • question_answer
    Two wires of same metal have the same length but their cross-section are in the ratio 3:1. They are joined in series. The resistance of the thicker wire is 10\[\Omega \]. The total resistance of the combination will be

    A)  \[40\,\Omega \]

    B)  \[\frac{40}{3}\Omega \]

    C)  \[\frac{5}{2}\,\Omega \]

    D)  \[100\,\Omega \]

    Correct Answer: A

    Solution :

     For same material and same length \[\frac{{{R}_{2}}}{{{R}_{1}}}=\frac{{{A}_{1}}}{{{A}_{2}}}=\frac{3}{2}\] \[\Rightarrow \] \[{{R}_{2}}=3{{R}_{1}}\] Resistance of thick wire \[{{R}_{1}}=10\,\Omega \] \[\therefore \]Resistance of then wire \[{{R}_{2}}=30\,\Omega \] Total resistance in series \[=10+30=40\,\Omega \]


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