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KVPY Sample Paper KVPY Stream-SX Model Paper-15

  • question_answer
    A copper wire is stretched to make it 0.5% longer. The percentage change in its electrical resistance if its volume remains unchanged is:

    A) 2.5%

    B) 0.5%

    C) 1.0%

    D) 2.0%

    Correct Answer: C

    Solution :

    \[R\,=\,\frac{\rho l}{A}\,and\,volume\,(V)\,=\,Al\] \[\text{R}\,=\,\frac{\rho {{l}^{2}}}{\text{V}}\] \[\Rightarrow \]   \[\frac{\Delta \text{R}}{\text{R}}\,=\,\frac{2\Delta l}{l}\,=\,1%\](V= constant)


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