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RAJASTHAN PMT Rajasthan - PMT Solved Paper-2011

  • question_answer
    A wire of length 1 m and cross-sectional area \[4\times {{10}^{-9}}{{m}^{2}}\] is made of a metal of resistivity \[6\times {{10}^{-8}}\Omega -m.\]The  potential  difference needed to pass a current of 2 A in the wire is

    A)  75 V                                     

    B)  50 V

    C)  30 V                     

    D)         10 V

    Correct Answer: C

    Solution :

    Given,\[i=2\,\,A,\,\,l=1\,\,m,\,\,A=4\times {{10}^{-9}}{{m}^{2}}\]and\[\rho =6\times {{10}^{-8}}\Omega \text{-}m\] We know that                 \[V=iR\]and\[R=\frac{\rho l}{A}\]                 \[V=i\times \frac{\rho l}{A}\]                 \[V=\frac{2\times 6\times {{10}^{-8}}\times 1}{4\times {{10}^{-9}}}\]                 \[V=30\,\,volt\]


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