JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2009

  • question_answer
        A copper wire of cross-sectional area \[=2.0\text{ }m{{m}^{2}},\]resistivity\[=1.7\times {{10}^{-8}}\Omega m,\]carries a current of 1 A. The electric field in the copper wire is

    A)  \[8.5\times {{10}^{-5}}V{{m}^{-1}}\]     

    B)  \[8.5\times {{10}^{-4}}V{{m}^{-1}}\]

    C)  \[8.5\times {{10}^{-3}}V{{m}^{-1}}\]     

    D)  \[8.5\times {{10}^{-2}}V{{m}^{-1}}\]

    Correct Answer: C

    Solution :

                    From symmetry considerations and also from theory \[\frac{{{V}_{a}}}{{{V}_{d}}}=\frac{{{V}_{b}}}{{{V}_{c}}}\] \[E=\frac{V}{l}=\frac{IR}{l}=\frac{I\rho l}{Al}=\frac{I\rho }{A}\] \[=\frac{1\times 1.7\times {{10}^{-8}}}{2\times {{10}^{-6}}}\] \[=8.5\times {{10}^{-3}}V{{m}^{-1}}\]


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