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JEE Main & Advanced JEE Main Paper (Held On 26 May 2012)

  • question_answer
    The electrical resistance R of a conductor of length \[l\] and area of cross section a is given by\[R=\frac{\rho l}{a}\]where \['\rho '\]is the electrical resistivity. What is the dimensional formula for electrical conductivity' \['\sigma '\]which is reciprocal of resistivity?   JEE Main Online Paper (Held On 26-May-2012)  

    A) \[[{{M}^{-1}}{{L}^{-3}}{{T}^{3}}{{A}^{2}}]\]         

    B)                        \[[M{{L}^{-3}}{{T}^{-3}}{{A}^{2}}]\]

    C)                        \[[M{{L}^{-3}}{{T}^{-3}}{{A}^{-2}}]\]       

    D)                        \[[{{M}^{-2}}{{L}^{3}}{{T}^{2}}{{A}^{-1}}]\]

    Correct Answer: A

    Solution :

                    Dimensional formula for electrical resistivity,\[\rho =[M{{L}^{3}}{{T}^{-3}}{{A}^{-2}}]\] Dimensional formula for electrical conductivity, \[\sigma =\frac{1}{\rho }\] is \[[{{M}^{-1}}{{L}^{-3}}{{T}^{3}}{{A}^{2}}]\]


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