BHU PMT BHU PMT (Screening) Solved Paper-2010

  • question_answer
    The capacitance of a parallel plate capacitor with air as medium is\[3\mu F\]. With the introduction of a dielectric medium between the plates, the capacitance becomes\[15\mu F\]. The permittivity of the medium is

    A)  \[5{{C}^{2}}{{N}^{-1}}{{m}^{-2}}\]

    B)  \[15{{C}^{2}}{{N}^{-1}}{{m}^{-2}}\]

    C)  \[0.44\times {{10}^{-10}}{{C}^{2}}{{N}^{-1}}{{m}^{-2}}\]

    D)  \[8.845\times {{10}^{-11}}{{C}^{2}}{{N}^{-1}}{{m}^{-2}}\]

    Correct Answer: C

    Solution :

                     Capacitance of a parallel plate capacitor with air is\[C=\frac{{{\varepsilon }_{0}}A}{d}\]d Capacitance of a same parallel plate capacitor with the introductory of a dielectric medium \[C'=\frac{k{{\varepsilon }_{0}}A}{d}\]where k is the dielectric constant of a medium. \[\therefore \]  \[\frac{C'}{C}=k\to =\frac{15}{3}=5\] and        \[k=\frac{\varepsilon }{{{\varepsilon }_{0}}}\]       or \[\varepsilon =k\,{{\varepsilon }_{0}}=5\times 8.854\times {{10}^{-12}}\]                 \[=0.4427\times {{10}^{-10}}{{C}^{2}}{{N}^{-1}}{{m}^{-2}}\]


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