JEE Main & Advanced Sample Paper JEE Main Sample Paper-17

  • question_answer
    In the figure, a capacitor is filled with  dielectrics. The resultant capacitance is

    A) \[\frac{2{{\varepsilon }_{0}}A}{d}\left[ \frac{1}{{{k}_{1}}}+\frac{1}{{{k}_{2}}}+\frac{1}{{{k}_{3}}} \right]\]

    B)  \[\frac{{{\varepsilon }_{0}}A}{d}\left[ \frac{1}{{{k}_{1}}}+\frac{1}{{{k}_{2}}}+\frac{1}{{{k}_{3}}} \right]\]

    C)  \[\frac{2{{\varepsilon }_{0}}A}{d}\left[ {{k}_{1}}+{{k}_{2}}+{{k}_{3}} \right]\]

    D)  None of these

    Correct Answer: D

    Solution :

     \[{{C}_{1}}=\frac{{{K}_{1}}{{\varepsilon }_{0}}\frac{A}{2}}{\left( \frac{d}{2} \right)}=\frac{{{K}_{1}}{{\varepsilon }_{0}}A}{d};\] \[{{C}_{2}}=\frac{{{K}_{2}}{{\varepsilon }_{0}}\left( \frac{A}{2} \right)}{\left( \frac{d}{2} \right)}=\frac{{{K}_{2}}{{\varepsilon }_{0}}A}{d}\]and  \[{{C}_{3}}=\frac{{{K}_{3}}{{\varepsilon }_{0}}A}{2d}\] Now, \[{{C}_{eq}}={{C}_{3}}+\frac{{{C}_{1}}{{C}_{2}}}{{{C}_{1}}+{{C}_{2}}}\]                 \[=\left( \frac{{{K}_{3}}}{2}+\frac{{{K}_{1}}{{K}_{2}}}{{{K}_{1}}+{{K}_{2}}} \right).\frac{{{\varepsilon }_{0}}A}{d}\]


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