JEE Main & Advanced Physics Electrostatics & Capacitance JEE PYQ-Electrostatics and Capacitance

  • question_answer
    Figure shows a network of capacitors where the number indicates capacitances in micro Farad. The value of capacitance C if the equivalent capacitance between point A and B is to be \[1\mu F\] is: [JEE ONLINE 10-04-2016]

    A)             \[\frac{33}{23}\mu F\]

    B) \[\frac{31}{23}\mu F\]

    C)             \[\frac{32}{23}\mu F\]

    D) \[\frac{34}{23}\mu F\]

    Correct Answer: C

    Solution :

    [c] \[\frac{8\times 12}{8}=4\mu F\]
                \[4\mu F+4\mu F=8\mu E\]
                \[\frac{8\times 1}{8+1}=\frac{8}{9}\mu F\]
                \[\frac{8\times 1}{8+11}=\frac{32}{12}=\frac{8}{3}\mu F\]
                \[\frac{8}{3}+\frac{8}{9}=\frac{24+8}{9}=\frac{32}{9}\mu C\]
                \[\frac{\frac{32}{9}\times C}{\frac{32}{9}+C}=1\Rightarrow \frac{32}{9}\times C=\frac{32}{9}+C\]
                \[\Rightarrow C\left( \frac{32-9}{9} \right)=\frac{32}{9}\]
    \[C=\frac{32}{23}\mu F\]


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