Manipal Engineering Manipal Engineering Solved Paper-2008

  • question_answer
    Two capacitors of capacitance C are connected in series. If one of them is filled with dielectric substance K, what is the effective capacitance?

    A) \[\frac{KC}{(1+K)}\]       

    B)         C (K + 1)

    C)  \[\frac{2KC}{K+1}\]                       

    D)         None of these

    Correct Answer: A

    Solution :

    When plates of capacitor are separated by a dielectric medium of dielectric constant\[K\], its                                   \[{{C}_{m}}=\frac{K{{\varepsilon }_{0}}A}{d}=K{{C}_{0}}\] \[ie,\]    \[{{C}_{m}}=K{{C}_{0}}\] Here,     \[{{C}_{0}}=C\] \[\therefore \]  \[{{C}_{m}}=KC\] Now, two capacitors of capacities\[KC\]and\[C\]are in series, their effective capacitance                 \[\frac{1}{C}=\frac{1}{KC}+\frac{1}{C}\] or            \[\frac{1}{C}=\frac{1+K}{KC}\] \[\therefore \]  \[C=\frac{KC}{K+1}\]


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