12th Class Physics Electrostatics & Capacitance Question Bank MCQ - Electrostatic Potential and Capacitance

  • question_answer
    Effective capacitance between A and B in the figure shows below is: \[\left( {{C}_{1}}={{C}_{2}}=20\mu F,\,{{C}_{3}}={{C}_{4}}=10\,\mu F \right)\]

    A) \[10\,\mu F\]

    B) \[15\,\mu F\]

    C) \[20\,\mu F\]                 

    D) \[25\,\mu F\]

    Correct Answer: B

    Solution :

    (b) \[15\,\mu F\] Here, \[{{C}_{1}}\] and \[{{C}_{2}}\] are in series, hence their capacitance is given by             \[\frac{1}{C'}=\frac{1}{{{C}_{1}}}+\frac{1}{{{C}_{2}}}\]             \[\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{1}{C'}=\frac{1}{20}+\frac{1}{20}\]             \[\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,C'=10\,\mu F\]             Similarly,       \[\frac{1}{C''}=\frac{1}{{{C}_{3}}}+\frac{1}{{{C}_{4}}}\]             \[\Rightarrow \,\frac{1}{C''}=\frac{1}{10}+\frac{1}{10}\,\,\Rightarrow C''=5\mu F\] Now, C and C" are in parallel. Hence, resultant capacitance C will be \[C=C'+C''=10+5+15\mu F\]


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