12th Class Physics Electrostatics & Capacitance Question Bank Case Based (MCQs) - Electric Potential and Capacitance

  • question_answer
    If a parallel plate air capacitor consists of two circular plates of diameter 8 cm. At what distance should the plates be held so as to have the same capacitance as that of sphere of diameter 20 cm ?

    A) 9 mm

    B) 4 mm

    C) 8 mm

    D) 2 mm

    Correct Answer: B

    Solution :

    As, \[\frac{{{\varepsilon }_{0}}A}{d}=4\pi {{\varepsilon }_{0}}R\] or \[\frac{{{\varepsilon }_{0}}\pi {{D}^{2}}}{4d}=4\pi {{\varepsilon }_{0}}R\] or \[d=\frac{{{D}^{2}}}{16R}=\frac{{{\left( 0\,.\,08 \right)}^{2}}}{16\times 0\,.\,10}\] \[=4\,\times {{10}^{-3}}\,m\,=\,4\,mm\]


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