VMMC VMMC Medical Solved Paper-2009

  • question_answer
    The earth has volume V and surface area A, then capacitance would be

    A)                       \[4\pi {{\varepsilon }_{0}}\frac{A}{V}\] 

    B)                                        \[4\pi {{\varepsilon }_{0}}\frac{V}{A}\]                 

    C)                        \[12\pi {{\varepsilon }_{0}}\frac{V}{A}\]                               

    D)                        \[12\pi {{\varepsilon }_{0}}\frac{A}{V}\]

    Correct Answer: C

    Solution :

    Volume of sphere (earth) \[=\frac{4}{3}\pi {{R}^{3}}\] Where R is the radius of the sphere. Area of the sphere \[=4\pi {{R}^{2}}\] Now, \[\frac{V}{A}=\frac{R}{3}\]                                                              ?(i) Capacitance of a sphere \[C=4\pi {{\varepsilon }_{0}}R\]               ...(ii) From Eqs. (i) and (ii), we get \[C=4\pi {{\varepsilon }_{0}}\left( \frac{3V}{A} \right)=\frac{12\pi {{\varepsilon }_{0}}V}{A}\]


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