question_answer

Two spherical conductors \[{{A}_{1}}\] and \[{{A}_{2}}\] of radii \[{{r}_{1}}\]and \[{{r}_{2}}\left( {{r}_{2}}>{{r}_{1}} \right)\] are placed concentrically in air.  \[{{A}_{1}}\]is given a charge +Q while \[{{A}_{2}}\] is earthed. Then the equivalent capacitance of the system is

A) \[\frac{4\pi {{\in }_{0}}{{r}_{1}}{{r}_{2}}}{{{r}_{2}}-{{r}_{1}}}\]

B) \[4\pi r{{\in }_{0}}\left( {{r}_{1}}+{{r}_{2}} \right)\]

C) \[4\pi {{\in }_{0}}{{r}_{2}}\]

D) \[4\pi {{\in }_{0}}{{r}_{1}}\]