Two spherical conductors A and B of radii a and b (`b gt a`) are placed concentrically in air. A is given charged +Q while B is earthed. Then the equivalent capacitance of the system is

Options

A. `4piin_(0) (r_(1).r_(2))/(r_(2)-r_(1))`
B. `4piin_(0) (r_(1)+r_(2))`
C. `4piin_(0) .r_(2)`
D. `4piin_(0) (r_(2)^2)/(r_(2)-r_(1))`

Answer

A