The radius of the circular plates of a parallel plate condenser is `'r'`. Air is there as the dielectric. The distance between the plates if its capacitance is equal to that of an isolated sphere of radius `r'` is.

Options

A. `(r^(2))/(4r')`
B. `(r^(2))/(r')`
C. `(r )/(r')`
D. `(r^(2))/(4)`

Answer

A

Explanation

`(in_(0) (pi r^(2)))/(d) = 4pi in_(0)r^(1) "" :. d = (r^(2))/(4r^(1))`