A hemi-spherical network of radius `a` is made by using a conducting wire of resistance per unit length `r`. The equivalent resistance across `OP` is

Options

A. `(ra(pi+3))/(8)`
B. `(ra(pi+2))/(8)`
C. `(ra(pi+4))/(8)`
D. `(ra(pi+1))/(8)`

Explanation

Points `A`, `B`, `C` and `D` are at same potential therefore no current will be flowing through `AB`, `BC`, `CD` and `DA`
`:. R_(eq)=(R_(OA)+R_(AP))//4=(r//4)((pia)/(2)+a)`