A network of twelve resistances each of resistance `R` form a square of square as shown in the figure. The outer square is fitted in in a metal ring of negligible resistance. Find the resistance between centre of the square and the ring.

Options

A. `R//4`
B. `R//2`
C. `3R//9`
D. `R//12`

Answer

C

Explanation

(c ) `1,2,3,4` are at same potential , `5, 6, 7, 8` are at same potential
`R_(eq) = (R )/(4) + (R )/(8) = (3 R)/(8)`