question_answer

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

A) R/4                  

B) R/2        

C) 3R/8     

D) R/12

Correct Answer: C

Solution :

[c] 1, 2, 3, 4 are at same potential; 5, 6, 7, 8 are at same potential.         \[{{R}_{eq}}=\frac{R}{4}+\frac{R}{8}=\frac{3R}{8}\]