question_answer

Each branch in the following circuit has a resistance R. The equivalent resistance of the circuit between the points A and B is,

A)  R                                           

B)  2 R

C)  4 R                                        

D)  8 R

Correct Answer: B

Solution :

Due to symmetry about line AB network can be represented as Equivalent resistance \[=2R\] \[\frac{1}{V}+\frac{1}{-20}=\frac{-1}{15}\] \[\frac{1}{V}=\frac{1}{20}-\frac{1}{15}\]\[\frac{1}{V}=\frac{3-4}{5\times 12}=-\frac{1}{60}\]