question_answer

A circuit consists of five identical conductors as shown in figure. The two similar conductors are added as indicated by dotted lines. The ratio of resistances before and after addition will be

A)  \[\frac{7}{5}\]                                  

B)  \[\frac{3}{5}\]

C)  \[\frac{5}{3}\]                  

D)         \[\frac{6}{5}\]

Correct Answer: C

Solution :

After adjoining two conductors, the circuit will acquire the form shown in the following figure. From symmetry considerations, we conclude that the central conductor will not be effective in electric charge transfer. Therefore, if the initial resistance \[{{R}_{1}}\] of circuit was \[5\Omega \], where resistance of each conductor is \[1\Omega \], the new- resistance of the circuit will become