question_answer

All wires have same resistance and equivalent resistance between A and B is Ry. Now keys are closed, then the equivalent resistance will become

A) \[\frac{7{{R}_{0}}}{3}\]

B) \[\frac{7{{R}_{0}}}{9}\]

C) \[7{{R}_{0}}\]

D) \[\frac{{{R}_{0}}}{3}\]

Correct Answer: B

Solution :

[b] If each resistor is r, then \[{{R}_{0}}=3r\text{ or }r=\frac{{{R}_{0}}}{3}\] When keys are closed, then