question_answer

In the figure given the value of \[X\] resistance will be, when the p.d. between B and D is zero                  [MP PET 1993]

A)                    4 ohm

B)            6 ohm

C)                    8 ohm                              

D)            9 ohm

Correct Answer: C

Solution :

             Potential difference between B and D is zero, it means Wheatstone bridge is in balanced condition So \[\frac{P}{Q}=\frac{R}{S}\] Þ \[\frac{21}{3+\frac{8X}{(8+X)}}=\frac{18}{6}\]Þ \[X=8\Omega \]