Q. In the figure given the value of $X$ resistance will be, when the p.d. between $B$ and $D$ is zero
A) $4\ ohm$
B) $6\ ohm$
C) $8\ ohm$
D) $9\ ohm$
Explanation
(c) Potential difference between $B$ and $D$ is zero, it means Wheatstone bridge is in balanced condition
So $\frac{P}{Q} = \frac{R}{S} \Rightarrow \frac{21}{3 + \frac{8X}{(8 + X)}} = \frac{18}{6} \Rightarrow X = 8\Omega$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.