Question

In the figure given, the value of $X$ resistance when the potential differences between $B$ and $D$ is zero, is

• A. 4 ohm
• B. 6 ohm
• C. 8 ohm
• D. 9 ohm

Answer 1

Answer: (C)

Potential difference between $B$ and $D$ is zero, it means Wheatstone bridge is in balanced condition.

So $\frac{P}{Q}=\frac{R}{S}$
$\Rightarrow \frac{21}{3+\frac{8X}{(8+X)}}=\frac{18}{6}$
$\Rightarrow X=8\Omega$