Question

Four resistance P, Q, R, X formed a Wheatstone bridge. The bridge is balanced when R=100$\Omega$. If P and Q are interchanged the bridge balances for R = 121$\Omega$. The value of X is

• A. 100$\Omega$
• B. 200$\Omega$
• C. 300$\Omega$
• D. 110$\Omega$

Answer 1

Answer: (D)

110$\Omega$

Case 1:

$\frac{P}{Q}=\frac{R}{X}$

$\frac{P}{Q}=\frac{100}{X}$ ---- 1

Case 2:

$\frac{Q}{P}=\frac{121}{X}$ ---- 2

$\Rightarrow \frac{X}{121}=\frac{100}{X}$

$X^2=100\times 121$

$\Rightarrow X=110\Omega$