Question

Two unknown resistrance X and Y are connected to left and right gaps of a meter bridge and the balancing point is obtained at 80 cm from left. When a 10$\Omega$ resistance is connected in paralle to x, the balance point is 50 cm from left. The values of X and Y respectively are

• A. 40$\Omega$ , 9 $\Omega$
• B. 30$\Omega$ , 7.5$\Omega$
• C. 20$\Omega$ , 6$\Omega$
• D. 10$\Omega$ , 3$\Omega$

Answer 1

The correct option is B 30$\Omega$ , 7.5$\Omega$

Case 1

$\Rightarrow \frac{X}{Y}=\frac{80}{20}=4$

$X=4Y$

Case 2

$\frac{\frac{10X}{10+X}}{Y}=\frac{50}{50}=1$

$\Rightarrow \frac{10}{10+X}\times 4=1$

$10+X=40$

$X=30\Omega$

$Y=\frac{30}{4}=7.5\Omega$