Question

In a meter bridge experiment, null point is obtained at 40cm from left end when unknown resistance is inserted in left gap and a resistance of 60 $\Omega$ is inserted in the right gap. If resistance of 60$\Omega$ is kept same, but the wire in left gap is cut in two equal parts, and joined in parallel across the left gap, the new null point is at

• A. 40 cm from left end
• B. 20 cm from left end
• C. 10 cm from left end
• D. 100/7 cm from left end

Answer 1

Answer: (D)

100/7 cm from left end

$\frac{x}{60}=\frac{40cm}{100}-40cm$ $\Rightarrow x=40\Omega$

$\frac{10}{60}=\frac{I}{100}-I$

$I=\frac{100}{7}cm$