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Current Electricity

JEE Main level, numerical answer, medium

289 of 380

Question 289 of 380

Resistance are connected in a meter bridge circuit as shown in the figure. The balancing length ${l}_{1}$ is $40cm$ . Now an unknown resistance $x$ is connected in series with $P$ and new balancing length is found to be $80cm$ measured from the same end. Then the value of $x$ will be _____ $\Omega$ .

Show answer and solution

Answer: 20

Applying balanced condition for meter bridge
Initially,

\dfrac{P}{Q}=\dfrac{40cm}{60cm}=\dfrac{2}{3}...\left(1\right)

Finally,

\dfrac{P+x}{Q}=\dfrac{80cm}{20cm}=\dfrac{4}{1}...\left(2\right)

Dividing equation

\left(2\right)

by (

\left(1\right)

\dfrac{P+x}{P}=4\times \dfrac{3}{2}=6

\Rightarrow 1+\dfrac{x}{P}=6\Rightarrow \dfrac{x}{P}=5

∴x=5P=5\times 4=20\Omega

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JEE Main 2025 Apr 2 Shift 1 question paper

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