Physics · Current Electricity

JEE Main 2024 — 1 February, Shift 2 — Question 46

In a metre-bridge when a resistance in the left gap is $2 \Omega$ and unknown resistance in the right gap, the balance length is found to be 40 cm . On shunting the unknown resistance with $2 \Omega$ , the balance length changes by :

Option A:
22.5 cm
Correct
Option B:
20 cm
Option C:
62.5 cm
Option D:
65 cm

Answer: A

Step-by-step solution

First case $\frac{2}{40}=\frac{\mathrm{X}}{60} \Rightarrow \mathrm{X}=3 \Omega$ In second case

$X^{\prime}=\frac{2 \times 3}{2+3}=1.2 \Omega$ $\frac{2}{\ell}=\frac{1.2}{100-\ell}$ $200-2 \ell=1.2 \ell$

$\ell=\frac{200}{3.2}=62.5 \mathrm{~cm}$ Balance length changes by 22.5 cm

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Exam: JEE Main 2024
Paper: 1 February, Shift 2
Subject: Physics
Chapter: Current Electricity
Topic: Electrical Measuring Instruments

Answer: A

Step-by-step solution

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