A galvanmeter has a coil of resistance 200 Ω with a full scale deflection at 20 μ A . The value of resistance to be added to use it as an ammeter of range (0-20) mA is:

Physics · Current Electricity

JEE Main 2024 — 9 April, Shift 1 — Question 45

A galvanmeter has a coil of resistance $200 \Omega$ with a full scale deflection at $20 \mu \mathrm{~A}$ . The value of resistance to be added to use it as an ammeter of range $(0-20) \mathrm{mA}$ is:

Option A:
$0.40 \Omega$
Option B:
$0.20 \Omega$
Correct
Option C:
$0.50 \Omega$
Option D:
$0.10 \Omega$

Answer: B

Step-by-step solution

$\mathrm{G}=200 \Omega$

$\mathrm{i}_{\mathrm{g}}=20 \mu \mathrm{~A}$ $i=i_{g}\left(\frac{G}{S}+1\right)$

$\Rightarrow 20 \times 10^{-3}=20 \times 10^{-6}\left(\frac{200}{\mathrm{~S}}+1\right)$

$\Rightarrow \frac{200}{\mathrm{~S}}=999$

$\Rightarrow \mathrm{S} \approx 0.2 \Omega$

Answer key and solution verified before publishing.

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Exam: JEE Main 2024
Paper: 9 April, Shift 1
Subject: Physics
Chapter: Current Electricity
Topic: Electrical Measuring Instruments

The current flowing through the 1 Omega resistor is frac n10 A. The value of n is .

Answer: B

Step-by-step solution

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