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JEE Main 20249 AprilMorning Shift

Exam: JEE Main
Year: 2024
Date: 9 April
Shift: Morning Shift
Subject: Physics
Chapter: Current Electricity

JEE Main 2024 · 9 April · Morning Shift · Physics · Current Electricity

A galvanmeter has a coil of resistance 200 with a full scale...

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 ;

Options

A $0.40 \Omega$
B $0.20 \Omega$
C $0.50 \Omega$
D $0.10 \Omega$

Correct answer

B. $0.20 \Omega$

Step-by-step solution

\begin{aligned} & \mathrm{G}=200 \Omega \\ & \mathrm{i}_{\mathrm{g}}=20 \mu \mathrm{A} \\ & \mathrm{i}=\mathrm{i}_{\mathrm{g}}\left(\frac{\mathrm{G}}{\mathrm{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\end{aligned}

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