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:
JEE MAIN 2024, Diffcult
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$\mathrm{G}=200 \Omega$
$\mathrm{i}_{\mathrm{g}}=20 \mu \mathrm{A}$
$\mathrm{i}=\mathrm{i}_{\mathrm{g}}\left(\frac{\mathrm{G}}{\mathrm{S}}+1\right)$
$\Rightarrow 20 \times 10^{-3}=20 \times 10^{-6}\left(\frac{200}{\mathrm{~S}}+1\right)$
$\Rightarrow \frac{200}{\mathrm{~S}}=999$
$\Rightarrow \mathrm{S} \approx 0.2 \Omega$
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