When the resistance $R$ (indicated in the figure below) is changed from $1 \,k \Omega$. to $10 \,k \Omega$, the current flowing through the resistance $R'$ does not change. What is the value of the resistor $R'?$
KVPY 2021, Diffcult
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(B)

Current through $R$ will not change only when wheatstone bridge is formed

$\Rightarrow \frac{1 K \Omega}{10 K \,\Omega}=\frac{ R ^{\prime}}{1 K \Omega}$

$\Rightarrow R ^{\prime}=100 \,\Omega$

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