$AB$ is a wire of uniform resistance. The galvanometer $G$ shows no current when the length $AC = 20\,cm$ and $CB = 80\, cm$. The resistance $R$ is equal to .............. $\Omega $
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By Wheatstone bridge, $\frac{R}{{80}} = \frac{{AC}}{{BC}} = \frac{{20}}{{80}}$ $ \Rightarrow $ $R = 20\,\Omega $
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