A cell having an emf $\varepsilon$ and internal resistance $r$ is connected across a variable external resistance $R.$ As the resistance $R$ is increased, the plot of potential difference $V$ across $R$ is given by
AIPMT 2012,NEET 2017, Medium
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Current in the circuit, $I=\frac{\varepsilon}{R+r}$
Potential difference across $R$
${V=I R=\left(\frac{\varepsilon}{R+r}\right) R} $
${V=\frac{\varepsilon}{1+\frac{r}{R}}}$
When $R=0, V=0$
$R=\infty, V=\varepsilon$
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