Question

$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

• A.
• B.
• C.
• D.

Answer 1

Answer: (C)

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 $R=0, V=0$
$R=\infty, V=\varepsilon$