A cell having an $\operatorname{emf} \varepsilon$ and internal resistance $r$ is connected across a variable…
A cell having an $\operatorname{emf} \varepsilon$ 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
Solution
Here, $E=I(R+r) \Rightarrow E=I R+I r$ and
$\begin{aligned}
& E=V+I r \\
& E=V+\frac{E r}{R+r} \\
& V=E-\frac{E}{R+r} \times r \\
& y=c-\frac{1}{x}
\end{aligned}$
This equation represents option (3).
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