A cell with electromotive force (e.m.f.) $E$ and internal resistance $r$ is connected to a variable resistor, as illustrated. The resistance of the variable resistor is increased steadily from $r$ to $3r$. Which graph shows how the potential difference (p.d.) $v$ across the internal resistance varies with the p.d. $V$ across the variable resistor?
Physics 9702 · AS & A Level · Potential difference and power