Physics (AS & A Level) · Feb / March 2019 · Paper 12 · Question 36

A cell of internal resistance r and electromotive force (e.m.f.) E is connected in series with a resistor of resistance R. The resistance R and the e.m.f. E remain fixed. The internal resistance r of the cell changes over time. Which graph best shows the variation of the current I in the circuit with the internal resistance r?

1. AGraph of I against r: curve starting high on the I-axis and decreasing, approaching zero as r increases.
2. BGraph of I against r: curve starting at a finite value on the I-axis and decreasing towards zero as r increases.
3. CGraph of I against r: straight line with negative gradient starting from a finite value on the I-axis.
4. DGraph of I against r: horizontal straight line at constant I.

As printed in the paper