A-LevelPhysicsD.C. circuits9702/12 · Oct/Nov 2019 · Q351 Mark

A battery has an electromotive force (e.m.f.) E and internal resistance r. The battery delivers a current I to a variable resistor and the potential difference (p.d.) across its terminals is V. [Figure showing a battery with e.m.f. E and internal resistance r connected to a variable resistor, with current I and terminal p.d. V indicated.] The variable resistor is adjusted so that I increases. Why does V decrease?

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AThe e.m.f. E decreases.

BThe internal resistance r increases.

CThe p.d. across r increases.

DThe resistance of the variable resistor increases.

✓ Correct answer

C: The p.d. across r increases.

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Topic: D.C. circuits, A-Level Physics (syllabus 9702). Multiple choice, 1 mark.
Source: A-Level Physics, Oct/Nov 2019 Paper 1 Variant 2, question 35.

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