A-LevelPhysicsD.C. circuits9702/12 · May/June 2011 · Q341 Mark

A source of electromotive force (e.m.f.) E has a constant internal resistance r and is connected to an external variable resistor of resistance R. As R is increased from a value below r to a value above r, which statement is correct?

AThe terminal potential difference remains constant.

BThe current in the circuit increases.

CThe e.m.f. of the source increases.

DThe largest output power is obtained when R reaches r.

✓ Correct answer

D: The largest output power is obtained when R reaches r.

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Topic: D.C. circuits, A-Level Physics (syllabus 9702). Multiple choice, 1 mark.
Source: A-Level Physics, May/June 2011 Paper 1 Variant 2, question 34.

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