A-LevelPhysicsD.C. circuitsOct/Nov 2025Paper 1 Q361 Mark
A potentiometer circuit is used to determine the electromotive force (e.m.f.) E_X of a cell. The circuit includes a second cell of known e.m.f. E₀ and negligible internal resistance, and a uniform resistance wire PQ of known length. E_X is less than E₀. The movable connection J can be positioned anywhere along the length of the resistance wire. Which circuit is suitable for determining E_X?
A[Diagram option A]
B[Diagram option B]
C[Diagram option C]
D[Diagram option D]
✓ Correct Answer
The correct answer is D: [Diagram option D]
📋 Examiner Report & Trap Analysis
Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
🎯 Mark Scheme Breakdown
Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.
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