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A-LevelPhysicsD.C. circuitsMay/June 2011Paper 1 Q371 Mark

The diagram shows a fixed resistor and a light-dependent resistor (LDR) in series with a constant low-voltage supply. When the LDR is in the dark, the fixed resistor and the LDR have the same value of resistance. Light is shone on the LDR. What happens to the potential differences across the two components?

Ap.d. across resistor: decreased, p.d. across LDR: increased
Bp.d. across resistor: increased, p.d. across LDR: decreased
Cp.d. across resistor: no change, p.d. across LDR: increased
Dp.d. across resistor: no change, p.d. across LDR: decreased

✓ Correct Answer

The correct answer is B: p.d. across resistor: increased, p.d. across LDR: decreased

📋 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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About This A-Level Physics Question

Topic

This multiple-choice question tests D.C. circuits in A-Level Physics (syllabus code 9702). It is worth 1 mark.

Source

This question appeared in the Cambridge A-Level Physics May/June 2011 examination, Paper 1 Variant 2.

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