A-LevelPhysicsD.C. circuitsMay/June 2018Paper 1 Q371 Mark

A thermistor is an electrical component with a resistance that varies with temperature. A thermistor T is used in a fire alarm system. The alarm is triggered when the potential difference between X and Y is 4.5 V. [Diagram] What is the resistance of T when the alarm is triggered?

Q: What is the correct answer to this A-Level Physics question?

The correct answer is C: 250 Ω.

Q: What topic does this question test?

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

A90 Ω

B150 Ω

C250 Ω

D400 Ω

✓ Correct Answer

The correct answer is C: 250 Ω

📋 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 2018 examination, Paper 1 Variant 2.

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