A-LevelPhysicsD.C. circuitsOct/Nov 2022Paper 1 Q371 Mark
A potential divider circuit is designed to detect the difference in temperature between two different places. [Figure showing a potential divider circuit with thermistors X and Y and a voltmeter] The cell has electromotive force (e.m.f.) 20 mV and negligible internal resistance. Initially, thermistors X and Y are at the same temperature and have the same resistance. The voltmeter reads 10mV. X is then placed in a cold environment and its resistance doubles. Y is placed in a warm environment and its resistance halves. What is the new reading on the voltmeter?
A4mV
B5mV
C15mV
D16 mV
✓ Correct Answer
The correct answer is A: 4mV
📋 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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