A-LevelPhysicsD.C. circuitsFeb/Mar 2021Paper 1 Q361 Mark
A cell that has internal resistance is connected to a switch S and a variable resistor. A voltmeter is connected between the terminals of the cell, as shown. [Figure 36.1] When switch S is open, the voltmeter reads 1.5 V. The switch is then closed and the variable resistor is adjusted to have a resistance of 4.0 Ω. The voltmeter now reads 0.75 V. What is the internal resistance of the cell?
A1.0 Ω
B2.0 Ω
C4.0 Ω
D8.0 Ω
✓ Correct Answer
The correct answer is C: 4.0 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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