A-LevelPhysicsCapacitanceOct/Nov 2021Paper 5 Q215 Marks
A student investigates the discharge of a capacitor in the circuit shown in Fig. 2.1. [Figure 2.1] The student closes the switch and charges the capacitor. The switch is opened and a stop-watch is started. The capacitor discharges through the two resistors of resistance R₁ and R₂ connected between P and Q. At a fixed time t the potential difference V across the capacitor is measured. The experiment is repeated for different values of R₁ and R₂. It is suggested that V, R₁ and R₂ are related by the equation In(V/E) = -t / (C(R₁ + R₂)) where E is the electromotive force (e.m.f.) of the battery and C is the capacitance of the capacitor.
📋 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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