A positively charged oil droplet falls in air in a uniform electric field that is vertically upwards. The droplet has a constant terminal speed v₀ and the electric field strength is E. The magnitude of the force due to air resistance acting on the droplet is proportional to the speed of the droplet. Which graph shows the variation with E of v₀?
✓ Correct Answer
The correct answer is A: Graph of v₀ against E, showing a straight line with negative gradient.
📋 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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