A-LevelPhysicsElectricity9702/12 · May/June 2020 · Q331 Mark
The number density of free electrons in copper is 8.0 × 10²⁸ m⁻³. A copper wire has diameter 0.42 mm. What is the average drift speed of the free electrons in the wire when the current in the wire is 0.57 A?
A8.0 × 10⁻¹¹ m s⁻¹
B3.2 × 10⁻¹⁰ m s⁻¹
C8.0 × 10⁻⁵ m s⁻¹
D3.2 × 10⁻⁴ m s⁻¹
✓ Correct answer
D: 3.2 × 10⁻⁴ m s⁻¹
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