Electric Current & Charge Flow — A/L Physics

How do I practise Electric Current & Charge Flow?

1 question with a worked solution

1. A copper wire of cross-sectional area A = 1.0 × 10⁻⁶ m² carries a steady current I = 3.2 A. If the free electron density in copper is n = 8.0 × 10²⁸ m⁻³ and electron charge is e = 1.6 × 10⁻¹⁹ C, what is the drift velocity v_d of conduction electrons in the wire?
   1. A) 2.5 × 10⁻⁴ m s⁻¹
   2. B) 2.5 × 10⁻² m s⁻¹
   3. C) 5.0 × 10⁻⁴ m s⁻¹
   4. D) 1.25 × 10⁻³ m s⁻¹
   Check my answer

   Correct answer: A) 2.5 × 10⁻⁴ m s⁻¹

   The relationship between electric current and electron drift velocity is I = n A e v_d. Rearranging: v_d = I / (n A e) = 3.2 A / [(8.0 × 10²⁸ m⁻³) × (1.0 × 10⁻⁶ m²) × (1.6 × 10⁻¹⁹ C)] = 3.2 / (1.28 × 10⁴) = 2.5 × 10⁻⁴ m s⁻¹.

   Show worked solution

   Step 1: Formula: v_d = I / (n · A · e). Step 2: v_d = 3.2 / (8.0 × 10²⁸ × 1.0 × 10⁻⁶ × 1.6 × 10⁻¹⁹) = 3.2 / 12,800 = 2.5 × 10⁻⁴ m s⁻¹. Answer: 2.5 × 10⁻⁴ m s⁻¹.
   Modelled on: the A/L Physics examination pattern

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Where does Electric Current & Charge Flow fit in the syllabus?

Unit 7.1 · Year 2 · Term 1