A student is reading a data sheet for an electronic component. The data sheet lists the following specifications: a capacitance of 470 μF, an operating voltage of 16 V, and a leakage current of 2 mA. The student needs to record all values in standard SI units for a report. Explain how the student should convert each of the three values into standard SI units, and state the name of each prefix used.

AQA A-Level Physics (7408) — 3.1.1 Use of SI Units and Their Prefixes · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (5 marks)

470 μF = 470 × 10⁻⁶ F (0.000470 F or 4.70 × 10⁻⁴ F);
16 V is already in SI units – no conversion needed;
2 mA = 2 × 10⁻³ A (0.002 A).

Examiner tips

  • Use the prefix–power‑of‑ten conversion for μ and m; show the equivalent value in base units; note that V is already SI; keep units consistent.
  • Write the full conversion (470 × 10⁻⁶ F) to demonstrate understanding of the prefix.

Mark scheme (5 marks)

  1. Identifies that μ (micro) means × 10⁻⁶ (or one millionth)
  2. Correctly converts 470 μF to 470 × 10⁻⁶ F (or 0.000470 F / 4.70 × 10⁻⁴ F)
  3. Identifies that m (milli) means × 10⁻³ (or one thousandth)
  4. Correctly converts 2 mA to 2 × 10⁻³ A (or 0.002 A)
  5. States that 16 V requires no conversion / is already in a standard SI unit with no prefix

Key terms in this question

SI units · prefix

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