Free notes
Number systems and prefixesIs a capital M the same as a small m?
Free from the notes: Sparky’s video on it, the section word for word as members see it, and a PDF to keep.
The notes
Exactly as they are on the site.
| Prefix | Symbol | Multiplier | Means | Example |
|---|---|---|---|---|
| Tera | T | ×10¹² | trillion | |
| Giga | G | ×10⁹ | thousand million | 1 GW = 1,000,000,000 W |
| Mega | M | ×10⁶ | million | 1 MΩ = 1,000,000 Ω |
| Kilo | k | ×10³ | thousand | 2 kW = 2000 W |
| base unit: V, A, Ω, W | ||||
| milli | m | ×10⁻³ | thousandth | 30 mA = 0.030 A |
| micro | µ | ×10⁻⁶ | millionth | 1 µA = 0.000001 A |
| nano | n | ×10⁻⁹ | thousand-millionth | |
| pico | p | ×10⁻¹² | trillionth | |
This is engineering notation: electricians work in powers of 3, so each step is ×1000. Moving to a bigger prefix makes the number smaller, and moving to a smaller prefix makes it bigger.
- Positive power (10⁶): the zeros go before the decimal point, so it's a big number. Negative power (10⁻⁶): the zeros go after the decimal point, so it's a tiny number.
- Capital M = mega (million) and small m = milli (thousandth). Mixing them up is a big mistake.
- You'll see MΩ when insulation resistance testing, and Ω when continuity testing.
Conversions
8.4 kW in watts → 8400 W 100 mA in amps → 0.1 A 0.03 A in milliamps → 30 mA 0.5 MΩ in kilo-ohms → 500 kΩ 80 mA in amps → 0.08 A (= 80 × 10⁻³)
Use the ×10ˣ key. For 80 mA, type 80 ×10ˣ −3. Also, 30 mA is the trip rating of an RCD, so you'll see that number a lot.
Free section from Sparky Study Notes. The full Level 3 notes, 1,463 practice questions and the video lessons: sparkystudynotes.co.uk
Test yourself on it
The tests are in the members’ area. Get one wrong and it shows you why, and where to revise.
Get new notes and exam tips from Sparky
About one email a fortnight. Unsubscribe any time. Privacy noticeThat was one section. There are 583.
Sparky Study Notes is the whole Level 3 syllabus written up like this: the explanation, the worked example, and where it is in your book. With a video lesson for every part and a practice paper for every exam.
- 583sections of written notes
- 35video lessons
- 1,463practice questions
- 146diagrams, redrawn
- 18th Edition
- Building Regs
- PAT
- Fundamental Inspection & Testing
- Initial Verification
- Periodic Inspection & Testing