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Worked examples and guides for electricians
Free articles with worked examples taken from the books, with the same working and rounding. Our BS 7671 guides name the published source for every point.
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- Free toolMax Zs calculatorWork out the maximum Zs for a device from Ia, and check a circuit from Ze and (R1 + R2), including cold readings.
- BS 7671 guideBS 7671:2018+A4:2026 is now in force: what changedBS 7671:2018+A4:2026 replaced the A2+A3 version on 15 October 2026. The main changes, what changes on EICRs and certificates, and a checklist, with sources.
- Worked examplesHow to calculate maximum Zs: worked examplesHow to work out maximum earth fault loop impedance (Zs) from the device current, with three worked examples and how to check a circuit complies.
- Practice questionsBS 7671 A4:2026: 10 free practice questions with answersTen multiple-choice questions on BS 7671:2018+A4:2026 with answers, short explanations and where to look in the book. Taken from our practice papers.
- Electrical scienceElectrical science for apprentices: power factor explained with a worked exampleWhat power factor means, the power triangle formulas, a worked example from motor test readings, and why a better power factor means less current.