Inspection and Testing Calculations
200 calculation questions on inspection and testing, each with a full worked answer.
For UK electricians and apprentices
Practise the method.
Check every step.
Calculation workbooks with a full worked answer for every question, and practice papers with an explanation for every answer. A4 PDFs: print the pages you need.
Written by a City & Guilds 2391-51 qualified electrician.
WORKBOOK Q53 · COREWorked answer
A protective device operates within the required disconnection time when the fault current is at least 200 A (Ia). Ze = 0.35 Ω, (R1 + R2) at 20 °C = 0.80 Ω, multiplier to operating temperature 1.20. Does the circuit comply?
Zs(max) = (230 × 0.95) ÷ 200= 218.5 ÷ 200 = 1.0925 ΩHot (R1 + R2) = 0.80 × 1.20 = 0.960 ΩZs = 0.35 + 0.960 = 1.31 Ω
1.31 Ω > 1.0925 Ω · does not comply
The books
Four practice books
Two calculation workbooks and two sets of practice papers. Each book page shows the full contents and sample pages from the PDF.
Buying opens shortly. Meanwhile, get the free 10-question sampler.
Electrical Science Calculations
200 electrical science questions for apprentices, from Ohm’s law to three-phase and motors.
BS 7671 A4:2026 Practice Papers
Three 60-question multiple-choice papers on BS 7671:2018+A4:2026, with explanations.
Inspection and Testing Practice Papers
Two 60-question mock tests and 16 written scenarios with marking points, for the 2391-52.
Bundle
Electrician Study Bundle: all four PDFs for £34.99
£49.96 if bought separately, so you save £14.97.
How the books work
Practise the method, then check every step
- Calculation questions give you all the data they need, so you practise the method rather than looking up tables
- Every worked answer shows the formula, the numbers and the result, with the same rounding you would use on a calculator
- Workbook questions are graded Easy, Core and Challenging, with a method page or notes at the start of each section
- Practice papers come with answer sheets, an answer key, a score record by topic and an explanation for every answer
Free sampler
Ten questions. Full worked answers.
Ten questions from Inspection and Testing Calculations, one from each of ten topics, each with the formula, the numbers and the result shown in full. A4 PDF, 7 pages.
It is a free product on Payhip. Payhip asks for your email address so it can send you the file.
- Continuity of protective conductors
- Ring final circuits
- Earth fault loop impedance
- Temperature adjustment
- Prospective fault current
- Insulation resistance
- RCD testing
- Voltage drop
- Design current and cable selection
- The adiabatic equation
Free learning
Worked examples, guides and a free calculator
- 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.
Questions
Before you buy
Who are the books for?
UK electricians and apprentices. The calculation workbooks suit anyone studying inspection and testing or electrical science, and anyone who wants to check their own working. The practice papers are for electricians preparing for open-book assessments on BS 7671:2018+A4:2026 and for the 2391-52 inspection and testing assessments.
Are they published by City & Guilds, EAL, the IET or BSI?
No. Independent publication. Not produced, endorsed or approved by City & Guilds, EAL, the IET or BSI. Not a past paper and contains no assessment questions.
Are these real assessment questions?
No. Every question is original. The practice papers are written in the style of a multiple-choice test, but they are not a past paper and contain no assessment questions. Confirm the current assessment details with your centre.
Do I need my own copy of BS 7671?
For the two calculation workbooks, no: all the data each question needs is given in the question. For the two sets of practice papers, yes: you will need your own copy of BS 7671:2018+A4:2026, because finding the answer in the book is the skill being practised.
What format are they?
A4 PDFs. Print the pages you need. Inspection and Testing Calculations is 128 pages, Electrical Science Calculations 114, the BS 7671 A4:2026 Practice Papers 53, and the Inspection and Testing Practice Papers 64.
How are the answers checked?
In both calculation workbooks every numerical answer was calculated by computer and checked by a second, independent calculation. In the Inspection and Testing Practice Papers every calculated answer was checked the same way. Every answer in the BS 7671 A4:2026 Practice Papers has a where-to-look reference to BS 7671 and the published source it was checked against.
How do I buy, and how does the free sampler work?
Buying opens shortly. When it does, every buy button will go to the product on Payhip, which handles the payment and the download. The free sampler is a free Payhip product: Payhip asks for your email address so it can send you the file.
Can I use the figures for real work?
No. All figures in the books are supplied for practice. No figure may be used for design, installation, inspection, testing or certification. Always use the current edition of BS 7671 and the manufacturer’s data.