Free mock exam

Free 2391-52 mock exam: a 20-question simulator with answers

Twenty original multiple-choice questions on inspection and testing, taken from our 2391-52 practice papers. Work through them one at a time with a timer running, flag the ones you are unsure of, then get your score by topic with every answer explained. No sign-up, no email.

The simulator covers all four areas of the book: the requirements for inspection and testing, safety management, inspection, and testing. Most of the questions are on testing, as they are in our full papers: test sequence, test methods, instruments and reading the results, including worked figures.

Each explanation says where to look in BS 7671:2018+A4:2026 or the guidance it comes from, so you can follow up anything you get wrong.

The questions are practice in the style of a multiple-choice inspection and testing paper. They are not copies of any real assessment, and nothing here states the real assessment’s duration, pass mark or topic weighting. Confirm the current details with your centre.

The mock exam

1. Under the Electricity at Work Regulations 1989, work on or near a live conductor, where danger may arise, is permitted only when:

Safety and legal requirements

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Answer A: it is unreasonable for the conductor to be dead, it is reasonable to work on or near it live, and suitable precautions are taken

Regulation 14 sets three conditions and all three must be met. Client convenience, a qualification or a short duration do not on their own justify live work.

Where to look: EAWR 1989 reg 14; HSE HSR25
Paper 1, question 1 in the book.

2. A consumer unit in a house is replaced. Which document must be issued on completion?

Certification and reporting

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Answer D: An Electrical Installation Certificate

Replacing a consumer unit or distribution board is an alteration that must be certified on an EIC, with its schedules. An EICR is never used to certify new work.

Where to look: BS 7671 reg 644.1; IET A4 model EIC notes; ESF BPG1
Paper 1, question 5 in the book.

3. A new final circuit is installed to supply an electric vehicle charge point. Which document is issued?

Certification and reporting

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Answer C: An Electrical Installation Certificate

Any addition that introduces a new circuit is certified on an EIC.

Where to look: IET A4 model EIC notes
Paper 2, question 5 in the book.

4. An Electrical Installation Condition Report assesses an installation against:

Periodic inspection

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Answer A: the edition of BS 7671 current at the time of the inspection

The report compares the installation with the current edition whatever its age. Not complying with the current edition does not, by itself, make an older installation unsafe.

Where to look: ESF Best Practice Guide 4, issue 7.4, s1 and s2
Paper 1, question 11 in the book.

5. Which device should be used to prove that a circuit is dead at the point of work?

Safe isolation

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Answer D: A proprietary two-pole voltage detector or test lamp, proved on a proving unit before and after use

Only a device that makes contact with the conductor may prove dead, and it must be proved before and after use. Multimeters are not recommended for this.

Where to look: HSE GS38 paras 13, 19, 20; ESF BPG2 s5
Paper 1, question 14 in the book.

6. Why should inspection normally be carried out before testing?

Inspection

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Answer A: Defects found on inspection may make testing dangerous or affect the results

A defect such as damaged insulation or a missing barrier could make a test hazardous or give misleading readings.

Where to look: ESF BPG10 s5
Paper 1, question 17 in the book.

7. During a periodic inspection, a socket-outlet has a broken faceplate and live terminals can be touched. Which classification code applies?

Observation coding

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Answer C: C1

Touchable live parts are a danger present now, so C1 applies. The person ordering the report must be told straight away, in writing.

Where to look: ESF BPG4 s6 and s9 (C1 examples)
Paper 1, question 22 in the book.

8. The incoming water service to a house is plastic, and the pipework inside is copper. What does this normally mean for main protective bonding?

Inspection

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Answer A: The internal pipes are not normally extraneous-conductive-parts, so main bonding is not normally needed

A plastic incoming service does not bring Earth potential into the building, so the copper pipes are not normally extraneous. Test if in doubt.

Where to look: BS 7671 reg 411.3.1.2 (as explained by IET)
Paper 2, question 18 in the book.

9. Incorrect polarity is found at the origin of the installation. Which code applies?

Observation coding

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Answer B: C1

Incorrect polarity at the origin is C1. Incorrect polarity at a final circuit, accessory or item of equipment is C2.

Where to look: ESF BPG4 s9
Paper 2, question 22 in the book.

10. On a new domestic installation with an RCBO on every circuit, which of these tests is carried out first?

Test sequence

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Answer A: Continuity of protective conductors

Dead tests come first, starting with continuity of protective conductors. Live tests come after the dead tests are satisfactory.

Where to look: BS 7671 regs 643.2 to 643.11; IET Wiring Matters 105
Paper 1, question 29 in the book.

11. In the three-step ring final circuit test, step 1 measures:

Test methods

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Answer B: the end-to-end resistance of the line, neutral and protective conductors of the ring

Step 1 gives r1, rn and r2. Steps 2 and 3 use the cross-connected ends.

Where to look: IET Wiring Matters 89 (March 2022)
Paper 1, question 36 in the book.

12. GS38 recommends that the exposed metal tip of a test probe is:

Test instruments

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Answer C: no more than 4 mm, with 2 mm or less strongly recommended

Short tips reduce the risk of a short circuit or flashover. Spring-loaded retractable screened probes are another option.

Where to look: HSE GS38 para 9
Paper 1, question 43 in the book.

13. Ze is 0.28 Ω and (R1 + R2) is 0.62 Ω. The designer's maximum Zs for comparison with test results (already corrected for conductor temperature) is 1.10 Ω. Which statement is correct?

Interpreting results

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Answer D: Zs = 0.90 Ω, which is within the maximum

Zs = Ze + (R1 + R2) = 0.28 + 0.62 = 0.90 Ω. The maximum given is already corrected, so no further factor is applied.

Where to look: IET Wiring Matters 105 (Zs = Ze + (R1 + R2))
Paper 1, question 49 in the book.

14. A 30 mA general (non-delay) RCD operates in 46 ms when tested at IΔn. The result is:

Interpreting results

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Answer C: a pass, because it is within the 300 ms maximum

At IΔn the maximum for a general non-delay RCD is 300 ms, the time its product standard sets and manufacturers' instructions state. The 40 ms figure belongs to the 5 × IΔn test, which BS 7671 no longer requires.

Where to look: Manufacturer's instructions (BS EN 61008-1 times); IET Wiring Matters 91
Paper 1, question 53 in the book.

15. Why must SPDs normally be disconnected before an insulation resistance test?

Test methods

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Answer D: They are likely to affect the result or be damaged by the test

Equipment likely to influence or be damaged by the test is disconnected first. At initial verification the cables are tested before such equipment is connected, with a further test at a reduced voltage after connection.

Where to look: IET Inspection and Testing FAQs; NICEIC, insulation resistance testing changes (2024)
Paper 2, question 37 in the book.

16. Functional testing at the consumer unit includes:

Test methods

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Answer C: operating the main switch, and manually operating circuit-breakers and RCDs, to show they work and disconnect

BS 7671 does not require circuit-breakers to be tested as products. Manual operation is checked.

Where to look: BS 7671 reg 643.10; IET A4 model EICR items 4.7 and 4.8
Paper 2, question 38 in the book.

17. What does BS 7671 require about calibration of test instruments?

Test instruments

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Answer B: It does not require regular calibration, but there should be a system to confirm and record their continuing accuracy

ESF describes options such as formal recalibration, a checkbox, cross-checks between instruments and reference resistors, with results recorded.

Where to look: ESF BPG7 s1 and s3
Paper 2, question 44 in the book.

18. Three circuits tested together read 4 MΩ. Two of them, tested separately, read 20 MΩ and 10 MΩ. What is the insulation resistance of the third circuit?

Interpreting results

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Answer C: 10 MΩ

1 ÷ R = 1/4 − 1/20 − 1/10 = 0.25 − 0.05 − 0.10 = 0.10, so R = 10 MΩ. Parallel readings cannot simply be added or subtracted.

Where to look: Principles (resistances in parallel)
Paper 2, question 50 in the book.

19. Ze = 0.30 Ω and the circuit (R1 + R2) = 0.45 Ω. Taking 230 V, what is the prospective earth fault current at the end of the circuit, to the nearest amp?

Interpreting results

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Answer A: 307 A

Z = 0.30 + 0.45 = 0.75 Ω; I = 230 ÷ 0.75 = 307 A. Using Ze alone gives the value at the origin.

Where to look: Principles (Ohm's law)
Paper 2, question 55 in the book.

20. A 100 mA time-delayed (S-type) RCD operates in 180 ms when tested at IΔn. The result is:

Interpreting results

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Answer B: a pass, because it is within the 130 ms to 500 ms range

For a time-delayed RCD at its rated residual current, the operating time must be at least 130 ms and no more than 500 ms, the times its product standard sets.

Where to look: Manufacturer's instructions (BS EN 61008-1 times); IET Wiring Matters 91
Paper 2, question 58 in the book.

Your score

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The full papers: 120 questions and 16 written scenarios

All twenty questions are from Inspection and Testing Exam Practice (2391-52): two full 60-question multiple-choice papers, 120 original questions with an explanation and a where-to-look reference for every answer, plus 16 written scenarios with model answers and marking points.

Paperback on Amazon: £14.99Kindle on Amazon: £9.99

Sold on Amazon.co.uk. Amazon links are affiliate links. Kindle edition free to read with Kindle Unlimited. Read a free sample on Amazon before you buy.

The 2391-52 mock on your iPhone

The 2391-52 Inspection Mock app has all 120 multiple-choice questions from the book: a 20-question mock, both 60-question papers with a clock and a question grid, practice by topic, and a mistakes review that brings back what you got wrong. Every answer is explained. It works offline and needs no account.

Get the app on the App Store

Free to download, with the 20-question mock open to everyone. One purchase of £19.99 unlocks the rest; no subscription. Needs iOS 18 or later.

For the written side, try a free 2391-52 written scenario with its model answer. For the sums, the max Zs calculator and Inspection and Testing Calculations.

Independent publication. Not produced, endorsed or approved by City & Guilds, the IET or BSI. Not a past paper and contains no assessment questions.

Written by a City & Guilds 2391-51 qualified electrician.