Free mock exam
Protection & Devices — 18th Edition (BS 7671) Practice
Free topic-focused mock exam: all 23 questions on Protection & Devices, drawn from the wider 18th Edition (BS 7671) bank. 60-minute timer, 70% to pass, worked explanation on every question. Use this when you've taken the full mock once and want to drill the topics you got wrong.
- Questions
- 23
- Time limit
- 60 min
- Pass mark
- 70% · 17/23
- Question bank
- 23
Free, no sign-up. Retake as many times as you like — the questions are reshuffled, with the answer order changed.
Sample questions
01Which regulation requires that circuits supplying portable outdoor equipment be RCD protected?
- ARegulation 643.1
- BRegulation 521.8
- CRegulation 314.1
- DRegulation 411.3.3
Why: Regulation 411.3.3 mandates RCD protection for circuits supplying portable outdoor equipment.
02What is the acceptable maximum disconnection time for a 30mA RCD on a TT system?
- A200 milliseconds
- B40 milliseconds
- C300 milliseconds
- D5 seconds
Why: For TT systems, the maximum disconnection time for RCDs is 300 milliseconds at rated residual current.
03How does BS 7671:2018+A4:2026 require the effectiveness of a 30mA RCD to be verified?
- ATests at ½x, 1x and 5x IΔn in sequence
- BThe integral test button alone
- CA test at 5x IΔn on both half-cycles
- DA single AC test at IΔn, whatever the RCD type
Why: Amendment 4 deleted Table 3A (time/current performance criteria for RCDs) from Appendix 3. Regulation 643.8 now calls for a single alternating current test at the rated residual operating current, IΔn, regardless of RCD type — AC, A, F or B. A general non-delay device must operate within 300ms. The 5x IΔn test still has a place in fault-finding, but it is no longer part of the required verification.
Common questions
Is the Protection & Devices mock exam free?
Yes — 100% free, no sign-up needed. Questions are pulled at random from a substantial bank, with a worked explanation on every question after you submit.
Can I retake the mock exam?
Yes. Every attempt picks a different random selection and reshuffles the options, so each retake gives you genuinely new questions. No limit on retakes.
Does this count towards the real qualification?
No — this is independent practice material. To gain the actual qualification you need to sit the official assessment through an approved provider.
