Emergency lighting systems should be tested:

Emergency lighting must be tested by simulating loss of the normal supply, confirming the luminaires illuminate and run for their rated duration (BS 5266).

By simulating mains failure to verify operation

Only with the normal supply fully energised

At 500V DC insulation resistance only

By measuring phase rotation at the luminaire

The touch voltage in accessible areas should not exceed:

Touch voltage should generally not exceed 50V in dry conditions for safety.

What is the purpose of applying diversity in electrical design?

Diversity recognises that not all connected loads operate at full demand simultaneously, allowing economic sizing of the supply and main cables.

To ensure every circuit is rated for full load at once

To account for not all loads operating simultaneously

To increase the prospective fault current for fast tripping

To provide a second independent supply to the installation

Free mock exam

Design & Selection — 18th Edition (BS 7671) Practice

Free topic-focused mock exam: all 11 questions on Design & Selection, 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: 11
Time limit: 60 min
Pass mark: 70% · 8/11
Question bank: 11

Free, no sign-up. Retake as many times as you like — the questions are reshuffled, with the answer order changed.

Sample questions

01Emergency lighting systems should be tested:
- ABy measuring phase rotation at the luminaire
- BAt 500V DC insulation resistance only
- CBy simulating mains failure to verify operation
- DOnly with the normal supply fully energised
Why: Emergency lighting must be tested by simulating loss of the normal supply, confirming the luminaires illuminate and run for their rated duration (BS 5266).
02The touch voltage in accessible areas should not exceed:
- A50V
- B25V
- C110V
- D230V
Why: Touch voltage should generally not exceed 50V in dry conditions for safety.
03What is the purpose of applying diversity in electrical design?
- ATo ensure every circuit is rated for full load at once
- BTo increase the prospective fault current for fast tripping
- CTo provide a second independent supply to the installation
- DTo account for not all loads operating simultaneously
Why: Diversity recognises that not all connected loads operate at full demand simultaneously, allowing economic sizing of the supply and main cables.

Common questions

Is the Design & Selection 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.