What factors affect the current-carrying capacity of a cable?

Current-carrying capacity depends on installation method (Appendix 4), ambient temperature (Ca), grouping (Cg), and thermal insulation (Ci).

Conductor colour, length and number of cores

Supply voltage, frequency and earthing system

Circuit protective device type and breaking capacity

Installation method, ambient temperature, grouping, thermal insulation

What is the minimum cable cross-sectional area for lighting circuits?

The minimum conductor size for lighting circuits is generally 1.0mm² for copper conductors.

What is the minimum cable size for socket outlet circuits using ring final circuit design?

Ring final circuits are typically wired in 2.5mm² cable, protected by a 32A device.

Free mock exam

BS7671 Selection & Erection — AM2 Online Knowledge Test Practice

Free topic-focused mock exam: 15 random questions from a pool of 31 on BS7671 Selection & Erection, drawn from the wider AM2 Online Knowledge Test bank. 25-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: 15
Time limit: 25
Pass mark: 70%
Bank size: 31

Free · no sign-up · timer can be ignored · retake as many times as you want

Sample questions

01What factors affect the current-carrying capacity of a cable?
- A.Supply voltage, frequency and earthing system
- B.Installation method, ambient temperature, grouping, thermal insulation
- C.Circuit protective device type and breaking capacity
- D.Conductor colour, length and number of cores
Why: Current-carrying capacity depends on installation method (Appendix 4), ambient temperature (Ca), grouping (Cg), and thermal insulation (Ci).
02What is the minimum cable cross-sectional area for lighting circuits?
- A.1.0mm²
- B.2.5mm²
- C.0.5mm²
- D.1.5mm²
Why: The minimum conductor size for lighting circuits is generally 1.0mm² for copper conductors.
03What is the minimum cable size for socket outlet circuits using ring final circuit design?
- A.1.0mm²
- B.2.5mm²
- C.4.0mm²
- D.1.5mm²
Why: Ring final circuits are typically wired in 2.5mm² cable, protected by a 32A device.

FAQ

Is the BS7671 Selection & Erection 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.