What indicates a spur on a ring final circuit during testing?

Sockets on the ring read approximately equal; a spur shows a noticeably higher reading because of the extra non-ring cable length to it.

Identical readings at every socket on the ring

One socket with a higher resistance reading

An infinite reading at the consumer unit

A zero reading between line and neutral

The maximum length of 2.5mm² cable for a 32A ring final circuit is approximately:

A 32A ring final in 2.5mm² cable should not exceed approximately 100 metres total cable length.

For a circuit other than lighting, voltage drop should not exceed what percentage of nominal voltage?

The recommended limits are 3% for lighting circuits and 5% for other uses (for an installation supplied directly from a public distribution network).

Free mock exam

Cables & Containment — 18th Edition (BS 7671) Practice

Free topic-focused mock exam: all 8 questions on Cables & Containment, 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: 8
Time limit: 60 min
Pass mark: 70% · 6/8
Question bank: 8

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

Sample questions

01What indicates a spur on a ring final circuit during testing?
- AA zero reading between line and neutral
- BAn infinite reading at the consumer unit
- COne socket with a higher resistance reading
- DIdentical readings at every socket on the ring
Why: Sockets on the ring read approximately equal; a spur shows a noticeably higher reading because of the extra non-ring cable length to it.
02The maximum length of 2.5mm² cable for a 32A ring final circuit is approximately:
- A120 metres
- B50 metres
- C100 metres
- D70 metres
Why: A 32A ring final in 2.5mm² cable should not exceed approximately 100 metres total cable length.
03For a circuit other than lighting, voltage drop should not exceed what percentage of nominal voltage?
- A10%
- B15%
- C3%
- D5%
Why: The recommended limits are 3% for lighting circuits and 5% for other uses (for an installation supplied directly from a public distribution network).

Common questions

Is the Cables & Containment 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.