Free mock exam
Common Faults — Level 3 Fault Diagnosis Practice
Free topic-focused mock exam: 30 random questions from a pool of 35 on Common Faults, drawn from the wider Level 3 Fault Diagnosis bank. 35-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
- 30
- Time limit
- 35 min
- Pass mark
- 70% · 21/30
- Question bank
- 35
Free, no sign-up. Retake as many times as you like — different questions each time.
Sample questions
01A common cause of RCD nuisance tripping in damp environments is:
- AMoisture causing earth leakage on circuits
- BReversed polarity at the consumer unit
- CA shared neutral between two lighting circuits
- DA break in the line conductor before the load
Why: Moisture on insulation or in equipment reduces insulation resistance, causing earth leakage current that triggers the RCD.
02Flickering LED lights can commonly be caused by:
- AA high resistance joint in the protective conductor
- BA missing earth connection at the fitting
- CIncompatible dimmer switch or loose connection
- DA neutral borrowed from the adjacent circuit
Why: LED flickering is often caused by incompatible dimmer switches (designed for incandescent) or loose connections causing voltage variation.
03A circuit breaker that trips randomly, especially in warm weather, may have:
- AA fault in the thermal trip mechanism
- BA protective device of too low a breaking capacity
- CA loose neutral bar screw at the consumer unit
- DA complete open circuit in the protective conductor
Why: Thermal trip mechanisms can become sensitive or fail, tripping at lower than rated current, especially when ambient temperature is high.
Common questions
Is the Common Faults 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.
