- A
The PSU fan bearing is failing.
Why wrong: A failing fan bearing would produce a grinding or rattling noise, not a high-pitched whine, and would likely be intermittent or constant, not load-dependent.
- B
The PSU is experiencing coil whine due to electrical resonance.
Coil whine is caused by vibrations in the PSU's inductors under certain electrical loads; it is normal and not a sign of failure.
- C
The PSU is overheating and the thermal protection is activating.
Why wrong: Overheating would trigger fan speed increases or shutdowns, not produce a high-pitched whine; temperatures are reported as normal.
- D
The PSU has a loose internal component rattling.
Why wrong: A loose component would cause a rattling sound, not a consistent high-pitched whine, and would likely be present at all times.
220-1101 Power Supply Practice Question
This 220-1201 practice question tests your understanding of power supply. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A technician is troubleshooting a PC that emits a high-pitched whining noise under load. The noise is coming from the power supply area. The system is stable and temperatures are normal. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The PSU is experiencing coil whine due to electrical resonance.
Coil whine is a common phenomenon in power supplies and other components when electrical current passes through inductors, causing them to vibrate at audible frequencies. It is typically harmless and does not indicate a defect, though it can be annoying. If the system is stable, no replacement is needed.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The PSU fan bearing is failing.
Why it's wrong here
A failing fan bearing would produce a grinding or rattling noise, not a high-pitched whine, and would likely be intermittent or constant, not load-dependent.
- ✓
The PSU is experiencing coil whine due to electrical resonance.
Why this is correct
Coil whine is caused by vibrations in the PSU's inductors under certain electrical loads; it is normal and not a sign of failure.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
OSPF neighbours must agree on key parameters.
- ✗
The PSU is overheating and the thermal protection is activating.
Why it's wrong here
Overheating would trigger fan speed increases or shutdowns, not produce a high-pitched whine; temperatures are reported as normal.
- ✗
The PSU has a loose internal component rattling.
Why it's wrong here
A loose component would cause a rattling sound, not a consistent high-pitched whine, and would likely be present at all times.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
- OSPF neighbours must agree on key parameters.
- Router ID selection can affect neighbour relationships and LSDB output.
- OSPF cost influences the preferred path.
- A route can appear in OSPF information but not become the installed route.
TExam Day Tips
- Check area mismatch first when OSPF adjacency fails.
- Review passive interfaces when a network is advertised but no neighbour forms.
- Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Real-world example
How this comes up in practice
A practitioner preparing for the 220-1201 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 220-1201 OSPF questions on adjacency and route selection.
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FAQ
Questions learners often ask
What does this 220-1201 question test?
Power Supply — This question tests Power Supply — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The PSU is experiencing coil whine due to electrical resonance. — Coil whine is a common phenomenon in power supplies and other components when electrical current passes through inductors, causing them to vibrate at audible frequencies. It is typically harmless and does not indicate a defect, though it can be annoying. If the system is stable, no replacement is needed.
What should I do if I get this 220-1201 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 220-1201 OSPF questions on adjacency and route selection.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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Last reviewed: Jun 18, 2026
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