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220-1201 Practice Question: A small office has several desktop PCs that…
A small office has several desktop PCs that intermittently fail to power on in the morning. The issue is more common on humid days. After checking the wall outlets, you find they are properly grounded. What is the most likely cause?
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 power supply units are failing due to moisture-related internal corrosion
A failing power supply can be sensitive to humidity, causing internal shorts or capacitor leakage. Inrush current from multiple PCs on the same circuit could also be a factor, but the humidity correlation points to PSU degradation. Proper grounding eliminates outlet issues.
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 power supply units are failing due to moisture-related internal corrosion
Why this is correct
Moisture-related internal corrosion within a Power Supply Unit (PSU) can degrade solder joints, capacitor leads, or trace pathways on the circuit board. This degradation increases electrical resistance and can lead to intermittent power delivery issues, especially when the system is cold or after prolonged periods of inactivity, as temperature changes can exacerbate poor connections. The intermittent nature arises because the corroded path might temporarily complete the circuit under certain conditions, only to fail again when conditions shift slightly, causing the PC to intermittently fail to power on.
- ✗
The building's circuit breaker is tripping due to overload
Why it's wrong here
A building's circuit breaker tripping due to overload indicates a complete interruption of power to the entire circuit, not an intermittent issue affecting individual PCs. If the breaker had tripped, none of the PCs on that circuit would power on until the breaker was manually reset, and the problem would not spontaneously resolve or be dependent on environmental factors like humidity. This scenario would result in a hard power outage rather than an intermittent startup failure.
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The CMOS battery is dead on each PC
Why it's wrong here
The CMOS battery's primary function is to maintain the BIOS settings and the Real-Time Clock (RTC) when the computer is powered off or unplugged. A dead CMOS battery typically results in the system losing its date and time settings upon reboot, or requiring a manual configuration of BIOS settings, but it does not prevent the fundamental power-on sequence of the PC itself. The power supply and motherboard still receive power, allowing the system to attempt to boot, albeit with potential configuration issues.
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The power button is stuck on each case
Why it's wrong here
A power button that is physically stuck in the 'on' position would continuously send a power-on signal to the motherboard, leading to either constant attempts to power on, immediate power-on upon connection to power, or an inability to power off. This condition would not manifest as intermittent startup failures, where the PC sometimes powers on and sometimes doesn't. Furthermore, it is highly improbable for the power buttons on multiple, separate desktop PCs to simultaneously become stuck in the same manner.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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