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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?
⚠ Common exam trap
220-1201 often tests the tendency to blame external power (breakers, outlets) or CMOS batteries for power-on issues, when humidity-correlated intermittent failures point to internal PSU moisture damage.
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
Intermittent power-on failures that are more common on humid days point to moisture-related issues inside the power supply unit. Humidity can cause condensation, leading to corrosion or short circuits within the PSU, which intermittently prevents the system from powering on. Since the outlets are properly grounded, the issue is likely internal to the PSUs.
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.
- ✗
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.
- ✗
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.
Go deeper
Related to this question
Learn chapter
Troubleshoot: Overheating and Thermal Issues
Key term
Power supply unit
A power supply unit (PSU) is the hardware component that converts electricity from a wall outlet into usable power for a computer's internal components.
Key term
CAN
A CAN (Controller Area Network) is a robust vehicle bus standard designed to allow microcontrollers and devices to communicate with each other without a host computer.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
This 220-1201 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 220-1201 exam.