220-1101 Mobile Devices Practice Question
A user reports that their iPhone charges very slowly when connected to a USB port on their laptop, but charges normally using the included wall adapter. The cable is known to be functional. Which of the following is the MOST likely cause?
⚠ Common exam trap
Test-takers frequently confuse a software or driver issue with a hardware power delivery limitation, overlooking the fundamental current output difference between USB ports and wall adapters.
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 laptop's USB port is a USB 2.0 port outputting lower current
USB ports on laptops, especially USB 2.0 ports, are typically limited to 500 mA (0.5 A) of current per the USB 2.0 specification. iPhones require higher current (typically 1 A or more) for fast charging, and the wall adapter provides that higher current. The slow charging is due to the laptop's USB port being unable to supply enough current, not a cable or software issue.
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 laptop's USB port is a USB 2.0 port outputting lower current
Why this is correct
USB 2.0 standard downstream ports are current-limited to 500 mA (0.5 A) at 5 V, delivering 2.5 W. An iPhone typically draws 1 A (5 W) from a wall charger, so when connected to this laptop port, it can only pull half its normal current, roughly halving charging speed. Even if the phone is idle, the battery will charge much slower than from a dedicated adapter.
- ✗
The iPhone's Lightning port is damaged
Why it's wrong here
If the iPhone's Lightning port were physically damaged, you would see symptoms that are not isolated to one host: the cable would fit loosely, the connection would be intermittent when the cable is jiggled, or the phone would fail to charge on any power source, including wall adapters. Since the phone charges normally (though slowly) from the laptop and presumably fine from a wall adapter, the port itself is functioning as a reliable electrical connection. The slow charge here is a power supply capability issue, not a connector integrity issue.
When this WOULD be correct
If the question stated that the iPhone does not charge at all when connected to any charger or computer, and the cable is known to be functional, then a damaged Lightning port would be the most likely cause.
- ✗
The laptop's USB driver is outdated
Why it's wrong here
Outdated USB drivers primarily affect device enumeration, data transfer stability, and feature recognition—they do not change the hardware's current-sourcing capability. While a driver could theoretically limit dynamic charging negotiation on modern USB Power Delivery ports, this laptop's USB 2.0 port is a standard downstream port that provides a fixed 0.5 A by hardware design. An old driver would likely cause Windows to fail to recognize the iPhone or show an error, not make it draw less current.
When this WOULD be correct
A user reports that an iPhone is not recognized by a laptop when connected via USB, but works with other computers. The cable and iPhone are known functional. In this case, an outdated or corrupted USB driver could be the cause of the detection failure.
- ✗
The iPhone's battery needs calibration
Why it's wrong here
A battery calibration procedure only updates the software's assessment of the battery's state of charge and full capacity, which is why it fixes false percentage readings or sudden shutdowns at high percentages. It does not alter the electrical current accepted by the battery nor the voltage provided by the USB port. Since the phone is charging at a steady (but slow) rate, calibration is irrelevant; the physical rate of charge is limited by the port's current delivery, not by the fuel gauge's calculation.
When this WOULD be correct
A user reports that their iPhone shows an incorrect battery percentage (e.g., jumps from 30% to 50% after restart) and the device occasionally shuts down unexpectedly despite showing remaining charge. In that scenario, battery calibration would be the likely fix.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 220-1101 exam frequently reuses these exact scenarios with slightly different constraints.
✓The laptop's USB port is a USB 2.0 port outputting lower currentCorrect answer▾
Why this is correct
USB 2.0 standard downstream ports are current-limited to 500 mA (0.5 A) at 5 V, delivering 2.5 W. An iPhone typically draws 1 A (5 W) from a wall charger, so when connected to this laptop port, it can only pull half its normal current, roughly halving charging speed. Even if the phone is idle, the battery will charge much slower than from a dedicated adapter.
✗The iPhone's Lightning port is damagedWrong answer — click to see why▾
Why this is wrong here
The cable is known to be functional, and the iPhone charges normally with the wall adapter, so the Lightning port is not damaged. The issue is specific to the laptop's USB port output.
★ When this WOULD be the correct answer
If the question stated that the iPhone does not charge at all when connected to any charger or computer, and the cable is known to be functional, then a damaged Lightning port would be the most likely cause.
Why candidates choose this
Candidates may assume that slow charging indicates a hardware problem with the charging port, especially if they have experienced port damage in the past, without considering the power output differences between USB ports and wall adapters.
✗The laptop's USB driver is outdatedWrong answer — click to see why▾
Why this is wrong here
An outdated USB driver could cause connectivity issues, but it would not selectively affect charging speed only via laptop USB ports while the wall adapter works fine. The symptom points to a power output limitation, not a driver problem.
★ When this WOULD be the correct answer
A user reports that an iPhone is not recognized by a laptop when connected via USB, but works with other computers. The cable and iPhone are known functional. In this case, an outdated or corrupted USB driver could be the cause of the detection failure.
Why candidates choose this
Candidates may think that software drivers control all USB functionality, including power delivery, and assume an outdated driver could reduce charging current, overlooking that USB power output is primarily hardware-limited.
✗The iPhone's battery needs calibrationWrong answer — click to see why▾
Why this is wrong here
Battery calibration addresses inaccurate charge level reporting, not slow charging speed. The issue is current delivery, not battery management.
★ When this WOULD be the correct answer
A user reports that their iPhone shows an incorrect battery percentage (e.g., jumps from 30% to 50% after restart) and the device occasionally shuts down unexpectedly despite showing remaining charge. In that scenario, battery calibration would be the likely fix.
Why candidates choose this
Candidates may confuse symptoms of battery aging or calibration issues with charging speed problems, or they may have heard that calibration can improve charging behavior in some devices.
Analysis generated from the official 220-1101blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1101 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 220-1101 exam.