220-1101 Mobile Devices Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✓

  Battery

  Why this is correct

  A faulty battery is the primary suspect for a 'plugged in, not charging' message because the battery's internal battery management system (BMS) can report a bad cell or an over-voltage condition, prompting the embedded controller to halt charging to prevent damage. Even while the AC adapter delivers correct voltage, a battery with elevated internal resistance or a defective smart-bus (SMBus) cannot accept a charge properly, so the laptop deliberately withholds charging power. This is the most often replaced component when this symptom appears with a known-good adapter.

• ✗

  DC power jack

  Why it's wrong here

  A failing DC jack almost always manifests as intermittent total power loss, such as the laptop abruptly shutting off or the charge indicator flickering when the power plug is wiggled, rather than a steady 'plugged in, not charging' warning. Since the laptop is clearly recognizing AC power and running, the jack is making solid electrical contact, meaning the occasional disconnect that a worn jack could cause would simply cut power to the whole system. Thus, the DC jack is an improbable cause when the message is persistent and the system remains powered.

• ✗

  Motherboard charging circuit

  Why it's wrong here

  The motherboard's charging circuit consists of power stages, MOSFETs, and a dedicated charger controller; if this circuitry were entirely dead, the laptop would likely fail to boot or run on AC only, because the same rail often powers the system and the battery charger. A partial failure could theoretically cause 'not charging', but that is rare, and diagnosing it first is irresponsible without eliminating the battery and adapter variables. Charging circuit failures also typically require a main-board replacement, so this is an unlikely and costly initial explanation for this specific message.

• ✗

  Power management IC

  Why it's wrong here

  The power management IC (PMIC) regulates voltage conversion and battery charging logic internally, but the fault here is that the AC adapter outputs correct voltage yet the battery does not charge. This points to a broken physical connection path—most likely the DC jack or internal wiring—rather than a failure in the PMIC’s control circuitry. It is tempting because the PMIC directly governs charging behaviour, and if the battery were not detected or the charging circuit were non-responsive, a faulty PMIC would be the correct diagnosis.

Go deeper

Related to this question