問66
頻出度★☆☆
IoT機器やスマートフォンなどに内蔵されているバッテリの容量の表記において, “100mAh” の意味として, 適切なものはどれか。
令和4年度 ITパスポート試験 問66
This question's explanation and your answers so far.
解説
問 66
- ア
正解 mAh (milliampere-hour) is a unit of battery capacity (the amount of electric charge that can be stored), expressed as “current (mA) × time (h)”. Therefore 100mAh means a capacity that can supply a current of 100mA continuously for 1 hour (1h). Choice ア, “It can discharge a current of 100mA for 1 hour”, is exactly this definition, so it is correct. It is also worth remembering that, for the same capacity, halving the current to 50mA lets it last about 2 hours while doubling it to 200mA lasts about 30 minutes — the current and the discharge time are inversely proportional as the charge is used up.
Incorrectイ
mAh is a unit that expresses capacity (electric charge) and has nothing to do with the time required to charge. The phrase “after charging for 100 minutes” is not part of the definition of capacity; the “100” in 100mAh is a current value (mA), not a charging time (minutes).
Incorrectウ
Discharging 1A (=1000mA) for 100 minutes (≒1.67 hours) gives 1000mA × 1.67h ≒ 1667mAh, which is vastly different from 100mAh. The capacity is off by more than an order of magnitude, so it is wrong.
Incorrectエ
It uses charging time as the basis, as in “after charging for 1 hour”, which misinterprets the meaning of the capacity unit mAh. mAh expresses the amount of electric charge that can be discharged, not a value that specifies charging time.
ここがポイント
- mAh (milliampere-hour) is a unit of battery capacity (electric charge) expressed as “current × time”; X mAh means a capacity that can supply X mA for 1 hour.
- For the same capacity, discharge current and discharge time are inversely proportional (raising the current shortens the usable time).
用語