IPA IP 2022 Question 66
A question IPA Japan published in 令和4年度 ITパスポート試験 公開問題 問66, translated into English. ITPEC is based on the same exams.
Same question on ITPEC: Apr 2026 Q16 +1 more
In the specification of the capacity of a battery that is embedded in a device such as an IoT device or a smartphone, which of the following is the appropriate meaning of “100mAh”?
Explanation
It can discharge a current of 100mA for one hour — mAh (milliampere-hour) is current multiplied by time.
The capacity is the current the battery can supply times how long it can supply it: 100 × 1 = 100 mAh for 100 mA over one hour. Ideally the same battery gives 50 mA for two hours or 200 mA for half an hour. A device that draws 20 mA runs about 100 ÷ 20 = 5 hours. The unit says nothing about charging, which depends on the charger's current.
Answer (a)
Why not others:
- •(b) and (d) — read the rating as a charging time; mAh measures the charge stored, not how long it takes to charge
- •(c) — 1 A is 1,000 mA and 100 minutes is about 1.67 hours, so 1000 × 1.67 ≈ 1667 mAh, about 17 times the rating; it takes the 100 as minutes and the milli away
Key rule: Dividing a battery's capacity in mAh by the device's current in mA gives its running time in hours.
Hardware · AI-written, may contain errors
This question comes from the past questions IPA Japan publishes, translated into English by ITPEC Practice. ITPEC Practice is an independent study tool and is not affiliated with IPA or ITPEC. See the original paper (PDF) or Report an issue.