FAA Aviation Mechanic General (AMG)Fundamentals of Electricity and ElectronicsMedium
A 24-volt aircraft battery is rated at 40 ampere-hours. If a continuous electrical load draws 8 amps, theoretically how long can the battery supply this load before it is fully discharged?
- A8 hours
- B5 hours
- C2 hours
- D320 hours
Show answer & explanationAnswer & explanation
Correct answer: B. 5 hours
Battery capacity in ampere-hours divided by the load current in amps gives the theoretical discharge time. Calculation: 40 Ah / 8 A = 5 hours.
Why the other options are wrong
- A. This confuses the load current with the resulting time value.
- C. This would result from dividing incorrectly or using a lower capacity value.
- D. This results from multiplying instead of dividing capacity by current.
Battery Ampere-Hour Rating
Ampere-hour (Ah) rating indicates how much current a battery can theoretically supply over time; time = Ah rating divided by load current.
- Ah = Amps x Hours
- Time (hours) = Ah rating / load current
- Actual discharge time is affected by temperature and discharge rate
Memory trick: 'Ah divided by Amps gives Hours' - simple division for runtime.