How can you determine the length of time that equipment can be powered from a battery?
The correct answer is B: Divide the battery ampere-hour rating by the average current draw of the equipment. To determine how long equipment can be powered from a battery, divide the battery's ampere-hour (Ah) rating by the average current draw of the equipment. This gives you the operating time in hours.
Battery capacity is rated in ampere-hours (Ah), which represents how many amperes the battery can supply for one hour (or proportionally for other time periods). If a battery is rated at 10 Ah, it can supply 10 amperes for 1 hour, 5 amperes for 2 hours, 1 ampere for 10 hours, etc. By dividing the Ah rating by your equipment's current draw, you get the operating time. For example, a 10 Ah battery powering equipment drawing 2 amperes will last 10 / 2 = 5 hours.
Exam Tip
Battery operating time = Ah / current. Remember: To find operating time, divide the battery's ampere-hour rating by the average current draw. Time (hours) = Ah / Amperes.
Memory Aid
"**B**attery **T**ime = **A**h / **A**mperes (think 'BT = A/A' = Battery Time = Ah divided by Amperes)"
Real-World Application
You have a 12-volt battery rated at 20 ampere-hours. Your transceiver draws an average of 2 amperes when receiving and 10 amperes when transmitting. If you're transmitting 20% of the time, average current is about 3.6 amperes. Operating time = 20 Ah / 3.6 A = 5.6 hours. This tells you how long you can operate before the battery is depleted.
FCC Part 97.3Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Dividing watt-hours by peak power doesn't account for average power consumption over time. You need to use ampere-hours and average current.
Option C: Incorrect. Multiplying watts per hour by power rating doesn't work. 'Watts per hour' isn't a standard unit, and the calculation method is wrong.
Option D: Incorrect. Multiplying current squared by resistance gives power, not operating time. This doesn't relate to battery capacity.
题目解析
The correct answer is B: Divide the battery ampere-hour rating by the average current draw of the equipment. To determine how long equipment can be powered from a battery, divide the battery's ampere-hour (Ah) rating by the average current draw of the equipment. This gives you the operating time in hours. Battery capacity is rated in ampere-hours (Ah), which represents how many amperes the battery can supply for one hour (or proportionally for other time periods). If a battery is rated at 10 Ah, it can supply 10 amperes for 1 hour, 5 amperes for 2 hours, 1 ampere for 10 hours, etc. By dividing the Ah rating by your equipment's current draw, you get the operating time. For example, a 10 Ah battery powering equipment drawing 2 amperes will last 10 / 2 = 5 hours.
考试技巧
Battery operating time = Ah / current. Remember: To find operating time, divide the battery's ampere-hour rating by the average current draw. Time (hours) = Ah / Amperes.
记忆口诀
**B**attery **T**ime = **A**h / **A**mperes (think 'BT = A/A' = Battery Time = Ah divided by Amperes)
实际应用示例
You have a 12-volt battery rated at 20 ampere-hours. Your transceiver draws an average of 2 amperes when receiving and 10 amperes when transmitting. If you're transmitting 20% of the time, average current is about 3.6 amperes. Operating time = 20 Ah / 3.6 A = 5.6 hours. This tells you how long you can operate before the battery is depleted.
错误选项分析
Option A: Incorrect. Dividing watt-hours by peak power doesn't account for average power consumption over time. You need to use ampere-hours and average current. Option C: Incorrect. Multiplying watts per hour by power rating doesn't work. 'Watts per hour' isn't a standard unit, and the calculation method is wrong. Option D: Incorrect. Multiplying current squared by resistance gives power, not operating time. This doesn't relate to battery capacity.
知识点
Battery capacity, Ampere-hours, Operating time, Current draw
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.