How much power is delivered by a voltage of 12 volts DC and a current of 2.5 amperes?
The correct answer is B: 30 watts. With a voltage of 12 volts DC and a current of 2.5 amperes, the power delivered is 30 watts. Using the power formula P = I × E: P = 2.5 A × 12 V = 30 watts.
This is a straightforward application of the power formula. 12 volts is a common battery voltage, and 2.5 amperes is a moderate current draw. The calculation is simple: 2.5 × 12 = 30. This power level might represent a small transceiver or a receiver's power consumption.
Exam Tip
Power = Current × Voltage. Remember: P = I × E. 2.5 A × 12 V = 30 W. Simple multiplication.
Memory Aid
"**2**.**5**A × **1**2V = **3**0W (think '2.5 × 12 = 30')"
Real-World Application
A small receiver operating from a 12-volt battery draws 2.5 amperes. The power consumed is 2.5 × 12 = 30 watts. This tells you the receiver's power consumption, which helps you calculate how long the battery will last and size appropriate power supplies.
FCC Part 97.313Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. 4.8 watts would be the result of dividing (12 / 2.5 = 4.8), not multiplying. Power is I × E, not E / I.
Option C: Incorrect. 14.5 watts would be the result of adding (12 + 2.5 = 14.5), not the correct power calculation.
Option D: Incorrect. 0.208 watts would be the result of dividing (2.5 / 12 = 0.208), not the correct power calculation.
题目解析
The correct answer is B: 30 watts. With a voltage of 12 volts DC and a current of 2.5 amperes, the power delivered is 30 watts. Using the power formula P = I × E: P = 2.5 A × 12 V = 30 watts. This is a straightforward application of the power formula. 12 volts is a common battery voltage, and 2.5 amperes is a moderate current draw. The calculation is simple: 2.5 × 12 = 30. This power level might represent a small transceiver or a receiver's power consumption.
考试技巧
Power = Current × Voltage. Remember: P = I × E. 2.5 A × 12 V = 30 W. Simple multiplication.
记忆口诀
**2**.**5**A × **1**2V = **3**0W (think '2.5 × 12 = 30')
实际应用示例
A small receiver operating from a 12-volt battery draws 2.5 amperes. The power consumed is 2.5 × 12 = 30 watts. This tells you the receiver's power consumption, which helps you calculate how long the battery will last and size appropriate power supplies.
错误选项分析
Option A: Incorrect. 4.8 watts would be the result of dividing (12 / 2.5 = 4.8), not multiplying. Power is I × E, not E / I. Option C: Incorrect. 14.5 watts would be the result of adding (12 + 2.5 = 14.5), not the correct power calculation. Option D: Incorrect. 0.208 watts would be the result of dividing (2.5 / 12 = 0.208), not the correct power calculation.
知识点
Power calculation, P = I × E, DC power, Electrical calculations
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.