What is the formula used to calculate electrical power (P) in a DC circuit?
The correct answer is A: P = I × E. The formula for calculating electrical power (P) in a DC circuit is P = I × E, where P is power in watts, I is current in amperes, and E is voltage in volts.
This is one of the fundamental electrical formulas, often called the 'power formula.' Power equals current times voltage. For example, if you have 12 volts and 10 amperes, power = 12 × 10 = 120 watts. This formula is essential for calculating power consumption, sizing power supplies, and understanding electrical circuits. It's one of the most important formulas to memorize for amateur radio.
Exam Tip
DC power formula = P = I × E. Remember: Power in watts equals current in amperes times voltage in volts. This is the fundamental power formula.
Memory Aid
"**P**ower = **I** × **E** (think 'PIE' = Power = I × E, or 'P = I times E')"
Real-World Application
Your transceiver operates at 13.8 volts and draws 10 amperes when transmitting. Using the formula P = I × E: Power = 10 A × 13.8 V = 138 watts. This tells you the transceiver is consuming 138 watts of electrical power. This formula is essential for understanding power requirements and sizing power supplies.
FCC Part 97.313Key Concepts
Why Other Options Are Wrong
Option B: Incorrect. P = E / I would give you resistance (R = E / I), not power. Power is current times voltage, not voltage divided by current.
Option C: Incorrect. P = E - I doesn't make sense mathematically. You can't subtract current from voltage to get power.
Option D: Incorrect. P = I + E doesn't make sense mathematically. You can't add current and voltage to get power.
题目解析
The correct answer is A: P = I × E. The formula for calculating electrical power (P) in a DC circuit is P = I × E, where P is power in watts, I is current in amperes, and E is voltage in volts. This is one of the fundamental electrical formulas, often called the 'power formula.' Power equals current times voltage. For example, if you have 12 volts and 10 amperes, power = 12 × 10 = 120 watts. This formula is essential for calculating power consumption, sizing power supplies, and understanding electrical circuits. It's one of the most important formulas to memorize for amateur radio.
考试技巧
DC power formula = P = I × E. Remember: Power in watts equals current in amperes times voltage in volts. This is the fundamental power formula.
记忆口诀
**P**ower = **I** × **E** (think 'PIE' = Power = I × E, or 'P = I times E')
实际应用示例
Your transceiver operates at 13.8 volts and draws 10 amperes when transmitting. Using the formula P = I × E: Power = 10 A × 13.8 V = 138 watts. This tells you the transceiver is consuming 138 watts of electrical power. This formula is essential for understanding power requirements and sizing power supplies.
错误选项分析
Option B: Incorrect. P = E / I would give you resistance (R = E / I), not power. Power is current times voltage, not voltage divided by current. Option C: Incorrect. P = E - I doesn't make sense mathematically. You can't subtract current from voltage to get power. Option D: Incorrect. P = I + E doesn't make sense mathematically. You can't add current and voltage to get power.
知识点
Power formula, P = I × E, DC circuits, Electrical calculations
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.