What occurs in an LC circuit at resonance?
The correct answer is D: Inductive reactance and capacitive reactance cancel. What occurs in an LC circuit at resonance is that inductive reactance and capacitive reactance cancel. At resonance, XL = XC, so they cancel each other, leaving only resistance. For amateur radio operators, this is the key characteristic of resonance. Understanding this helps when working with resonant circuits.
Exam Tip
LC circuit at resonance = inductive and capacitive reactance cancel. Think 'L'C 'R'esonance = 'L' and 'C' 'R'eactances cancel. At resonance, XL = XC, so they cancel, leaving only resistance. Not current/voltage equality, not resistance cancellation, not radiation - just reactance cancellation.
Memory Aid
"LC circuit at resonance = inductive and capacitive reactance cancel. Think 'L'C 'R'esonance = 'L' and 'C' 'R'eactances cancel. At resonance, XL = XC, so they cancel, leaving only resistance. Key characteristic of resonance."
Real-World Application
An LC circuit at resonance: Inductive reactance (XL) equals capacitive reactance (XC), so they cancel each other. Only the circuit resistance remains, so impedance is minimum (just resistance). This reactance cancellation is what defines resonance in LC circuits.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Current and voltage aren't equal at resonance - they're related by impedance, but equality isn't the characteristic. Reactance cancellation is the key.
Option B: Incorrect. Resistance isn't cancelled - resistance remains. Only reactances cancel, not resistance.
Option C: Incorrect. The circuit doesn't radiate all energy as radio waves - that's not what happens at resonance. Reactance cancellation is the key, not radiation.
题目解析
The correct answer is D: Inductive reactance and capacitive reactance cancel. What occurs in an LC circuit at resonance is that inductive reactance and capacitive reactance cancel. At resonance, XL = XC, so they cancel each other, leaving only resistance. For amateur radio operators, this is the key characteristic of resonance. Understanding this helps when working with resonant circuits.
考试技巧
LC circuit at resonance = inductive and capacitive reactance cancel. Think 'L'C 'R'esonance = 'L' and 'C' 'R'eactances cancel. At resonance, XL = XC, so they cancel, leaving only resistance. Not current/voltage equality, not resistance cancellation, not radiation - just reactance cancellation.
记忆口诀
LC circuit at resonance = inductive and capacitive reactance cancel. Think 'L'C 'R'esonance = 'L' and 'C' 'R'eactances cancel. At resonance, XL = XC, so they cancel, leaving only resistance. Key characteristic of resonance.
实际应用示例
An LC circuit at resonance: Inductive reactance (XL) equals capacitive reactance (XC), so they cancel each other. Only the circuit resistance remains, so impedance is minimum (just resistance). This reactance cancellation is what defines resonance in LC circuits.
错误选项分析
Option A: Incorrect. Current and voltage aren't equal at resonance - they're related by impedance, but equality isn't the characteristic. Reactance cancellation is the key. Option B: Incorrect. Resistance isn't cancelled - resistance remains. Only reactances cancel, not resistance. Option C: Incorrect. The circuit doesn't radiate all energy as radio waves - that's not what happens at resonance. Reactance cancellation is the key, not radiation.
知识点
LC circuit, Resonance, Reactance cancellation, XL and XC cancel
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.