What happens when an inductor is operated above its self-resonant frequency?
The correct answer is C: It becomes capacitive. What happens when an inductor is operated above its self-resonant frequency is that it becomes capacitive. Above self-resonance, the inductor's parasitic capacitance dominates, making it behave like a capacitor. For amateur radio operators, this is important for RF circuit design. Understanding this helps when using inductors at high frequencies.
Exam Tip
Inductor above self-resonance = becomes capacitive. Think 'A'bove 'R'esonance = 'A'cting 'R'everse (capacitive). Above self-resonant frequency, parasitic capacitance dominates, making inductor behave like capacitor. Not increasing reactance, not harmonics, not failure - just becomes capacitive.
Memory Aid
"Inductor above self-resonance = becomes capacitive. Think 'A'bove 'R'esonance = 'A'cting 'R'everse. Above self-resonant frequency, parasitic capacitance dominates, making inductor behave like capacitor. Important for RF design."
Real-World Application
An inductor has a self-resonant frequency of 10 MHz. Below 10 MHz, it behaves as an inductor. Above 10 MHz, the parasitic capacitance dominates, and it behaves like a capacitor. This is why inductors have frequency limits - above self-resonance, they don't work as inductors anymore.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Reactance doesn't continue increasing above self-resonance - above resonance, the inductor becomes capacitive, so reactance decreases. Behavior changes at resonance.
Option B: Incorrect. Harmonics aren't generated by operating above self-resonance - harmonics come from non-linear operation, not from frequency above resonance. Harmonics aren't the issue.
Option D: Incorrect. Catastrophic failure isn't likely - the inductor just behaves differently (capacitively), it doesn't fail. Failure isn't the result.
题目解析
The correct answer is C: It becomes capacitive. What happens when an inductor is operated above its self-resonant frequency is that it becomes capacitive. Above self-resonance, the inductor's parasitic capacitance dominates, making it behave like a capacitor. For amateur radio operators, this is important for RF circuit design. Understanding this helps when using inductors at high frequencies.
考试技巧
Inductor above self-resonance = becomes capacitive. Think 'A'bove 'R'esonance = 'A'cting 'R'everse (capacitive). Above self-resonant frequency, parasitic capacitance dominates, making inductor behave like capacitor. Not increasing reactance, not harmonics, not failure - just becomes capacitive.
记忆口诀
Inductor above self-resonance = becomes capacitive. Think 'A'bove 'R'esonance = 'A'cting 'R'everse. Above self-resonant frequency, parasitic capacitance dominates, making inductor behave like capacitor. Important for RF design.
实际应用示例
An inductor has a self-resonant frequency of 10 MHz. Below 10 MHz, it behaves as an inductor. Above 10 MHz, the parasitic capacitance dominates, and it behaves like a capacitor. This is why inductors have frequency limits - above self-resonance, they don't work as inductors anymore.
错误选项分析
Option A: Incorrect. Reactance doesn't continue increasing above self-resonance - above resonance, the inductor becomes capacitive, so reactance decreases. Behavior changes at resonance. Option B: Incorrect. Harmonics aren't generated by operating above self-resonance - harmonics come from non-linear operation, not from frequency above resonance. Harmonics aren't the issue. Option D: Incorrect. Catastrophic failure isn't likely - the inductor just behaves differently (capacitively), it doesn't fail. Failure isn't the result.
知识点
Inductor, Self-resonant frequency, Capacitive behavior, Parasitic capacitance
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.