Which of the following is combined with an inductor to make a resonant circuit?
The correct answer is Capacitor. A capacitor combined with an inductor makes a resonant circuit (also called a tuned circuit). When an inductor and capacitor are connected together (in series or parallel), they create a circuit that resonates at a specific frequency determined by the values of L and C. This resonance creates a frequency-selective response, making resonant circuits essential for tuning, filtering, and frequency selection. For amateur radio operators, LC resonant circuits are fundamental to antenna tuners, RF filters, oscillators, and receiver tuning. The resonant frequency is calculated as f = 1/(2π√LC), making it a key concept in RF circuit design.
Exam Tip
Capacitor + Inductor = resonant circuit. Think 'L'C circuit = 'L'ooks 'C'ool at one frequency. Resistors add loss, Zener diodes regulate voltage, potentiometers adjust - none create resonance with inductors.
Memory Aid
"Capacitor + Inductor = resonant circuit. Think 'C'apacitor + 'I'nductor = 'C'ircuit that 'I's resonant. LC combination creates frequency-selective resonance."
Real-World Application
In your antenna tuner, an inductor and capacitor form a resonant circuit that matches your antenna's impedance at the operating frequency. By adjusting the capacitor (or inductor), you change the resonant frequency to match your desired band. This LC combination creates the frequency-selective response needed for tuning. The resonance allows maximum power transfer at the tuned frequency.
Key Concepts
Why Other Options Are Wrong
Option A (Resistor): Incorrect. Resistors don't create resonance with inductors. Resistors add loss and damping to circuits but don't form resonant circuits. LC (inductor-capacitor) combinations create resonance.
Option B (Zener diode): Incorrect. Zener diodes are used for voltage regulation, not for creating resonance. They don't combine with inductors to make resonant circuits.
Option C (Potentiometer): Incorrect. Potentiometers are variable resistors used for adjustment, not for resonance. They don't create resonant circuits with inductors.
题目解析
The correct answer is Capacitor. A capacitor combined with an inductor makes a resonant circuit (also called a tuned circuit). When an inductor and capacitor are connected together (in series or parallel), they create a circuit that resonates at a specific frequency determined by the values of L and C. This resonance creates a frequency-selective response, making resonant circuits essential for tuning, filtering, and frequency selection. For amateur radio operators, LC resonant circuits are fundamental to antenna tuners, RF filters, oscillators, and receiver tuning. The resonant frequency is calculated as f = 1/(2π√LC), making it a key concept in RF circuit design.
考试技巧
Capacitor + Inductor = resonant circuit. Think 'L'C circuit = 'L'ooks 'C'ool at one frequency. Resistors add loss, Zener diodes regulate voltage, potentiometers adjust - none create resonance with inductors.
记忆口诀
Capacitor + Inductor = resonant circuit. Think 'C'apacitor + 'I'nductor = 'C'ircuit that 'I's resonant. LC combination creates frequency-selective resonance.
实际应用示例
In your antenna tuner, an inductor and capacitor form a resonant circuit that matches your antenna's impedance at the operating frequency. By adjusting the capacitor (or inductor), you change the resonant frequency to match your desired band. This LC combination creates the frequency-selective response needed for tuning. The resonance allows maximum power transfer at the tuned frequency.
错误选项分析
Option A (Resistor): Incorrect. Resistors don't create resonance with inductors. Resistors add loss and damping to circuits but don't form resonant circuits. LC (inductor-capacitor) combinations create resonance. Option B (Zener diode): Incorrect. Zener diodes are used for voltage regulation, not for creating resonance. They don't combine with inductors to make resonant circuits. Option C (Potentiometer): Incorrect. Potentiometers are variable resistors used for adjustment, not for resonance. They don't create resonant circuits with inductors.
知识点
Resonant circuits, LC circuits, Inductor-capacitor combinations, Tuned circuits
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.