Deep Dive: G5A12
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.
Why Other Answers 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.
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 Example
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.
Source & Coverage
Question Pool: 2023-2027 Question Pool
Subelement: G5A
Reference: 2023-2027 Question Pool · G5 - Electrical Principles
Key Concepts
Verified Content
Question from the official FCC General Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the G5A topic.