Deep Dive: E5A02
The correct answer is C: 3.56 MHz. What is the resonant frequency of an RLC circuit if R is 22 ohms, L is 50 microhenries, and C is 40 picofarads is 3.56 MHz. f = 1/(2π√(LC)) = 1/(2π√(50×10^-6 × 40×10^-12)) ≈ 3.56 MHz. For amateur radio operators, this is important for circuit calculations. Understanding this helps when designing resonant circuits.
Why Other Answers Are Wrong
Option A (44.72 MHz): Incorrect. 44.72 MHz is too high - the calculation gives 3.56 MHz. 44.72 MHz is wrong. Option B (22.36 MHz): Incorrect. 22.36 MHz is too high - the calculation gives 3.56 MHz. 22.36 MHz is wrong. Option D (1.78 MHz): Incorrect. 1.78 MHz is too low - the calculation gives 3.56 MHz. 1.78 MHz is wrong.
Exam Tip
RLC resonant frequency = 1/(2π√(LC)). Think 'R'esonant 'F'requency = '1'/(2π√('L'C)). f = 1/(2π√(50×10^-6 × 40×10^-12)) ≈ 3.56 MHz. Not 44.72 MHz, not 22.36 MHz, not 1.78 MHz - just 3.56 MHz.
Memory Aid
RLC resonant frequency = 1/(2π√(LC)). Think 'R'esonant = '1'/(2π√('L'C)). f = 1/(2π√(50×10^-6 × 40×10^-12)) ≈ 3.56 MHz. Important for circuit calculations.
Real-World Example
An RLC circuit with R=22 ohms, L=50 microhenries, C=40 picofarads: The resonant frequency is f = 1/(2π√(LC)) = 1/(2π√(50×10^-6 × 40×10^-12)) ≈ 3.56 MHz. Note that R doesn't affect resonant frequency. This is the frequency - 3.56 MHz.
Source & Coverage
Question Pool: 2024-2028 Question Pool
Subelement: E5A
Reference: 2024-2028 Question Pool · E5 - Electrical Principles
Key Concepts
Verified Content
Question from the official FCC Extra Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the E5A topic.