Deep Dive: G5C03
The correct answer is A: 5.9 ohms. The total resistance of 10-, 20-, and 50-ohm resistors connected in parallel is 5.9 ohms. 1/Rtotal = 1/10 + 1/20 + 1/50 = 0.1 + 0.05 + 0.02 = 0.17. Rtotal = 1/0.17 = 5.88Ω ≈ 5.9Ω. For amateur radio operators, this is a basic parallel resistance calculation. Understanding this helps when analyzing parallel circuits.
Why Other Answers Are Wrong
Option B (0.17 ohms): Incorrect. 0.17 ohms is the reciprocal (1/Rtotal), not the total resistance. You need to take 1/0.17 = 5.9Ω. Option C (17 ohms): Incorrect. 17 ohms is too high - parallel resistance is less than the smallest resistor (10Ω). Calculation error. Option D (80 ohms): Incorrect. 80 ohms is the sum (series), not parallel. Parallel resistance is less than the smallest resistor.
Exam Tip
Parallel resistance: 1/R = 1/10 + 1/20 + 1/50 = 0.17, R = 1/0.17 = 5.9Ω. Think 'P'arallel 'R'esistance = 'P'reciprocal sum, then 'R'eciprocal. Use 1/Rtotal = 1/R1 + 1/R2 + 1/R3. Not 0.17Ω (reciprocal), not 17Ω, not 80Ω (sum) - just 5.9Ω.
Memory Aid
Parallel resistance: 1/R = 1/10 + 1/20 + 1/50 = 0.17, R = 5.9Ω. Think 'P'arallel 'R'esistance = 'P'reciprocal sum. Use 1/Rtotal = 1/R1 + 1/R2 + 1/R3, then take reciprocal. Standard parallel calculation.
Real-World Example
Three resistors in parallel: 10Ω, 20Ω, and 50Ω. 1/Rtotal = 1/10 + 1/20 + 1/50 = 0.1 + 0.05 + 0.02 = 0.17. Rtotal = 1/0.17 = 5.88 ohms ≈ 5.9 ohms. Parallel resistance is less than the smallest resistor (10Ω).
Source & Coverage
Question Pool: 2023-2027 Question Pool
Subelement: G5C
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 G5C topic.