Deep Dive: G5C04
The correct answer is D: 67 ohms. The approximate total resistance of 100- and 200-ohm resistors in parallel is 67 ohms. 1/Rtotal = 1/100 + 1/200 = 0.01 + 0.005 = 0.015. Rtotal = 1/0.015 = 66.7Ω ≈ 67Ω. For amateur radio operators, this is a basic parallel resistance calculation. Understanding this helps when analyzing parallel circuits.
Why Other Answers Are Wrong
Option A (300 ohms): Incorrect. 300 ohms is the sum (series), not parallel. Parallel resistance is less than the smallest resistor (100Ω). Option B (150 ohms): Incorrect. 150 ohms is the average, not the parallel resistance. Parallel resistance is less than the smallest resistor. Option C (75 ohms): Incorrect. 75 ohms is close but not exact - exact is 66.7Ω ≈ 67Ω. Calculation error.
Exam Tip
Parallel resistance: 1/R = 1/100 + 1/200 = 0.015, R = 1/0.015 = 67Ω. Think 'P'arallel 'R'esistance = 'P'reciprocal sum. Use 1/Rtotal = 1/R1 + 1/R2. Not 300Ω (sum), not 150Ω (average), not 75Ω - just 67Ω.
Memory Aid
Parallel resistance: 1/R = 1/100 + 1/200 = 0.015, R = 67Ω. Think 'P'arallel 'R'esistance = 'P'reciprocal sum. Use 1/Rtotal = 1/R1 + 1/R2, then take reciprocal. Approximate 67 ohms.
Real-World Example
Two resistors in parallel: 100Ω and 200Ω. 1/Rtotal = 1/100 + 1/200 = 0.01 + 0.005 = 0.015. Rtotal = 1/0.015 = 66.7 ohms ≈ 67 ohms. Parallel resistance is less than the smallest resistor (100Ω).
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.