Deep Dive: E5D11
The correct answer is B: 100 watts. How much real power is consumed in a circuit consisting of a 100-ohm resistor in series with a 100-ohm inductive reactance drawing 1 ampere is 100 watts. Real power = I²R = 1² × 100 = 100 watts. Only resistance consumes real power. For amateur radio operators, this is important for power calculations. Understanding this helps when calculating power.
Why Other Answers Are Wrong
Option A (70.7 watts): Incorrect. 70.7 watts is too low - real power = I²R = 1² × 100 = 100 watts. 70.7 watts is wrong. Option C (141.4 watts): Incorrect. 141.4 watts is too high - real power = I²R = 1² × 100 = 100 watts. 141.4 watts is wrong. Option D (200 watts): Incorrect. 200 watts is too high - real power = I²R = 1² × 100 = 100 watts. 200 watts is wrong.
Exam Tip
Real power = I²R (only resistance consumes real power). Think 'R'eal 'P'ower = 'I'²'R'. Real power = 1² × 100 = 100 watts. Not 70.7W, not 141.4W, not 200W - just 100 watts.
Memory Aid
Real power = I²R (only resistance consumes real power). Think 'R'eal 'P'ower = '1'00 watts. Real power = 1² × 100 = 100 watts. Important for power calculations.
Real-World Example
A circuit with 100-ohm resistor and 100-ohm inductive reactance drawing 1 ampere: Real power = I²R = 1² × 100 = 100 watts. Only the resistance consumes real power; the reactance doesn't. This is the real power - 100 watts.
Source & Coverage
Question Pool: 2024-2028 Question Pool
Subelement: E5D
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 E5D topic.