Deep Dive: E5C01
The correct answer is A: 0 - j100. Which of the following represents pure capacitive reactance of 100 ohms in rectangular notation is 0 - j100. Capacitive reactance is negative imaginary (0 - jX). For amateur radio operators, this is important for circuit theory. Understanding this helps when working with impedance notation.
Why Other Answers Are Wrong
Option B (0 + j100): Incorrect. 0 + j100 is inductive reactance, not capacitive - capacitive is negative imaginary. +j100 is inductive. Option C (100 - j0): Incorrect. 100 - j0 is pure resistance, not capacitive reactance - capacitive is negative imaginary. 100 - j0 is resistance. Option D (100 + j0): Incorrect. 100 + j0 is pure resistance, not capacitive reactance - capacitive is negative imaginary. 100 + j0 is resistance.
Exam Tip
Pure capacitive reactance in rectangular = 0 - jX. Think 'C'apacitive = 'C'apacitive reactance is 'N'egative imaginary (0 - jX). Capacitive reactance is negative imaginary (0 - j100). Not +j100 (inductive), not 100±j0 (resistance) - just 0 - j100.
Memory Aid
Pure capacitive reactance in rectangular = 0 - jX. Think 'C'apacitive = 'N'egative imaginary. Capacitive reactance is negative imaginary (0 - j100). Important for circuit theory.
Real-World Example
Pure capacitive reactance of 100 ohms in rectangular notation: It's represented as 0 - j100. The real part is 0 (no resistance), and the imaginary part is -j100 (capacitive reactance is negative). This is the notation - 0 - j100.
Source & Coverage
Question Pool: 2024-2028 Question Pool
Subelement: E5C
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 E5C topic.