Deep Dive: E5B09
The correct answer is D: Current leads voltage by 90 degrees. What is the relationship between the AC current through a capacitor and the voltage across a capacitor is that current leads voltage by 90 degrees. In a capacitor, current leads voltage by 90°. For amateur radio operators, this is important for circuit theory. Understanding this helps when working with capacitors.
Why Other Answers Are Wrong
Option A: Incorrect. Voltage and current in phase isn't correct - in a capacitor, current leads voltage by 90°. In phase is wrong. Option B: Incorrect. Voltage and current 180 degrees out of phase isn't correct - in a capacitor, current leads voltage by 90°. 180° is wrong. Option C: Incorrect. Voltage leads current by 90 degrees isn't correct - in a capacitor, current leads voltage by 90°. Voltage leading is wrong.
Exam Tip
Capacitor AC relationship = current leads voltage by 90 degrees. Think 'C'apacitor = 'C'urrent 'L'eads. In a capacitor, current leads voltage by 90°. Not in phase, not 180°, not voltage leading - just current leads by 90°.
Memory Aid
Capacitor AC relationship = current leads voltage by 90 degrees. Think 'C'apacitor = 'C'urrent 'L'eads. In a capacitor, current leads voltage by 90°. Important for circuit theory.
Real-World Example
AC current through a capacitor and voltage across a capacitor: The current leads the voltage by 90 degrees. This is because the capacitor's current responds immediately to voltage changes, while the voltage builds up. This is the relationship - current leads voltage by 90°.
Source & Coverage
Question Pool: 2024-2028 Question Pool
Subelement: E5B
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 E5B topic.