Deep Dive: E5B10
The correct answer is A: Voltage leads current by 90 degrees. What is the relationship between the AC current through an inductor and the voltage across an inductor is that voltage leads current by 90 degrees. In an inductor, voltage leads current by 90°. For amateur radio operators, this is important for circuit theory. Understanding this helps when working with inductors.
Why Other Answers Are Wrong
Option B: Incorrect. Current leads voltage by 90 degrees isn't correct - in an inductor, voltage leads current by 90°. Current leading is wrong. Option C: Incorrect. Voltage and current are 180 degrees out of phase isn't correct - in an inductor, voltage leads current by 90°. 180° is wrong. Option D: Incorrect. Voltage and current are in phase isn't correct - in an inductor, voltage leads current by 90°. In phase is wrong.
Exam Tip
Inductor AC relationship = voltage leads current by 90 degrees. Think 'I'nductor = 'V'oltage 'L'eads. In an inductor, voltage leads current by 90°. Not current leading, not 180°, not in phase - just voltage leads by 90°.
Memory Aid
Inductor AC relationship = voltage leads current by 90 degrees. Think 'I'nductor = 'V'oltage 'L'eads. In an inductor, voltage leads current by 90°. Important for circuit theory.
Real-World Example
AC current through an inductor and voltage across an inductor: The voltage leads the current by 90 degrees. This is because the inductor opposes current changes, so voltage appears before current builds up. This is the relationship - voltage leads current 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.