Deep Dive: E4E08
The correct answer is B: Common-mode current. What current flows equally on all conductors of an unshielded multiconductor cable is common-mode current. Common-mode current flows equally on all conductors. For amateur radio operators, this is important for understanding cable currents. Understanding this helps when troubleshooting interference.
Why Other Answers Are Wrong
Option A (Differential-mode current): Incorrect. Differential-mode current doesn't flow equally - it flows in opposite directions on different conductors. Differential-mode isn't equal. Option C (Reactive current only): Incorrect. Reactive current only isn't the answer - common-mode current flows equally. Reactive current isn't the answer. Option D (Magnetically-coupled current only): Incorrect. Magnetically-coupled current only isn't the answer - common-mode current flows equally. Magnetically-coupled isn't the answer.
Exam Tip
Current flowing equally on all conductors = common-mode current. Think 'C'ommon-'M'ode = 'C'urrent on 'M'any conductors equally. Common-mode current flows equally on all conductors. Not differential-mode, not reactive only, not magnetically-coupled only - just common-mode.
Memory Aid
Current flowing equally on all conductors = common-mode current. Think 'C'ommon-'M'ode = 'E'qual on 'A'll. Common-mode current flows equally on all conductors. Important for understanding cable currents.
Real-World Example
An unshielded multiconductor cable: Common-mode current flows equally on all conductors. This is current that flows in the same direction on all conductors, as opposed to differential-mode current which flows in opposite directions. This is the current - common-mode current.
Source & Coverage
Question Pool: 2024-2028 Question Pool
Subelement: E4E
Reference: 2024-2028 Question Pool · E4 - Amateur Practices
Key Concepts
Verified Content
Question from the official FCC Extra Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the E4E topic.