Question
What current flows equally on all conductors of an unshielded multiconductor cable?
Answer Options
- A) Differential-mode current
- B) Common-mode current
- C) Reactive current only
- D) Magnetically-coupled current only
Correct Answer: B
Explanation
In an electrical system, current can flow in two primary ways: differential mode or common mode. Differential mode is the desired signal current flowing between two conductors (forward on one, return on the other). Common-mode current, however, is a product of noise and external fields.
Common-mode current is defined as current that flows equally on all conductors of an unshielded multiconductor cable and returns through an external path (often the ground system or the chassis). This unwanted current turns the entire cable assembly into a large antenna, causing both the reception and radiation of Radio Frequency Interference (RFI).
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