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In a standard coaxial cable construction, the braided copper sheath is primarily used as which layer?

Difficulty: Easy

Correct Answer: Electromagnetic shield (return/ground)

Explanation:


Introduction / Context:
Coaxial cables carry high-frequency signals with minimal radiation and susceptibility to external interference. Their layered construction is designed to confine electromagnetic fields within the dielectric between inner conductor and outer shield.



Given Data / Assumptions:

  • Typical coax: solid/stranded inner conductor; uniform dielectric; braided or foil outer conductor; protective outer jacket.
  • Purpose is efficient RF transmission with controlled impedance (e.g., 50 Ω or 75 Ω).
  • Braided copper provides both electrical and partial mechanical functions.


Concept / Approach:
The braided copper (sometimes with foil) forms the outer conductor connected to ground (return path) and acts as an electromagnetic shield. It prevents external fields from entering and internal fields from radiating out, preserving signal integrity. The dielectric provides spacing and sets the characteristic impedance, while the jacket offers environmental protection.



Step-by-Step Solution:

Identify each layer’s function: inner conductor (signal), dielectric (spacing), braid/foil (shield & return), jacket (protection).Recognize that the braid is not the central conductor or dielectric.Conclude the braid is the shield/return path.


Verification / Alternative check:

Check continuity from braid to connector shells and system ground in RF systems; this confirms its shielding/return role.


Why Other Options Are Wrong:

Central conductor is a separate solid/stranded wire.Dielectric is polymer foam/solid (e.g., PE, PTFE), not the braid.Jacket is typically PVC/PE for protection, not copper.


Common Pitfalls:

Assuming the shield is purely mechanical; it is an electrical conductor that defines the coaxial return path.


Final Answer:

Electromagnetic shield (return/ground)
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