Which transmission line configuration is effectively non-radiating in normal operation?

Introduction / Context:
Transmission lines are intended to guide energy, not radiate it. Line geometry determines field confinement and susceptibility to radiation losses, interference, and EMC issues.

Given Data / Assumptions:

• Coaxial line: inner conductor, dielectric, outer shielding conductor (return), with TEM mode confined between conductors.
• Open two-wire line: parallel conductors exposed to free space, supporting external fields.

Concept / Approach:
Coaxial cables are designed so that the electromagnetic field is almost entirely confined within the dielectric between inner and outer conductors; external radiation is negligible when the cable is properly terminated and shield integrity is maintained. Open two-wire lines, by contrast, have fringing fields in free space and can radiate, especially when unbalanced or near discontinuities.

Step-by-Step Solution:

Verification / Alternative check:
EMC measurements show far less radiated emission from coax than from open two-wire lines for the same guided power, assuming correct terminations and integrity.

Why Other Options Are Wrong:

Common Pitfalls:

Final Answer: