Electric field in coaxial cable

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SUMMARY

The discussion centers on the propagation of Transverse Electromagnetic (TEM) waves in coaxial cables, specifically addressing the apparent contradiction between Ohm's Law (J=σE) and the behavior of electric fields in ideal conditions. It is established that within coaxial cables, the electric field (E) is oriented along the axis of the cable, while a perpendicular component exists between the conductors due to surface charges. The conversation highlights the complexities of charge movement in an idealized scenario where the cable exhibits infinite conductivity, leading to a zero longitudinal electric field (Ez=0).

PREREQUISITES
  • Understanding of Transverse Electromagnetic (TEM) wave propagation
  • Familiarity with Ohm's Law (J=σE)
  • Knowledge of electric field behavior in coaxial cables
  • Basic principles of surface charge distribution
NEXT STEPS
  • Study the mathematical derivation of TEM wave propagation in coaxial cables
  • Explore the effects of surface charges on electric fields in conductors
  • Investigate the implications of infinite conductivity in electrical engineering
  • Learn about the characteristics of ideal versus real coaxial cables
USEFUL FOR

Physics students, electrical engineers, and anyone interested in the theoretical aspects of wave propagation in coaxial cables.

oocelik
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Every physics books show that wave prograpation in coxial cable is TEM wave, like in the picture. But we know that J=σ E from ohms law, which says current in same direction with E field, which is not the case here. What do you think the reason is ?

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Hello Dale,

Thank you for the reply. But I am talking about the ideal case where the cable has infinite conductivity and progpagation is pure TEM wave, which makes it sure that there is no "longitudinal" (i.e Ez=0) along the cable by definition. In this case, what force acts on the charges to flow down the cable ?
 

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