Why does DC current not generate EMR?

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Discussion Overview

The discussion centers on the question of why direct current (DC) does not generate electromagnetic radiation (EMR) despite the acceleration of electrons during current flow. Participants explore the relationship between electron motion, heat generation, and electromagnetic radiation, touching on both theoretical and conceptual aspects.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants note that electrons are accelerated and decelerated between collisions with the metal lattice, raising the question of why this does not lead to EMR in a DC current.
  • One participant mentions that the drift speed of electrons is very slow compared to their random thermal motion, suggesting that this slow drift speed does not contribute significantly to the acceleration needed for EMR.
  • Another participant argues that while the accelerations of electrons can cause electromagnetic radiation, this radiation is dependent on temperature rather than the presence of current, with infrared radiation being emitted as the material heats up.
  • Some participants assert that heat is a byproduct of passing DC voltage through a wire, although there is contention regarding the classification of heat as a form of electromagnetic radiation.
  • One participant clarifies that heat is not electromagnetic radiation but rather the random motion of particles, while noting that EM radiation can convert to heat upon absorption.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between heat, electron motion, and electromagnetic radiation. There is no consensus on whether heat can be classified as a form of electromagnetic radiation, and the discussion remains unresolved regarding the mechanisms by which DC current interacts with EMR.

Contextual Notes

There are limitations in the discussion regarding the definitions of heat and electromagnetic radiation, as well as the assumptions about electron motion and its contributions to radiation. The scope of the discussion does not fully address the complexities of these interactions.

suhasm
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During current flow , electrons are certainly being accelerated and decelerated betweeen two successive collisions with the metal lattice. Since accelerated charge generates EM waves , why doesn't a DC current emit EMR?
 
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heat is a form of magnetic radiation

Pass DC voltage thru a wire and heat is the byproduct
 
suhasm said:
During current flow , electrons are certainly being accelerated and decelerated betweeen two successive collisions with the metal lattice. Since accelerated charge generates EM waves , why doesn't a DC current emit EMR?

The drift speed of electrons is incredibly slow compared to the random motions of the electrons. The drift speed is less than a millimeter per second, compared to hundreds of meters per second, for the so the drift speed will make no measurable contribution to the accelerations of the electrons.

The accelerations of electrons will always cause electromagnetic radiation, and this depends only on the temperature and not on the the presence of current. Until the material becomes so hot it starts to glow, the radiation will be infrared radiation.

Of course, the current can heat up the material, that will then radiate more infrared.
 
mkillman said:
heat is a form of magnetic radiation

Pass DC voltage thru a wire and heat is the byproduct

Heat is not a form of EM radiation. It is the random motion of particles in a material. EM radiation can be converted to heat upon being absorbed though.
 

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