Electromagnetic Waves: Static Charges & Relativity Predictions

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SUMMARY

This discussion focuses on the relationship between static and moving charges and their electromagnetic fields, particularly in the context of relativity. It confirms that static charges exert a radial force described by the formula q1q2/r^2, which can theoretically extend indefinitely in a given frame of reference. The conversation highlights that while electromagnetic waves are produced by accelerating charges, predicting these waves requires a thorough understanding of Maxwell's equations. The historical context reveals that Einstein's theory of relativity emerged from classical electromagnetism challenges.

PREREQUISITES
  • Understanding of electric fields and forces, specifically the formula q1q2/r^2
  • Familiarity with Maxwell's equations and their implications for electromagnetic radiation
  • Basic knowledge of relativity and its historical development in physics
  • Concept of electromagnetic waves and their generation from accelerating charges
NEXT STEPS
  • Study Maxwell's equations in detail to understand electromagnetic wave propagation
  • Explore the principles of electromagnetic radiation as outlined in Purcell's undergraduate textbook
  • Investigate the implications of relativity on classical electromagnetism
  • Research the historical context of Einstein's contributions to electromagnetism and relativity
USEFUL FOR

Physics students, educators, and researchers interested in the interplay between electromagnetism and relativity, as well as those seeking to deepen their understanding of electromagnetic wave generation and behavior.

Fibo112
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I have learned about the electric fields of static charges and those of moving charges. From what I gather(although I have not really learned the specifics) when charges are accelerated they emit electromagntic waves which are essentialy an electromagnetic field progagating through space.

My question is the following: Based on the rules I have learned it seems that if a charge is static in a frame of reference, then its field in that frame of reference will extend out indefinetly. So to someone in that frame, the charge will seem to exert the regular q1q2/r^2 radial force on other charges even if they are millions of light years away?

If yes then at the point in time when the person in the reference frame looks at the distant object and observes the radial force, the distant object has no knowledge of the electrons previous locations in the past x years(x beeing the distance in light years). Can one predict the electromagnetic waves produced by accelerating charges by using relativity arguments based on this?( And also predict the field of moving charges and the same with the magnetic field through similar arguments)
 
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Fibo112 said:
Can one predict the electromagnetic waves produced by accelerating charges by using relativity arguments based on this?
Predict the waves emanating from the distant object, or from the static frame?
 
Fibo112 said:
the charge will seem to exert the regular q1q2/r^2 radial force on other charges even if they are millions of light years away?
Yes, in principle. In practice, the ##1/r^2## factor means that any great distance the field becomes much too small to detect.
Can one predict the electromagnetic waves produced by accelerating charges by using relativity arguments based on this?( And also predict the field of moving charges and the same with the magnetic field through similar arguments)
That line of thought is used in at least one undergraduate textbook (Purcell) to explain the origin of electromagnetic radiation. You have to consider the magnetic field together with the electric field and work through Maxwell's equations to get a complete (as opposed to hand-waving heuristic) explanation, but this is a reasonable start.

No relativity is needed, and in fact the history goes the other way: Einstein started with an open problem in classical electromagnetism to arrive at relativity - he introduced relativity in a paper entitled "On the electrodynamics of moving bodies".
 

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