Magnetic field of charge moving at constant velocity

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SUMMARY

The magnetic field generated by a single charge moving at a constant velocity can be calculated using the Biot-Savart law, which states that moving charges create magnetic fields. In a non-relativistic framework, the magnetic field is determined by the charge's velocity and the distance from the charge, following the relationship B = Q V x R / (4πr³). The discussion highlights the significance of Lorentz transformations over Galilean transformations in electromagnetic theory, emphasizing that Maxwell's equations, while originally formulated in a relativistic context, can be adapted to describe the behavior of moving charges in a non-relativistic manner. The Lienard-Wiechert potentials provide a comprehensive solution for the electromagnetic fields of moving charges.

PREREQUISITES
  • Understanding of Maxwell's equations and their implications in electromagnetism.
  • Familiarity with the Biot-Savart law for calculating magnetic fields.
  • Knowledge of Lorentz transformations and their application in physics.
  • Basic concepts of electric and magnetic fields, including Coulomb's law.
NEXT STEPS
  • Study the derivation and applications of the Lienard-Wiechert potentials.
  • Explore the implications of Lorentz invariance in electromagnetic theory.
  • Investigate the differences between static and dynamic electromagnetic fields.
  • Learn about the historical context and development of Maxwell's equations.
USEFUL FOR

Physicists, electrical engineers, and students studying electromagnetism, particularly those interested in the behavior of moving charges and the foundational principles of electromagnetic theory.

  • #31
vanhees71 said:
In the case of a uniformly moving charge you get the fields also from Lorentz boosting the Coulomb field for the charge at rest.

Per Oni said:
Sorry to be a bore about this point, but can anybody demonstrate that?

See here:

http://farside.ph.utexas.edu/teaching/em/lectures/node125.html

(two methods, take your choice)
 
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  • #32
Jtbell that paper your referring to doesn’t look like “ a Lorentz boosted coulomb field” to me. It looks a lot more complicated including a lot of maths and Greek. Oh well, someday someone will come up with something a bit more consumer friendly.
 
  • #33
I find the manuscript by Fitzpatrick excellent. It's also awailable as a textbook. I can only recommend to read his chapter on the fully relativistic treatment of electromagnetics. I never understood, why there is no textbook on classical electromagnetism that from the very beginning strictly uses the relativistic framework. Instead all authors copy more or less the classical textbooks of the first half of the 20th century (although there are excellent books among them, first of all Sommerfeld's Lectures on Theoretical Physics and Becker's book). The only exception is Landau-Lifgarbages in his vol. II, but in vol. VIII he treats the constitutive equations non-relativistic as usual. But that lamento becomes off-topic now...
 
  • #34
Per Oni said:
Jtbell that paper your referring to doesn’t look like “ a Lorentz boosted coulomb field” to me.
But that is exactly what it is.
 
  • #35
Thank you all for the comments and feedback it was most helpful and has spurred me on to do some of the maths for myself. One of my difficulties is that many textbooks "fudge" the solution by ignoring the fact that a point charge is essentially a delta distribution and they skip essential steps in the calculation. However, you all encouraged me to make the effort, after 40 years of abstinence. Thanks!
 

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