What is the significance of velocity in relativistic electromagnetism?

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Discussion Overview

The discussion centers around the significance of velocity in the context of relativistic electromagnetism, particularly in relation to the force experienced by charged particles in magnetic fields. Participants explore the implications of different reference frames on the interpretation of electromagnetic fields.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant questions the reference frame for the velocity v in the equation F=q(v*B), seeking clarification on its significance.
  • Another participant responds that the velocity is with respect to the frame of reference from which the magnetic field B is observed, highlighting the importance of the reference frame.
  • A further contribution emphasizes that the magnetic field is part of the broader electromagnetic field, noting that both electric and magnetic fields must be considered when switching between reference frames. This participant points out that changes in velocity v also affect the electric field E and magnetic field B.
  • One participant recommends Purcell's book on electromagnetism as a valuable resource for understanding these concepts.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the implications of velocity in different reference frames, as the discussion includes multiple perspectives on how electromagnetic fields interact under relativity.

Contextual Notes

The discussion does not resolve the complexities of how electric and magnetic fields transform between reference frames, nor does it clarify the specific conditions under which the initial assumptions about the fields are made.

Criticalsandy
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I have read:
F=q(v*B)

where q=charge of the particle
v=velocity of the charge particle
B=magnetic flux density
F= force experienced by the charged particle

Now,I could not understand what is the velocity v with respect to?

Please help me.
 
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V is with respect to that frame of reference from which you are observing that B.
Remember B field also needs frame of reference.
It was a nice question though. And, BTW, Welcome to P.F.
 
Remember, the magnetic field is only part of the electromagnetic field. In relativity, you cannot escape dealing with the other part (the electric field) also, when switching between different reference frames (points of view):

[tex]\vec F = q (\vec E + \vec v \times \vec B)[/tex]

When you switch from one reference frame to another, not only does v change, but so do E and B. If you start with only a B field in one frame (zero E field), in some other frame (different v) you also have an E field, in general. Likewise if you start out with only an E field in one frame, in another frame you have both an E and a B field.
 
Purcell's book on E&M is fantastic for this sort of thing, I highly recommend it.
 

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