Magnetic Force and Frame of Reference

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Discussion Overview

The discussion revolves around the nature of magnetic force and its dependence on the frame of reference, particularly in the context of a charged particle moving perpendicular to a magnetic field. Participants explore the implications of different reference frames, including inertial and non-inertial frames, and how these affect the observation of forces acting on the particle.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant suggests that if an observer moves at the same velocity as a charged particle, they would not observe any magnetic force due to the particle's velocity being zero relative to them, proposing that this scenario involves a non-inertial reference frame.
  • Another participant counters that an observer can always find an inertial frame where the particle is momentarily at rest, indicating that the electromagnetic fields transform under changes of inertial frames, leading to a different interpretation of forces.
  • A third participant argues that magnetic and electric forces are not real forces on their own, but rather part of the electromagnetic force, emphasizing that force is frame independent while velocity is frame dependent.
  • This participant also asserts that the charged particle is moving in an inertial frame since it is moving with a constant velocity, challenging the initial claim about non-inertial frames.

Areas of Agreement / Disagreement

Participants express differing views on the nature of magnetic force and the implications of reference frames. There is no consensus on the correctness of the initial claim regarding non-inertial frames and the observation of forces.

Contextual Notes

Participants have not resolved the implications of frame dependence on the observation of forces, and there are unresolved questions about the definitions and interpretations of inertial versus non-inertial frames in this context.

UncertaintyAjay
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So, a friend asked me this question in school and I've come up with an answer, I'm just not sure that it is right.
Say you have a charged particle moving perpendicular to a magnetic field. There will be a force acting on it given by F=qvB.
Now suppose your'e moving along at the same velocity as said particle. It's velocity respective to you is zero, so you should not observe any magnetic force even though there is one.

My answer is this:
From an inertial frame, the charged particle will be moving in a non-inertial reference frame. So if you move along at the same velocity as the particle, yours is an accelerated reference frame too and you don't observe any force on the particle because of pseudo forces.
Is this right?
 
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No. You can always place yourself in an inertial frame where the particle is momentarily at rest. The solution to your conundrum has nothing to do with accelerated frames. It is based on the fact that the electromagnetic fields transform under changes of inertial frames. What might have been a pure magnetic field in your original frame will be a combination of electric and magnetic fields in the instantaneous rest frame of the particle. What appeared as a magnetic force in your original frame is an electric force in the particle rest frame.
 
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Thanks a lot!
 
No. Magnetic force is not a real force, Neither is electric force. Only sum of magnetic and electric force (electromagnetic force) is a real force. What your friend said was absolutely correct. Force is frame independent and velocity is frame dependent. Then how the hell can we relate these two? It completely violates the rules of inertial frame and non inertial frames.
Also seeing your friends statement, we can conclude that magnetic force is not really a force. And by the way your statement is wrong. The charged particle will move in an inertial frame, as it is moving with a constant velocity.
 
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