My question about the sum of the electrons' magnetic moments in a wire(What is the sum of the electrons' magnetic moments in a wire?) had an answer which disappeared later. The answer was - if I understood right - that were is a moment in sum.

If there is a moment, could this explain the Lorentz force?

  • $\begingroup$ Lorentz force does not describe force on particle/charged body as a function of its magnetic moment, but as a function of its electric charge and velocity. Particle has those and experiences Lorentz force even if it does not have magnetic moment, so explaining Lorentz force with magnetic moment is a very strange idea. $\endgroup$ – Ján Lalinský Sep 6 '14 at 10:50
  • $\begingroup$ @Ján Lalinský: I know it's strange. But it explains why electrons make this "side move". And more, it explains why at this moment the electron radiates and after builds up an contrary field. Magnetic field turns the electrons magnetic moment and, if electron is in movement, it will be accelerated to the side. Acceleration = photon emission. Emission has a impuls and the electron get back. After it starts again so long as the electron is in the magnetic field. It works for all 3 possibilities if you switch the equation $ \vec F = q \vec v \times \vec B $ and also for the Homopolar generator. $\endgroup$ – HolgerFiedler Sep 6 '14 at 14:56
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    $\begingroup$ @JánLalinský: Which particles have no magnetic moment but get a Lorentz force when they move through a magnetic field? $\endgroup$ – HolgerFiedler Sep 7 '14 at 19:25
  • $\begingroup$ Whether particle has or has not magnetic moment is hard to decide experimentally. The approach usually taken is to use only as little parameters as needed to explain given experiment. For description of trajectories of electrons in external electromagnetic field, like in synchrotron or electron microscope, magnetic moment of electron is ignored. In quantum theory electron is ascribed non-zero magnetic moment to explain spectroscopic measurements. $\endgroup$ – Ján Lalinský Sep 8 '14 at 18:40

No. The Lorentz force $$ \vec F = q\left( \vec E + \vec v \times \vec B \right) $$ describes the interaction of a charge with electric and magnetic fields. A magnetic dipole moment is a convenient way to describe the source term for a very common field distribution — there are tons of problems where you compute the magnetic field for a rotating charged sphere and discover it's a dipole. However there's no way that you can start from an arrangement of dipole fields and produce a monopole field. The charge is in some way "more fundamental" than the magnetic moment.

  • $\begingroup$ The question was about the reason for the acceleration of moving particles in magnetic fields. In the way, why uncharged particles are not feel the Lorentz force. I'll take it into a separate question. $\endgroup$ – HolgerFiedler Sep 7 '14 at 19:38

The electromagnetic induction of a moving charge in a magnetic field is based on the electron’s magnetic moment. The magnetic field turns the magnetic moment of the electron in the direction of the magnetic field. The motion of the electron undergoes a - predictable and perpendicular on the two vectors of the velocity and the magnetic field - acceleration according to the cross product of this two vectors. This acceleration leads out to the emission of a photon from the electron (Bremsstrahlung). As the photon has a pulse, this pulse reduces the velocity of the electron, and also acts against the momentum change of the electron’s magnetic moment by the external magnetic field gyroscope effect. This process is repeated periodically until the kinetic energy of the electron is consumed.

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    $\begingroup$ [citation needed] $\endgroup$ – ACuriousMind Oct 20 '14 at 18:05

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