Neutrons in electromagnetic fields

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Discussion Overview

The discussion revolves around the behavior of neutrons in electromagnetic fields, particularly in relation to a video that suggests a neutron would need to be charged to be deflected by a magnetic field. Participants explore the implications of neutron spin and magnetic moments, as well as the principles of electromagnetism and special relativity.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants question whether a neutron can be deflected by a magnetic field, suggesting that the video implies a neutron must be charged to experience such deflection.
  • Others argue that objects do not need to be charged to be deflected by a magnet, citing neutron spin as a factor that could allow for deflection.
  • A participant points out that the video may be incomplete or misleading regarding the forces acting on neutrons.
  • Some participants assert that neutrons, due to their magnetic moments, should deflect under certain conditions, while others challenge this view by referencing the nature of the magnetic fields involved.
  • There is a discussion about the differences between the effects of uniform and non-uniform magnetic fields, with references to the Stern-Gerlach experiment as a counterexample.
  • One participant emphasizes the importance of mathematical analysis or experimental evidence over analogies in understanding the behavior of neutrons in magnetic fields.

Areas of Agreement / Disagreement

Participants express differing views on whether neutrons can be deflected by magnetic fields, with no consensus reached on the implications of the video or the underlying physics principles.

Contextual Notes

Participants note limitations in the video’s explanation and the need for careful consideration of the specific conditions under which neutrons might be deflected, including the nature of the magnetic fields and the assumptions made about charge and magnetic moments.

Danyon
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Consider a moving neutron passing by an electromagnet, will a neutron be deflected? This video seem to show that the neutron would have to be charged in order for it to move
 
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This video seem to show that the neutron would have to be charged in order for it to move
How? When?

Note: Objects do not have to have a charge to be deflected by a magnet.
http://www.phys.utk.edu/witek/np621/symmetrytests.pdf
... see section on neutron spin: they are little magnets.
... directly after that, see the brute force measure for neutron neutrality.
 
Last edited by a moderator:
Simon Bridge said:
How? When?

Note: Objects do not have to have a charge to be deflected by a magnet.
http://www.phys.utk.edu/witek/np621/symmetrytests.pdf
... see section on neutron spin: they are little magnets.
... directly after that, see the brute force measure for neutron neutrality.
The video implies that the neutron would have to be charged at 2:44 The proton in the video moves because it is electrostatically repelled by the length contracted Protons in the wire. A neutron, being neutral, cannot experience this force.
 
Last edited by a moderator:
If a neutron were to experience the force being illustrated, then it would have to be charged. But there is nothing there to indicate that the neutron experiences the force being illustrated.

Basically you are noticing that the video is incomplete.
Did you read the link?
 
Simon Bridge said:
If a neutron were to experience the force being illustrated, then it would have to be charged. But there is nothing there to indicate that the neutron experiences the force being illustrated.

Basically you are noticing that the video is incomplete.
Did you read the link?
"Objects do not have to have a charge to be deflected by a magnet." I was aware of this, I was just pointing out that the mechanism described in the video seems to imply that neutrons won't deflect, when they should, showing that the special relativity explanation is inconsistent with reality,
 
"Objects do not have to have a charge to be deflected by a magnet." I was aware of this, I was just pointing out that the mechanism described in the video seems to imply that neutrons won't deflect, when they should, showing that the special relativity explanation is inconsistent with reality,
... or that the short introductory demo in a youtube video is somehow incomplete...

BTW: what makes you think that neutrons deflect in the circumstances described in the video?
 
Simon Bridge said:
... or that the short introductory demo in a youtube video is somehow incomplete...

BTW: what makes you think that neutrons deflect in the circumstances described in the video?
I just thought so since they have magnetic moments,
 
Work it out - would a neutron, in the situation that the video places a proton, be deflected by the magnetic field of the wire?
 
Simon Bridge said:
Work it out - would a neutron, in the situation that the video places a proton, be deflected by the magnetic field of the wire?
I'l say no, however, it must be deflected by permanent magnets which work on a different principle
 
  • #10
Permanent magnets use electromagnetism just like electromagnets do.
You cannot do physics by analogy - try using maths (or experiment).

In the link I gave you it shows you that neutrons are not deflected by a uniform electric field - which would need to be the case for the circumstances in the video above to show a contradiction. A neutron can be deflected by a non-uniform magnetic field - as int he Stern-Gerlach experiment. The field about a wire is non-uniform in the direction the field points in - like it is in the S-G apparatus. That is not the case for the wire.

You may want to get together with this person:
https://www.physicsforums.com/threads/two-velocities-in-the-lorentz-law.804172/
... you are studying the same video. Perhaps you are in the same class?

It will also benefit you to get other sources.
 
  • #11
"Permanent magnets use electromagnetism just like electromagnets do." This video seems to imply that it's the intrinsic magnetic moment rather than the effects of special relativity
 
  • #12
Danyon said:
"Objects do not have to have a charge to be deflected by a magnet." I was aware of this, I was just pointing out that the mechanism described in the video seems to imply that neutrons won't deflect, when they should, showing that the special relativity explanation is inconsistent with reality,
You have to be careful not to overgeneralize small concepts. In the video they are specifically discussing the magnetic force on a point charge outside a current carrying wire. They are not even talking about the magnetic field. The magnetic force can always be made zero by transforming to a frame where the point charge is at rest, but that does not imply that the magnetic field is zero nor does it imply that the force on a magnetic dipole could be made zero.
 

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