How can I produce a net translational force on a ferromagnet?

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Discussion Overview

The discussion revolves around how to produce a net translational force on a ferromagnet, exploring the effects of external magnetic fields and other methods of manipulation. It touches on theoretical and conceptual aspects of magnetism and motion.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests introducing an external magnetic field to achieve translational force on a ferromagnet.
  • Another participant questions whether a constant magnetic field would produce translational motion or merely torque the magnet, expressing uncertainty about the mathematical determination of forces from the magnetic field on the ferromagnet.
  • A different participant humorously suggests physically pushing the magnet to create motion, while also acknowledging that a uniform magnetic field generally produces torque rather than translation.
  • It is noted that most external magnetic fields are not uniform, which can lead to translational motion as one pole of the magnet moves closer to a stronger field.
  • A participant introduces an example of aquatic bacteria that utilize internal ferromagnets for orientation and movement, explaining how they align with the Earth's magnetic field but do not experience translational force from it.

Areas of Agreement / Disagreement

Participants express differing views on the effects of external magnetic fields on ferromagnets, with some agreeing that uniform fields produce torque while others explore the conditions under which translational motion might occur. The discussion remains unresolved regarding the specific conditions necessary for producing a net translational force.

Contextual Notes

Participants express uncertainty about the mathematical relationships between magnetic fields and forces on ferromagnets, indicating that assumptions about uniformity and field strength may influence outcomes.

endersdouble
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How can I produce a net translational force on a ferromagnet?
 
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I think that's analogous to asking how you balance an egg on the tip of a pen.
 


Originally posted by endersdouble
How can I produce a net translational force on a ferromagnet?

Introduce an external magnetic field.
 
Any external field? I had some idea that a constant field would only torque the magnet, not put a translational on it...but not sure how to mathematically determine forces from field B on a ferromagnet M.
 


Originally posted by endersdouble
How can I produce a net translational force on a ferromagnet?

Uhh; push it with your finger!


... I had some idea that a constant field would only torque the magnet, not put a translational on it...but not sure how to mathematically determine forces from field B on a ferromagnet M.

Oh, you mean produce translational motion using an external field? :wink:

You are correct; generally a uniform magnetic field only produces a torque. However, most external fields are not uniform over much of a distance; so when the poles of the magnet rotate usually one pole is 'closer' to the stronger external pole and the entire magnet translates in that direction.

However, in a large B field like the earth, small magnets have no translational motion.

There is a species of aquatic bacteria that has been found to have a built-in string of 'permanent' ferromagnets inside it (about 1 micron in diameter) pointing with the North pole facing toward its 'head'.
The Earth's field doesn't 'pull' it either way, but simply rotates it to align with the Earth's North field. The bacteria has flaggella in its 'rear' that propells it forward as it points toward the Earth's North pole, which by the way, is on an angle into the earth. So the bacteria always burrows into the slim beneath the waters, keeping it away from the upper oxygen rich water that is toxic to them. Quite an interesting internal guidance system.


Creator
 
Last edited:


Originally posted by Creator

There is a species of aquatic bacteria that has been found to have a built-in string of 'permanent' ferromagnets inside it (about 1 micron in diameter) pointing with the North pole facing toward its 'head'.
The Earth's field doesn't 'pull' it either way, but simply rotates it to align with the Earth's North field. The bacteria has flaggella in its 'rear' that propells it forward as it points toward the Earth's North pole, which by the way, is on an angle into the earth. So the bacteria always burrows into the slim beneath the waters, keeping it away from the upper oxygen rich water that is toxic to them. Quite an interesting internal guidance system.

Creator
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