Helmholtz coil with a ferrous core

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Discussion Overview

The discussion centers on the effects of incorporating a ferrous core into a Helmholtz coil design, specifically regarding the creation of a uniform magnetic field and the modifications to the magnetic field equation. The scope includes theoretical considerations and practical implications of using ferrous materials in electromagnet design.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Mike questions whether a uniform magnetic field can still be achieved with a ferrous core in a Helmholtz coil and how the magnetic field equation would change.
  • One participant seeks clarification on whether the goal is to generate a uniform field inside an object.
  • Mike clarifies that the intention is to create a uniform field between a pair of electromagnets, similar to that produced by Helmholtz coils.
  • Another participant discusses the historical use of iron yokes in NMR applications, noting that they can significantly increase field strength and affect homogeneity based on the design of the pole pieces and saturation magnetization of the iron.
  • This participant suggests that designing a high-quality magnet requires extensive knowledge of electromagnetism and materials, and recommends further study for a deeper understanding.
  • They also mention that if homogeneity and efficiency are not primary concerns, experimentation may yield interesting results.

Areas of Agreement / Disagreement

The discussion does not reach a consensus on the effects of using a ferrous core in a Helmholtz coil, as various viewpoints are presented regarding field uniformity and design considerations.

Contextual Notes

Participants express uncertainty about the implications of using a ferrous core, particularly regarding the homogeneity of the magnetic field and the specific changes to the magnetic field equation. The discussion highlights the dependence on design factors such as pole piece size and saturation magnetization.

miloko
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Dear all,
I know that I can create a uniform field using the design of a Helmholtz coil with an air-core. However, if I use a ferrous core like iron, will I still be able to create a uniform field under the same conditions? Also, how is the equation for the magnetic field, B, changed when I add a ferrous core to the center of a Helmholtz coil?

Thanks in advance,
Mike
 
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Are you trying to generate a uniform field inside the object?
 
No. I am trying to create a uniform field between a pair of electromagnets just like the field inbetween any pair of helmholtz coils. Thanks.
 
This type of magnet used to be universally used for NMR, and can still be purchased, e.g.
http://www.walkerldjscientific.com/Products/Product_Lines/Electromagnetics/electromagnetics.html"

The iron yoke concentrates all of the return flux lines, dramatically increasing the field strength in the useful region, and the two poles concentrate the flux even further. To design a high quality magnet takes more knowledge of electromagnetism and materials than can be provided in a post. Homogeneity depends critically on the size and shape of the pole pieces, and how close to saturation magnetization the iron is, for instance. Suggest you get a copy of a text like Reitz and Milford, Foundations of Electromagnetism, and do some background study. Then take a look online at sites like
http://www.geocities.com/CapeCanaveral/2404/Elect67.htm"

Of course if you aren't too concerned about homogeneity, field strength, electrical efficiency, etc., you can just fool around and see what results.
 
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