Understanding Magnetic Dipole Fields in a Linear Magnetic Sphere

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SUMMARY

The discussion centers on calculating the magnetic field of a dipole located at the center of a linear magnetic sphere with radius R. The user initially derived a field expression involving a reduced dipole moment and an additional constant term, but found a discrepancy between their result and the one provided in a reference book. The user’s derived formula was -\frac{\mu}{4\pi}\frac{2(\mu_0 - \mu) \vec m}{(3\mu) R^3}, while the book stated -\frac{\mu}{4\pi}\frac{2(\mu_0 - \mu) \vec m}{(2\mu_0 + \mu) R^3}. Ultimately, the user resolved the issue independently, indicating a successful understanding of the problem.

PREREQUISITES
  • Understanding of magnetic dipole theory
  • Familiarity with linear magnetic materials
  • Knowledge of magnetic field equations
  • Basic calculus for handling vector equations
NEXT STEPS
  • Study the derivation of magnetic fields from dipoles in linear media
  • Explore the concept of bound surface currents in magnetic materials
  • Learn about the differences in magnetic permeability, specifically \(\mu_0\) and \(\mu\)
  • Investigate the application of superposition principles in electromagnetism
USEFUL FOR

Physicists, electrical engineers, and students studying electromagnetism, particularly those interested in magnetic fields and dipole interactions in materials.

StatusX
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I need to find the field of a magnetic dipole embedded in the center of a linear magnetic sphere of radius R. My idea was that the field would be identical to that of a superposition of a dipole in a linear magnetic material throughout space and a surface current on the sphere equal to the bound surface current from this field. The answer I get for the field insid the sphere has the reduced dipole moment term right, and I also got that the extra term would be constant, and a multiple of the dipole moment. But where as I got this for the extra term:

[tex]-\frac{\mu}{4\pi}\frac{2(\mu_0 - \mu) \vec m}{(3\mu) R^3}[/tex]

the book gave:

[tex]-\frac{\mu}{4\pi}\frac{2(\mu_0 - \mu) \vec m}{(2\mu_0 + \mu) R^3}[/tex]

Do you know what I did wrong? I'm close, and I can't find a step where a simple change will result in this small difference in the final answer. Am I way off, and its just a coincidence its so close?

EDIT: Never mind, I got it.
 
Last edited:
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StatusX said:
EDIT: Never mind, I got it.
I'm glad you got it even though it was 15 years ago. I responded just to have your post removed from the unanswered list. :wink:
 

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