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PRACTICE / Magnetic materials

The field inside a magnetized sphere

A uniformly magnetized sphere is described by the hypothetical linear law M = χHᵢₙₜ with χ = 6. Its demagnetizing factor is D = 1/3, and a uniform applied field is Hₐₚₚ = 90 A/m.

What is the internal H field along the applied-field direction?

Organize the givens & assumptions
  • χ = 6
  • Sphere demagnetizing factor: D = 1/3
  • Hₐₚₚ = 90 A/m

SI convention Hᵢₙₜ = Hₐₚₚ − DM; linear isotropic response over the given range, uniform ellipsoidal model. This is an assigned constitutive law, not a claim that a real ferromagnet has constant χ.

  1. A30 A/m30\ \mathrm{A/m}
  2. B90 A/m90\ \mathrm{A/m}
  3. C180 A/m180\ \mathrm{A/m}
  4. D540 A/m540\ \mathrm{A/m}

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