Physics II / Magnetic Materials
Practice question · Multiple choice

Why does magnetostatics introduce the auxiliary field H\mathbf{H}?

Hints
  1. Compare with the role of the displacement field in electrostatics.
  2. Bound currents are hard to track; free currents are what you supply.
Show the answer

D. Its curl counts only free current, so Ampère’s law stays usable in matter

Why

×H=Jf\nabla\times\mathbf{H} = \mathbf{J}_f hides the bound magnetisation currents, so Ampère’s law can be applied with only the current you actually drive. Force on a moving charge is still qv×Bq\mathbf{v}\times\mathbf{B}.

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