Magnet

Magnetic potential of a magnetized material

In Coulomb gauge, the potential due to a magnetized magnet Ω is given by

⃗𝐀(⃗𝐫)=𝜇04𝜋∭Ω⃗𝐌(⃗𝐫′)׈𝖗𝔯2𝑑𝜏′=𝜇04𝜋⊂⊃∬𝜕Ω⃗𝐊𝑏(⃗𝐫′)𝔯𝑑𝑎′+𝜇04𝜋∭Ω⃗𝐉𝑏(⃗𝐫′)𝔯𝑑𝜏′

where ⃗𝐌 is the magnetization, and ⃗𝐊𝑏 and ⃗𝐉𝑏 are the surface and volume bound current densities respectively given by

⃗𝐊𝑏(⃗𝐫′)=⃗𝐌(⃗𝐫′)׈𝐧⃗𝐉𝑏(⃗𝐫′)=⃗∇×⃗𝐌(⃗𝐫′)

If additional free current is present, the principle of superposition may be used to combine the potentials due to free current and due to magnetization (i.e. bound current).

Derivation

Applying ^GE5

⃗𝐀(⃗𝐫)=𝜇04𝜋∭Ω⃗𝐌(⃗𝐫′)׈𝖗𝔯2𝑑𝜏′=𝜇04𝜋∭Ω⃗𝐌(⃗𝐫′)×⃗∇′[𝔯−1]𝑑𝜏′=𝜇04𝜋⊂⊃∬Ω⃗𝐌(⃗𝐫′)×𝑑⃗𝐚𝔯𝑑𝜏′+𝜇04𝜋∭Ω⃗∇×⃗𝐌(⃗𝐫′)𝔯𝑑𝜏′

as required.


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