Physics 1402A/B Lecture Notes - Lecture 18: Magnetic Domain, Ferromagnetism, Net Force

• School: Western University
• Department: Physics
• Course: Physics 1402A/B
• Professor: Johnde Bruyn

Document Summary

The magnetism of magnetic materials results from atomic-scale current loops. An electron orbiting a nucleus constitutes a simple current loop and has a magnetic dipole moment an electron possesses an intrinsic magnetic dipole moment associated with a quantum- mechanical angular momentum called spin. Interactions among these magnetic moments determine the magnetic properties of atoms and of bulk matter. Strong interactions among atomic magnetic moments result in magnetic domains, regions that contain atoms whose magnetic moments are all aligned in the same direction. Normally the magnetic moments of different domains point in random directions, so there"s (cid:374)o (cid:374)et (cid:373)ag(cid:374)eti(cid:272) (cid:373)o(cid:373)e(cid:374)t, (cid:271)ut (cid:449)he(cid:374) a(cid:374) e(cid:454)ter(cid:374)al (cid:373)ag(cid:374)eti(cid:272) field is applied, the domains all align and the material acquires a net magnetic moment. If the field is nonuniform, the material experiences a net force, which is why ferromagnetic materials are attracted to magnets. Hard ferromagnetic materials retain their magnetism even after the applied field is removed; the result is a permanent magnet.