Theories and Materials

• Facts about magnetic field lines

  • Do not cross one another
  • Are continuous and form "closed loops"
  • Leave the north-seeking pole and enter the south-seeking pole
  • Are closer together in areas where the magnetic force is stronger
• Magnetic domains by Wilhelm Eduard Weber


  Each atom of a magnetic material is a magnet in itself. These atoms arranged themselves into groups called magnetic domains.
• Atoms in a magnetic material

  • Each atom is a magnet in itself
• Modern theory of magnetism by Hans Christian Oersted


  Magnetism results from moving and spinning electrons.

  
  

  1. Moving charge produces a magnetic field

  2. An electron is a charged particle that spins about its axis as it revolves around the nucleus

  3. If an atom has more electrons spinning in one direction than the other, the atom is magnetized
• Types of magnetic materials

  • Ferromagnetic
  • Paramagnetic
  • Diamagnetic
• Ferromagnetic materials

  • Strongly attracted by a magnet
  • Examples: Iron, cobalt and nickel
  • Contain some unpaired electrons, thus, their atoms initially have magnetic properties even in the absence of external magnetic field
• Paramagnetic materials

  • Have net magnetic moments due to unpaired electrons
  • Weakly attracted to magnets
  • Become more magnetic when cooled
  • Examples: Transition metals such as Palladium, platinum, and actinicide
• Diamagnetic materials

  • Weakly respond to a magnetic field
  • Magnetization exists only when an external magnetic field is applied
  • Instead of being attracted, they are repelled by a magnetic field
• Earth's magnetism is due to the motion of charged particles in its liquid outer core. Earth's rotation produces moving charged particles within it, which in turn produces a magnetic field.