Magnetism Notes

Sources of Magnetic Fields

• Electric currents create magnetic fields (Oersted effect).
• Electromagnets utilize this effect.
• Current in a wire creates a circular magnetic field.
• Current in a loop generates a magnetic field straight out of the center.
• Magnetic materials include iron, nickel, and cobalt.
• Electron spin creates a magnetic field around atoms.

Magnetic Materials

• Atoms align magnetic fields into domains.
• External magnetic fields can align domains, creating a magnet.

Direction of the Magnetic Field

• Magnetic field lines go from North to South.

Breaking a Magnet

• Breaking a magnet creates new poles.

Right Hand Rule

• For a straight wire:
  • Thumb points in the direction of positive current.
  • Fingers curl in the direction of the magnetic field.
• For a coiled wire:
  • Fingers wrap in the direction of the current.
  • Thumb points in the direction of the magnetic field.

Earth as a Magnet

• Earth's spinning core creates a magnetic field.
• The North Pole of the Earth is a south magnetic pole.

Electromagnets

• Passing current through a coil (solenoid) around iron creates a magnet.
• The magnetic field aligns domains in the iron.

Magnetic Induction

• Changing magnetic fields induce electric fields, creating currents in conductors.