Electromagnetism

Summary

• Electricity and magnetism are related phenomena.
  • The source of all magnetism is moving electric charge.
• Electromagnetic forces
  • Charged objects exert electric forces on one another (sometimes called electrostatic forces).
    • This is the principle behind static cling and why electrons are bound to the nucleus of an atom.
  • Magnets exert magnetic forces on one another.
    • This is the principle behind compasses and refrigerator magnets.
  • Magnets exert magnetic forces on moving charges.
    • This is the principle behind an electric motor, or the deflecting coils in a cathode ray tube (CRT) display.
• Electromagnetic fields
  • Electric charges are surrounded by an electric field.
  • Moving electric charges are also surrounded by a magnetic field.
    • Electric current flowing through a coil of wire is an electromagnet.
    • The spin of the electron makes it behave like a very small magnet.
    • Electric currents in the molten outer core of the Earth make it behave like a giant magnet.