Summary
- The term electromagnetism is a blanket term for all possible types of interactions that can exist between electric charges.
- Electricity and magnetism are related phenomena, however when…
- charges are at rest the phenomena are generally described as electric or electrostatic
- The source of all electric phenomena is electric charge.
- charges are in motion and the magnitude of the current is constant the phenomena are generally described as magnetic or magnetostatic
- The source of all magnetic phenomena is moving electric charge.
- charges are in motion and the magnitude of the current is varying with time the phenomena are generally described as electromagnetic
- The source of all electromagnetic phenomena is accelerating electric charge.
- 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 electric motors and electric generators.
- 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.
- Time varying fields
- A changing electric field will produce a magnetic field.
- A changing magnetic field will produce an electric field.
- Waves
- An electromagnetic wave is any disturbance in the electric and magnetic fields that propagates.
- All electromagnetic waves propagate at the speed of light in a vacuum.
- The seemingly disparate phenomena of electricity, magnetism, and optics are all related aspects of the larger phenomenon of electromagnetism.
- This last statement was predicted mathematically before it was determined experimentally.
- Electromagnetic waves can have any wavelength or frequency.
- Light is an electromagnetic wave that is visible to the typical human eye.
- There are electromagnetic waves other than light.
- The full range of frequencies or wavelengths of electromagnetic waves is called the electromagnetic spectrum.
- The currently agreed upon, major named bands of the electromagnetic spectrum are, in order of increasing frequency…
- radio waves
- microwaves
- infrared (ir)
- light (sometimes specifically called visible light)
- ultraviolet (uv)
- x-rays
- gamma rays (γ)
- Where one band ends and another begins depends on custom, language, culture, law, history, and some science.
- Smaller divisions of the spectrum are possible to whatever degree suits a particular technology or field of study.
