Electromagnetism is the physics of the electromagnetic field, a field which exerts a force on particles with the property of electric charge and which is reciprocally affected by the presence and motion of such particles.
A changing magnetic field produces an electric field (this is the phenomenon of electromagnetic induction, the basis of operation for electrical generators, induction motors, and transformers). Similarly, a changing electric field generates a magnetic field.
The magnetic field is produced by the motion of electric charges, i.e., electric current. The magnetic field causes the magnetic force associated with magnets.
The theoretical implications of electromagnetism led to the development of special relativity by Albert Einstein in 1905; and from this it was shown that magnetic fields and electric fields are convertible with relative motion as a four vector and this led to their unification as electromagnetism.
Until 1820, the only magnetism known was that of iron magnets and of "lodestones", natural magnets of iron-rich ore. It was believed that the inside of the Earth was magnetized in the same fashion, and scientists were greatly puzzled when they found that the direction of the compass needle at any place slowly shifted, decade by decade, suggesting a slow variation of the Earth's magnetic field. 
André-Marie Ampère (1775-1836), was a French physicist, natural philosopher, and mathematician who is best known for his important contributions to the study of electrodynamics. He invented the astatic needle, a critical component of the modern astatis galvanometer, and was the first to demonstrate that a magnetic field is generated when two parallel wires are charged with electricity. He is generally credited as one of the first to discover electromagnetism. Ampère's most significant scholarly paper on the subject of electricity and magnetism, titled Memoir on the Mathematical Theory of Electrodynamic Phenomena, was published in 1826. The theoretical foundation presented in this publication served as the basis for other ideas of the 19th century regarding electricity and magnetism. It helped to inspire research and discoveries by scientists including Faraday, Weber, Thomson, and Maxwell. 
- Electromagnetic Force
- Classical electrodynamics
- Photoelectric effect
- Magnetic flux
- Cogging torque
- Magnetic reluctance
- Torque ripple
- ↑ Bellis, Mary., History of Electromagnetism - Innovations Using Magnetic Fields: The innovations of Andre Marie Ampere and Hans Christian Oersted http://inventors.about.com/od/estartinventions/a/Electromagnets.htm, 1997
- ↑ André-Marie Ampère Bio, National Imports LLC, http://www.rare-earth-magnets.com/t-andre-marie-ampere.aspx, 2010