# Electromagnetism

The electromagnetism is a branch of the Physique which provides a very general framework of study of the Phénomène S electric S and magnetic S in their synthesis of the electromagnetic Champ, produced by the sources of the field which are the loads and their movements. This produced field acts in its turn on the loads.

• the Maxwell's equations determine the electromagnetic field starting from the sources, of the loads and the currents. The field exerts as for him on the matter a mechanical action, the Force of Lorentz, which explains the electromagnetic interaction.

• the electromagnetic interaction is one of the four fundamental interactions. She explains the behavior of the objects of the atomic scale (behavior of the electron S, the atoms and the Molécule S).

## History

Electromagnetism was born from the unification by James Maxwell of former theories, like the electrostatic , the electrokinetic or the Magnétostatique. This unified theory explains inter alia the behavior of the loads and electric currents, of the Aimant S, or the electromagnetic waves, the such Lumière or the waves radio.

The fundamental concept of the theory is the electromagnetic concept of Champ, entity which includes the Electric field and the Magnetic field, which is reduced in certain particular cases:

1. the loads are motionless: one is then in electrostatic with static electric fields.
2. the Density of load is null and the currents are constant in time: one is in Magnétostatique with a static magnetic field.
3. When the currents are relatively weak and variable and in isolated drivers known as electric wires move, the produced magnetic fields are very localized in elements known as reels of self-inductance, coil, transformers or generators and the densities of nonnull loads in condensers or generating batteries of currents: one is then in electrokinetic; one distinguishes there the low currents (electronic) and the high tension currents (electrotechnical). There is no field outside the circuit. electrical circuits are studied and one distinguishes the low frequencies and the high frequencies there. Electronics made enormous progress starting from the development of the Semi-conducteur S which are now used to make Integrated circuits increasingly miniaturized and comprising electronic chips or Microprocesseur S.
4. the high frequencies reached by the resounding circuits electric made it possible, using antennas, to create electromagnetic waves thus eliminating wire from connections. The emission, the propagation and the reception of these waves which are controls by the Maxwell's equations constitute electromagnetism.

The electromagnetic interaction presented in fundamental terms of the Theoretical physics or fundamental Physique is called the electrodynamic ; if one takes account of the aspect Quantique, it is the electrodynamic quantum relativist.

This formalism is similar to that of quantum mechanics: the resolution of the equation of Schrödinger, or its relativistic version (the equation of Dirac), gives the probability of presence of the electron and the solution of the Maxwell's equation, interpreted a long time like a wave, is at the base an equation of probability for the Photon, which has neither load nor mass and which moves only with the Speed of light in the vacuum.

## Various fields

The electromagnetism includes electricity, gathering the electric and magnetic phenomena following:
• the electrostatic : Electric systems of charges to the équilibre  ;
• the Magnetostatic : Phenomena created by a stationary electric current; ;
• the magnetic Induction: Magnetic phenomena created by a variable electric current;
• the electrodynamic : Dynamic interactions between currents électriques  ;
• the electronic : The use of tension, generally weak currents and quantum phenomena . Electronics is useful primarily for the transfer, the control and the treatment of the Information   ;
• the electrokinetic or the electrotechnical : The use of tensions, average currents to high for applications Domestic S and Industry it (Transformer Heating, S, electrical motors, electrolysis, electric household appliances, Distribution, automation,…)  ;
• the Radioelectricity: The Transmission S by Wave S electromagnetic S.

## See too

### External bonds

• electromagnetism, Scio

• Books and course of instruction
• History of electricity, CNRS

Be-X-old: Класічнаяэлектрадынаміка Simple: Electromagnetism

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