# Electromagnetism [electromagnetics]

Electromagnetism is the branch of classical physics that studies electromagnetic interaction and constitutes a fundamental theory that allowed to explain natural phenomena such as electricitymagnetism, and light; it is the first example of unification of two different forces, the electric and the magnetic one.

In applied engineering, electromagnetics is the study of those aspects of electrical engineering in situations in which the electromagnetic properties of materials and the geometry in which those materials are arranged is important. This requires an understanding of electromagnetic fields and waves, which are of primary interest in some applications.

Electromagnetic phenomena are defined in terms of the electromagnetic force, sometimes called the Lorentz force, which includes both electricity and magnetism as different manifestations of the same phenomenon. The electromagnetic force plays a major role in determining the internal properties of most objects encountered in daily life:

• the electromagnetic attraction between atomic nuclei and their orbital electrons holds atoms together;
• electromagnetic forces are responsible for the chemical bonds between atoms that create molecules, and intermolecular forces;
• the electromagnetic force governs all chemical processes, which arise from interactions between the electrons of neighboring atoms.
• other forces (e.g., friction, tension, and contact forces) are derived from electromagnetic forces (and the other fundamental forces).

From electromagnetic theory originate important theoretical and applicative branches concerning electric current through the circuit theory, electrical engineering, and electronics.

Usually, electromagnetism refers to classical theory, summarized in Maxwell’s equations. This theory accurately describes physical reality down to quantum dimensions: the extension of the theory also on a quantum scale is called quantum electrodynamics; the study of electromagnetism combined with special relativity leads instead to classical electrodynamics.

## Electromagnetic interaction

The electromagnetic interaction is responsible for the chemical properties of atoms and the structure of molecules. The electric charge determines the intensity and the direction of the interaction between charged bodies, bodies with equal electric charges repel each other, while bodies with opposite electric charges attract each other.

The electromagnetic force is the result of local interaction between charged bodies and the electromagnetic field. The electromagnetic field propagates like a wave, such as radio waves and the light. Even the electromagnetic interaction has infinite interaction radius, for example, the light emitted by the stars of the most distant galaxies arrives at Earth and interacts with the atoms of the atmosphere, our eyes, and telescopes.

The electromagnetic interaction has little influence in determining the structure of planetary systems, galaxies, and more generally of the universe on a large scale. In fact, the stars, planets, and galaxies are objects globally devoid of electric charge, so that the interaction between these celestial bodies is dominated by the force of gravity.

## Related keywords

• Electromagnetic field
• Electromagnetic compatibility (EMC)