Electromagnetism

Electromagnetism is a branch of Physics that studies and unifies electrical and magnetic phenomena in a single theory, its foundations were first disclosed by Michael Faraday and first formulated in its entirety by James Clerk Maxwell . The formulation consists of four vector differential equations that relate the electric field, the magnetic field, and their respective material sources (electric current, electric polarization, and magnetic polarization), known as Maxwell’s equations.

Summary

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  • 1 Theory
  • 2 History
  • 3 Electrostatics
  • 4 Other related concepts
  • 5 See also
  • 6 Bibliography
  • 7 Sources

Theory

The explanations and predictions that it provides are based on vector or tensorial physical magnitudes dependent on the position in space and time, which is why it is considered a field theory; In other words, electromagnetism describes macroscopic physical phenomena in which electrical charges intervene at rest and in motion, using electrical and magnetic fields and their effects on solid, liquid and gaseous substances. Because it is a macroscopic theory, that is, applicable only to a very large number of particles and at great distances from their dimensions, Electromagnetism does not describe atomic and molecular phenomena, for which it is necessary to use Quantum Mechanics.

This considered as force is one of the four fundamental forces of the currently known universe.

History

Magnetic and electrical phenomena were known from ancient Greece , but it was not until the beginning of the 17th century that experiments began and scientific conclusions were reached about these phenomena. During this time, great scientists such as William Gilbert, Otto von Guericke, Stephen Gray, Benjamin Franklin, Alessandro Volta among others investigated these two phenomena separately and reaching conclusions consistent with their experiments.

In the early 19th century Hans Christian Orsted found empirical evidence that magnetic and electrical phenomena were related. Hence, the works of physicists like André-Marie Ampère, William Sturgeon, Joseph Henry, Georg Simon Ohm, Michael Faraday in that century, are unified by James Clerk Maxwell in 1861 with a set of equations that described both phenomena as one. , as an electromagnetic phenomenon.

The so-called Maxwell equations showed that electric fields and magnetic fields were manifestations of a single electromagnetic field. It also described the wave nature of light, showing it as an electromagnetic wave. With a single consistent theory describing these two previously separate phenomena, physicists were able to perform several prodigious experiments and very useful inventions such as the electric light bulb by Thomas Alva Edison or the alternating current generator by Nikola Tesla . The predictive success of Maxwell’s theory and the search for a coherent interpretation of its implications was what led Albert Einstein to formulate his theory of relativity that was based on some previous results by Hendrik Antoon Lorentz and Henri Poincaré.

In the first half of the 20th century , with the advent of quantum mechanics , electromagnetism had to improve its formulation in order to make it consistent with the new theory. This was accomplished in the 1940s when an electromagnetic quantum theory or better known as quantum electrodynamics was completed.

Electrostatics

electrostatics

When we speak of electrostatics we are referring to the phenomena that occur due to an intrinsic and discrete property of matter, the charge, when it is stationary or not, it depends on time. The unit of elementary charge, that is, the smallest observable, is the charge that the electron has.

A body is said to be electrically charged when it has excess or lack of electrons in the atoms that compose it. By definition, the electron defect is called a positive charge and the excess is a negative charge. The relationship between the two types of charge is attractive when they are different and repulsive when they are the same.

electrostatics

Elemental charge is a very small unit for practical calculations, which is why in the international system the unit of electric charge, coulomb, is defined as the amount of charge of 6.25 x 1018 electrons. The movement of electrons by a conductor is called electric current and the amount of electric charge that passes per unit of time is defined as current intensity.

More concepts such as potential difference or resistance can be introduced, which would inevitably lead us to the area of ​​electrical circuits, and all of this can be seen in more detail in the main article.

Other related concepts

The name of the unit of charge is due to Coulomb who in 1785 arrived at a mathematical relationship of the electric force between point charges, which is now known as Coulomb’s law:

Between two point charges and there is an attractive or repulsive force that varies according to the square of the distance between them and of radial direction; y is a constant known as electrical permittivity.

The elemental charges not being alone should be treated as a distribution of them. That is why the concept of field must be implemented, defined as a region of space where there is a time dependent or independent scalar or vector magnitude. Thus the electric field is defined as the region of space where electric forces act. Its intensity is defined as the limit to which the force of a charge distribution tends on a positive charge that tends to zero.

It is important to know the scope of this concept of electric field, it gives us the opportunity to know what is its intensity and what happens to a charge in any part of said field regardless of the ignorance of what causes it.

One way to get how much electric force passes through a certain point or surface of the electric field is that the concept of electric flux was devised. This electric flow? It is defined as the sum of the amount of field that a given area passes through.

The mathematician and physicist, Carl Friedrich Gauss, showed that the amount of electric flux in a field is equal to the ratio of the charge enclosed by the surface on which the electric flux and permittivity are calculated. This relationship is known as Gauss’s law.

 

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