Polarization

With the term polarization is defined – in general – the process as a result of which a concentration of “effects” is manifested towards particular points (called poles) of a system. It can assume different meanings and definitions depending on the field (scientific or humanistic).

In electrochemistry, polarization is a dissipative phenomenon that involves the decrease of the efficiency of electrochemical processes, slowing down the progress of electrode reactions and giving rise to falls in the electric potential difference (surges); the surges involve in turn heat generation due to their dissipative nature and represent deviations from the equilibrium conditions of the electrochemical cell.

In biology, we speak of polarization as a persistent and asymmetric distribution of structures along an axis, and this definition is applicable to polarity at the level of organelles, cells, organs, and whole organisms, in ovogenesis, and in general in the behaviors of one or more cells manifesting poles of activity. The establishment and maintenance of cell polarity relies on an asymmetric distribution of cytoskeleton and other protein activity within the cell. The concentration of specific proteins in a given cellular region is an essential part of the process. Polarity is central to the development of plants and animals (as well as humans), both in their evolution and in the production of individual complexity. Polarity at the level of the individual cell is central to the development of complex multicellular organisms, since the division of a polar cell generates nonequivalent daughter cells, allowing subsequent differentiated development. Although in many systems, the generation of a polar axis requires asymmetric input, some polar biological structures develop independently. Polar axis development, however, requires, in most cases, an input produced by a biological signal or the physical environment, particularly a slight gradient or gravitational stimulus.

In computer science, the polarization of a number is used in the representation of floating-point numbers in the IEEE 754 standard.

In sociology, polarization of opinion within a society is referred to; it identifies the concentration of opposing values and ideas within the society, thus the tendency of the population to side with one of the two poles. In this sense, populism in support of the ends of the camps favors and feeds the polarization of societies.

Polarization typologies

Electric polarization

In Electrostatics is defined polarization the phenomenon of redistribution of electric charges in a material body, to form electric dipoles, caused by the proximity of a charged body (source of the electric field responsible).

The electric polarization is manifested in particular in insulating materials, and generates the presence of an additional electric field inside them.

In Electrochemistry, on the other hand, electrical polarization is a phenomenon that tends to reduce the efficiency of electrochemical processes, thus slowing down the progress of electrode reactions and giving rise to falls in the electric potential difference; such falls are called “surges”. Surges in turn involve heat generation due to their dissipative nature and represent deviations from the equilibrium conditions of the electrochemical cell.

When polarization occurs at the surface of a metal, it slows down its corrosion. An example in this sense is represented by the phenomenon of passivation.

Magnetic polarization

Magnetic polarization is a phenomenon that occurs in some materials in the presence of an external magnetic field, and through which it is possible to describe the magnetism inside the matter (it expresses the density of permanent or induced magnetic dipole moments in a magnetic material).

The origin of magnetic moments responsible for magnetization can be due to microscopic electric currents resulting from the movement of electrons in atoms, or from the spin of electrons or nuclei.

Materials subject to polarization are divided into three categories: diamagnetic, paramagnetic and ferromagnetic. Paramagnetic materials have a weak induced magnetization, which disappears when the magnetic field is removed. Ferromagnetic and ferrimagnetic materials have strong magnetization and can be permanently magnetized. Magnetization is not necessarily uniform within a material, but can vary between different locations.

Polarization of electromagnetic radiation

Polarization of electromagnetic radiation is a characteristic of electromagnetic waves and indicates the direction of oscillation of the electric field vector during wave propagation in space-time (the magnetic field will be polarized along the direction orthogonal to that of the electric field and the direction of propagation).

Polarization by chemical reaction

Polarization for chemical reaction is defined as the type of electrical polarization that is activated when the kinetically determinant stage of the electrochemical process is represented by the development of a chemical reaction (without charge transfer) that precedes or follows the electrode reaction (with charge transfer).

Activation polarization

Activation polarization (or charge transfer polarization) is defined as that type of electrical polarization which is activated when the kinetically determining stage of the electrochemical process is represented by an electrode reaction (which occurs with charge transfer).

Concentration polarization

Concentration polarization (or mass transfer or diffusion polarization) is defined as the type of electrical polarization that is activated when there is a concentration gradient of the reactants between the bulk of the electrolyte and the part of the electrolyte near the electrode surface.

Ohmic polarization

Ohmic polarization is defined as the type of electrical polarization that is activated when there is heat dissipation due to the Joule effect.

Polarization by crystallization

Polarization by crystallization is defined as the type of electrical polarization that is activated when part of the potential difference, is used to move the metal atoms on the surface of the electrode (according to the steps indicated in the model Terrace Ledge Kink – TLK).

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