What is Electrical Conductivity?

What Does Electric conductivity Mean

We explain what electrical conductivity is and based on what it varies. Electrical conduction of metals, water and soil.

Conductivity varies depending on the state of matter.

What is electrical conductivity?

Electrical conductivity is the ability of matter to allow the flow of electrical current through its particles . This capacity depends directly on the atomic and molecular structure of the material, as well as other physical factors such as the temperature at which it is found or the state in which it is ( liquid , solid , gaseous ).



Electrical conductivity is the opposite of resistivity , that is, the resistance to the passage of electricity in materials . There are then good materials and bad electrical conductive materials, insofar as they are more or less resistant.

The symbol to represent conductivity is the Greek letter sigma ( σ ) and its unit of measurement is the siemens per meter (S / m) or -1 ⋅ m -1 . For its calculation, the notions of electric field (E) and conduction current density (J) are also usually taken into account , as follows:

J = σE, from where: σ = J / E

Conductivity varies depending on the state of matter . In liquid media, for example, it will depend on the presence of dissolved salts in them that generate positively or negatively charged ions , and are the electrolytes responsible for conducting the electric current when the liquid is subjected to an electric field.

Instead, the solids have a much tighter and less atomic structure movement , so the conductivity depends on the cloud electrons shared bands valence and the conduction band, which varies the atomic nature of matter: the Metals are good electrical conductors and non-metals , on the other hand, good resistance (or insulators, like plastic ).

See also: Thermal conductivity

Water conductivity

The water generally is a good electrical conductor. However, this capacity depends on its margin of Total Dissolved Solids (TDS) , since the presence of salts and minerals in the water forms the electrolytic ions that allow the passage of electric current. Proof of this is that distilled water , which is eliminated (using distillation and other methods) all the ions dissolved in it, and does not conduct electricity.

In this way, the conductivity of salt water is higher than that of fresh water . The increase in the conductivity rate can be recorded as dissolved ions are added to the liquid, until reaching a limit of ionic concentration in which pairs of ions are formed, positive with negative, which cancel their charge and prevent conductivity. increase more.

Soil conductivity

More saline soils will be better electrical conductors.

The soils generally have different electrical conductivity, depending on various factors such as water irrigation or the amount of salts present. As in the case of water, the more saline soils will be better electrical conductors than the less saline ones , and this distinction is often determined by the amount of water they receive (since the water can “wash” the salts from the soil).

This level of salinity is often confused with the sodicity of the soil (the presence of sodium), when in reality salinity refers to the abundance of the cations of sodium (Na + ), potassium (K + ), calcium (Ca 2 + ) and magnesium (Mg 2+ ), together with the cations of chlorine (Cl - ), sulfate (SO 4 2- ), bicarbonate (HCO 3 - ) and carbonate (CO 3 2- ).

Thus, in many cases techniques such as washing (for very saline soils) or the injection of other neutralizing elements (such as sulfur) are used for very basic ones. This can often be determined by electrical conduction tests.

Metal conductivity

Metals are generally excellent electrical conductors . This is because the atoms of this type of material combine by forming metallic bonds . In metals, electrons remain around the metal like a cloud, moving around tightly bound atomic nuclei, and it is they that allow electrical flow.

When metal is applied to an electric field, electrons flow freely from one end of the metal to the other, as also happens with heat , of which they are both good transmitters. That is why copper and other metals are used in power lines and electronic devices. The following figure schematically represents the flow of electrons (in red) when an electric field is applied to a metal.

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