What is the unit for electrical conductivity

Specific conductance or electrical conductivity κ (kappa)

The suitability of various substances for conducting electricity is determined by the number and mobility of the free charge carriers in them. Since the conductivity, i.e. the mobility of free charge carriers, depends on the temperature, the conductivity is given at a temperature of 25 ° C.

In the case of solids, especially metals, there is a close relationship between electrical conductivity and thermal conductivity. Good electrical conductors are also good heat conductors.
The electrical conductivity of solid bodies has a range of 24 powers of ten at room temperature. This leads to a division into three electrical substance classes.

Conductor (metals)semiconductorNon-conductors (insulators)
 Gallium arsenide 

Conductor (metals)

A distinction is made between electron conductors and ion conductors. Electron conductors consist of metal atoms that form a firm bond with one another. Their valence electrons are released. The valence electrons are the electrons on the outermost shell of the atom. This turns the atoms into positive ions. The ions are evenly spaced from one another and form a grid in which the free electrons move like a cloud (electron gas). The negatively charged electron cloud holds the positively charged ions together.

If the conductor is exposed to an electrical voltage, the electrons move in a certain direction. A current of electrons flows from the negative pole to the positive pole.
In metals, the number of free charge carriers is very large (one free electron per atom). Their mobility is restricted and their electrical conductivity is high. The conductivity of good conductors is 106 Siemens / cm.
The current that flows when a voltage is applied is nothing other than the large amount of elementary charges. An electron is with 10-19 Coulomb involved. If by a ladder for a second 1019 Electrons flow, then you can measure a current of 1 ampere.
It should be noted that the flow of electrons does not cause any change in the metal. It is different in the ion conductor. These are conductive liquids (electrolytes), melt and ionized gases. The charge carriers are both positive and negative ions. The ion current changes the substance.

Non-conductors (insulators)

The non-conductors include solid substances such as plastic, rubber, glass, porcelain, paper, liquids such as pure water (H.2O), oils and fats, but also vacuum and gases under certain conditions.
Usually insulators or insulating materials are used to electrically separate electrical conductors from one another (insulate).
In insulators, the number of free charge carriers is zero. The electrical conductivity is therefore negligibly low. The conductivity of good insulators is 10-18 Siemens / cm.


The electrical conductivity of semiconductors is between that of metals and insulators. Semiconductors differ from conductors in that the valence electrons are only released by external influences such as pressure, temperature, exposure or magnetism and only then does conductivity begin.
Semiconductor materials are, for example, silicon, germanium and selenium.

Formula symbol

The symbol for electrical conductivity is κ (kappa), γ (gamma) or σ (sigma).
Usually the lower case κ is sometimes also used γ (gamma). Unfortunately this is nowhere precisely defined.

Unit of measurement

The unit of measurement of electrical conductivity is

Calculation formulas

The electrical conductivity is the reciprocal of the specific resistance. Hence the term specific conductivity.

Examples of the specific conductivity

Depending on the atomic structure, metallic conductors have different conductivity. Silver has the highest conductivity, closely followed by copper. That is why copper is also used as a material for metallic conductors. It's cheap and easy to make. Silver, on the other hand, is far too expensive and cannot be used for stranded cables. Only when a very high conductivity is required, especially on the outer skin (skin effect), is the copper wire coated with silver.

It is generally interesting that every semiconductor becomes more conductive when heated, because more charge carriers are released. With a leader it is exactly the opposite. The conductivity decreases because there are no longer any free charge carriers. But the free charge carriers hit the atomic shell at a higher temperature and this ultimately increases the electrical resistance.

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