What is Electrical Conductivity? – Principle, Formula and Applications

Electrical Conductivity is an important term used in electrical engineering to understand the behavior of a material and electric current flowing through it. Electric conductivity is the property of a material that provides ease in the flow of electric current through the material.

Read this article to get a detailed understanding of "electric conductivity", from its definition to principle and its applications. Let us start with the basic definition of electrical conductivity.

What is Electrical Conductivity?

Electrical conductivity is defined as the property that provides ease in the flow of electric current (movement of electrons) through a material. Electrical conductivity is also known as specific conductance of material.

• Electrical conductivity is basically the opposite concept of "electrical resistivity", i.e., property that opposes the flow of electric current. Electrical conductivity is an intrinsic property of a material which does not get affected by any external factor.

• Electrical conductivity provides the information about how easily the electric current can flow through a material when a potential difference or voltage is applied across it.

The materials that have higher electric conductivity allow the passing of electric current through them with minimal resistance. Therefore, a material which has very high conductivity considered a perfect conductor of electricity. On the other hand, a material having lower electrical conductivity offers high resistance to the flow of current and is considered a poor conductor of electricity.

Electrical conductivity plays a vital role in classifying electrical materials.

• If a material has very high electrical conductivity, then it is classified as a conductor.

• A material with lowest electrical conductivity is classified as an insulator.

• The material which has electrical conductivity between conductors and insulators is classified as a semiconductor.

Principle behind Electrical Conductivity

As per electron theory of matter, every material is made up of sub-atomic particles namely, electrons, protons, and neutrons. Where, protons and neutrons are tightly bound in the nucleus of the atom and the electrons can move around the nucleus in different orbits.

In an atom, electrons are arranged according to their energy levels in different orbits. These electrons can move when an electric field is applied. When an external voltage or field is applied, these electrons being charged particles get movement. Since electrons are negatively charged particles, they move toward the positive terminal of the source. This is how electric current flows through a material and the property of material by which these electrons can move through the material is called electrical conductivity.

Therefore, the fundamental principle behind the electrical conductivity is the ease of movement of electrons through a material.

Formula of Electrical Conductivity

As we have discussed above that the electrical conductivity is the opposite concept of electrical resistivity. Thus, mathematically, the electrical conductivity can be defined as the reciprocal of resistivity, i.e.,

$$\mathrm{\sigma \: = \: \frac{1}{p}}$$

Where, $\mathrm{\sigma}$ is the electrical conductivity and ρ is the electrical resistivity.

The electrical resistivity is also given by,

$$\mathrm{p \: = \: \frac{Ra}{l}}$$

Where, R is the resistance of the material, a is the cross-section area and l is the length of the conductor.

Hence, the electrical conductivity can also be given by,

$$\mathrm{\sigma \: = \: \frac{l}{Ra}}$$

Thus, we can calculate the electrical conductivity of any substance using these formulae.

Unit of Electrical Conductivity

As the electrical conductivity is given by,

$$\mathrm{\sigma \: = \: \frac{l}{Ra}}$$

Hence, the unit of electrical conductivity can be derived as follows,

$$\mathrm{Unit \: of \: \sigma \: = \: \frac{m}{\Omega \: \times \: m^{2}} \: = \: \Omega^{-1}m^{-1}}$$

Hence, the unit of conductivity is Mho per meter.

Sometimes, another unit of conductivity is used which is Siemens per meter (S/m).

$$\mathrm{1 \: Sm^{−1} \: = \: 1 \: \Omega^{-1}m^{-1}}$$

Electrical Conductivity of Different Materials

The electrical conductivity is the property of a material which depends on the nature of the material. Therefore, different materials have different electrical conductivity.

The electrical conductivity of some commonly used materials is given in the following table −

Material	Electrical Conductivity (S/m)
Silver (Conductor)	6.30 × 107
Copper	5.96 × 107
Gold	4.10 × 107
Aluminum	3.50 × 107
Platinum	9.43 ×106
Graphite	2.00 × 105 - 3.00 × 105
Iron	1.00 × 107
Stainless Steel	1.45 × 106
Silicon (Semiconductor)	1.56 × 10-3
Glass (Insulator)	10-11 – 10-15
Rubber (Insulator)	10-14
Carbon Diamond (Insulator)	10-13

Factors Affecting Electrical Conductivity

The electrical conductivity of a material majorly depends on the following factors −

• Nature of material − From the above table, it is clear that the electrical conductivity of different material is different depending on the nature of the material. For example, Silve is a conductor, hence its conductivity is very high, whereas glass is an insulator and having very low electrical conductivity.

• Temperature − When temperature of a material changes, it affects the number of free electrons in the material and hence affects the conductivity. For example, if we increase the temperature of silicon, then its conductivity increases.

Applications of Electrical Conductivity

Electrical conductivity is one of the important parameters while selecting a material for a specific electrical application. Here are some practices in the field of electrical and electronics engineering that shows the importance of electrical conductivity.

Electric Power Transmission and Distribution

Electrical conductivity is the primary concept considered while selecting a material to design the transmission and distribution systems. It is a usual practice that materials having higher electrical conductivity are used for electric power transmission and distribution. The higher electrical conductivity of the transmission and distribution conductors and wires ensures minimal energy loss during power transmission between power plants to grids and utilization points.

Electrical and Electronic Circuits

Electrical conductivity is also used to decide the material used for designing the parts of electric and electronic circuits. For example, materials that have high electrical conductivity are used to make the conducting parts of the circuit, whereas materials with lower electrical conductivity are used to provide insulation in the circuit.

Communication Systems

Electrical conductivity is also used to select appropriate materials for designing different components of a communication system. As communication system deals with low power signals, hence it is important to select a material of desired electrical conductivity for improved efficiency of the system.

Batteries

A battery requires materials of different electrical conductivity. For example, electrodes of the battery must have high electrical conductivity, while the casing of the battery must have lower electrical conductivity. Hence, designing a battery also requires the knowledge of electrical conductivity of materials.

Conclusion

In conclusion, electrical conductivity is the property of material allowing current flowing through a material easily. It has a principle based on the ease in the movement of electrons. It depends on the nature of the material. Hence, different materials have different electrical conductivity. Electric conductivity is high for conductor materials and it low for semiconductors and insulators.

Electrical conductivity is one of the crucial concepts in electrical engineering that allows us to classify electrical materials in different categories. Also, it is useful in selecting a best material for a specific application. For example, to design a transmission conductor, a material with high electrical conductivity is used. To design the insulation shoes, a material with low electrical conductivity is used.