Materials that allow the flow of charge (current) or thermal energy through it with less resistance are considered good conductors and conductivity is the measure of the ability of a conducting material through which an electron or electric charge or heat can flow through it.
Conducting materials are classified as conductors, insulators, and semiconductors. Metals fall in the category of conductors which is the most conductive element and insulators (wood, ceramics, plastics) are the least conductive, whereas semiconductors are the materials having a negative temperature coefficient (they tend to increase their conductivity at higher temperatures), whereas metals have a positive temperature coefficient (their conductivity is decreased at higher temperatures due to collision of electrons resulting in the increase of resistance).
Electrical conductivity tells us how well a material will allow electricity to travel through it. Most people think of copper wires have great electrical conductivity but they are not correct we have many other metals having more conductivity than copper.
Electrical conductivity is denoted by the symbol: σ (sigma)
Conductive metals serve two primary phenomena:
Electric conductivity—It is the measure of the amount of electrical current a material can carry in other words, it is the ability to carry a current. Electrical conductivity is also known as specific conductance. It is the reciprocal of electric resistivity. Conductivity is an intrinsic property of a material.
Thermal conductivity—It is a property of conducting material that describes the ability of a material to conduct or transfer heat. More specifically thermal conductivity can be defined as “the quantity of heat transmitted through a unit thickness of a material in a direction normal to a surface of the unit area – due to a unit temperature gradient in the steady state”.
Heat can only be transferred through these three means: conduction, convection, and radiation. In addition, conduction is perhaps the most common means of heat transfer and occurs regularly in nature. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal conductivity.
Note: Generally, metals having high electrical conductivity also have high thermal conductivity.
The most conducting metals on Earth
Silver is the most conductive of all metals. If we compare silver, copper, and gold on a scale of 0 to 100, silver ranks 100, with copper at 97 and gold at 76.
- Silver – It has the highest electrical conductivity of all metals. This is because silver only has one valence electron. In addition, this single electron is free to move around with little resistance. Its conductivity (σ) is 6.30×107.
- Copper – The second most conductive metal on earth. Other than electrical conductivity it is widely used for its good thermal conductivity in coating high-end cookware and kitchen appliances for commercial applications. Its conductivity (σ) is 5.96×107.
- Gold – Gold occupies the third most conductive metal on earth. It provides resistance against corrosion or getting or tarnish unlike other highly conductive metals such as copper and silver. It is a very soft and pliable material, which can be easily drawn out into narrow wires or plated into thin coatings. Gold has played an important role in the electronics sector for decades. It is used in making connectors, switch and relay contacts, connecting wires, and connection strips. Its conductivity (σ) is 4.11×107.
- Aluminum – It has a low density so it is a lightweight metal and also has high resistance to corrosion, this makes this metal perfect for the aeronautic and communication industries. This is the reason it is widely used in the long-distance supply of electricity. Its conductivity (σ) is 3.77×107.
- Zinc – It is a moderately good conductor of electricity. At room temperature, zinc is brittle (hard but easily broken), but it becomes malleable at 100 C. Which means it can be bent and shaped without breaking. Zinc is much less conductive than the upper four counter members. Its conductivity (σ) is 1.69×107
Note: The values of electrical conductivity are compared at 20 °C/ 68 °F/ 293 K (S/m)
Decreasing order of conductivity of metals
Silver>Copper>Gold>Aluminum>Zinc>Nickel>Brass>Bronze>Iron>Platinum>Carbon Steel>Lead>Stainless Steel
Why silver is the best conductor of electricity?
The reason behind silver being the most conductive metal is its electronic configuration (configuration of electrons), such as 2, 8, 18, 18, and 1 electron per shell. This configuration tells that the last shell has only one electron loosely bonded to the nucleus.
This valence electron in silver helps to contribute to the electrical conductivity by being in the conduction band. Besides, the larger size of the silver atom creates a lesser influence of the nucleus over the electrons, thus making it more suitable for the conduction of electricity and heat than any other element.
Metals like silver and copper are a few of the metals with this particular characteristic. That is the reason why they are great electric and thermal conductors.
Using silver for the conduction of electricity will be the best, but silver is a highly costly metal than copper so silver has very few electrical applications in use it is often used for solder, electrical contacts, and printed circuit boards. Copper is cost-effective so it is widely used for conduction all over the world.