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Conductivity refers to the ability of a material to transmit energy. There are different types of conductivity, including electrical, thermal, and acoustical conductivity. The most electrically conductive element is silver, followed by copper and gold. Silver also has the highest thermal conductivity of any element and the highest light reflectance. Although it is the best conductor, copper and gold are used more often in electrical applications because copper is less expensive and gold has a much higher corrosion resistance. Because silver tarnishes, it is less desirable for high frequencies because the exterior surface becomes less conductive.
As to why silver is the best conductor, the answer is that its electrons are freer to move than those of the other elements. This has to do with its valence and crystal structure.
Most metals conduct electricity. Other elements with high electrical conductivity, are aluminum, zinc, nickel, iron, and platinum. Brass and bronze are electrically conductive alloys, rather than elements.
Table of the Conductive Order of Metals
This list of electric conductivity includes alloys as well as pure elements. Because the size and shape of a substance affect its conductivity, the list assumes all samples are the same size. In order of most conductive to least conductive:
- Carbon Steel
- Stainless Steel
Factors That Affect Electrical Conductivity
Certain factors can affect how well a material conducts electricity.
- Temperature: Changing temperature of silver or any other conductor alters its conductivity. In general, increasing the temperature causes thermal excitation of the atoms and decreases conductivity while increasing resistivity. The relationship is linear, but it breaks down at low temperatures.
- Impurities: Adding an impurity to a conductor decreases its conductivity. For example, sterling silver is not as good of a conductor as pure silver. Oxidized silver is not as good a conductor as untarnished silver. Impurities hinder electron flow.
- Crystal structure and phases: If there are different phases of a material, conductivity will slow slightly at the interface and may be different from one structure than another. The way a material has been processed can affect how well it conducts electricity.
- Electromagnetic fields: Conductors generate their own electromagnetic fields when electricity runs through them, with the magnetic field perpendicular to the electric field. External electromagnetic fields can produce magnetoresistance, which can slow the flow of current.
- Frequency: The number of oscillation cycles an alternating electrical current completes per second is its frequency in Hertz. Above a certain level, a high frequency can cause current to flow around a conductor rather than through it (skin effect). Since there is no oscillation and hence no frequency, the skin effect does not occur with direct current.