Otis Singleton
Conductors are materials that allow electricity to flow through them in more than one direction with little resistance. The property of conductors to conduct electricity is called conductivity. Materials with good mobility of electrons are known as conductors, and materials with less mobility of electrons are referred to as insulators. The best electrical conductor under ordinary temperature and pressure conditions is the metallic element silver, closely followed by copper, iron, and steel. However, silver is not always an ideal choice as a conductor due to its expense and susceptibility to tarnishing, an oxide layer that forms on the surface of the metal, which is not conductive. Other good conductors include concrete, pure water, and aluminum.
| Characteristics | Values |
|---|---|
| Material type | Metals, electrolytes, superconductors, semiconductors, plasmas, non-metallic conductors (e.g. graphite, conductive polymers, concrete), and certain liquids (e.g. saltwater) |
| Electron movement | Materials with high electron mobility are good conductors. |
| Temperature | Increasing temperature reduces conductivity. |
| Impurities | Materials with impurities may become conductors. For example, pure water is an insulator, but saltwater conducts due to free-floating ions. |
| Shape and size | Thicker pieces of material conduct better than thinner pieces. Shorter pieces of the same thickness conduct better than longer pieces. |
| Resistivity | Resistivity is a measure of a material's ability to oppose electric current. |
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Metals
Electrical conductivity depends on electron movement because protons and neutrons don't move—they are bound to other protons and neutrons in atomic nuclei. In addition to the type of material, factors such as the size and temperature of the material also affect conductivity. Metals are good conductors when cool and less efficient when hot.
Valence electrons are attracted to their atoms but can easily be knocked out of place and carry electric currents. Inorganic substances like metals and plasmas readily lose and gain electrons, making them top conductors.
The best electrical conductor, under ordinary temperature and pressure, is the metallic element silver. However, silver is not always an ideal choice as a material because it is expensive and susceptible to tarnishing, and the oxide layer known as tarnish is not conductive. Copper is also a good conductor and is the international standard to which other electrical conductors are compared.
Aluminum wire is the most common metal in electric power transmission and distribution. It is used because of its low density and cost-effectiveness, but it has disadvantages such as its tendency to form an insulating oxide and "creep", which causes connections to loosen.
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Electrolytes
An example of an electrolyte is saltwater, which conducts electricity easily. Salt consists of sodium (positively charged) and chlorine (negatively charged), and when combined, their charges balance each other out. Atoms with an electrical charge are called ions. When dissolved in a liquid, that liquid can then conduct electricity.
Solid-state electrolytes also exist, and in medicine, the term electrolyte refers to the substance that is dissolved. Electrically, such a solution is neutral. If an electric potential is applied to such a solution, the cations of the solution are drawn to the electrode with an abundance of electrons, while the anions are drawn to the electrode with a deficit of electrons. The movement of anions and cations in opposite directions within the solution amounts to a current.
Conductivity cells are tools used to measure the strength of an electrolyte solution to conduct electricity. Electrolyte drinks are used to replenish the body's water and electrolyte concentrations after dehydration caused by exercise, excessive alcohol consumption, heavy sweating, diarrhoea, vomiting, starvation, etc.
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Superconductors
Superconductivity is a set of physical properties observed in certain materials, known as superconductors, where electrical resistance vanishes and magnetic fields are expelled from the material. Superconductivity was discovered in 1911 by Dutch physicist Heike Kamerlingh Onnes, who was studying the resistance of solid mercury at cryogenic temperatures.
Unlike ordinary metallic conductors, whose resistance decreases gradually as their temperature is lowered, superconductors have a critical temperature below which the resistance drops abruptly to zero. This critical temperature varies for different materials. For example, some cuprate-perovskite ceramic materials have a critical temperature above 35 K (-238 °C), while others, such as YBCO, have a critical temperature of 92 K (-181 °C). The critical temperature of a superconductor depends on the isotopic mass of its constituent element.
At extremely low temperatures, metals conduct electricity better than any known substance at room temperature. This phenomenon is called superconductivity. A superconductor can support very high electrical currents due to its lack of electrical resistance. However, above a "critical current", the electron pairs break up and superconductivity is destroyed.
In 2025, MIT physicists discovered a new type of superconductor that also exhibits magnetic properties. This "chiral superconductor" was found in rhombohedral graphene, which is made from atomically thin, lattice-like sheets of carbon atoms. When these sheets are cooled to extremely low temperatures, the material becomes a superconductor, allowing any electrical current to flow through without resistance. This discovery challenges the traditional belief that magnets and superconductors cannot coexist.
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Semiconductors
The conductivity of a semiconductor can be modified by doping and by the application of electrical fields or light. Doping involves adding impurities to the crystal structure to give them their useful electrical properties. When doped with a material with an extra valence electron, it gives an overall negative charge and is called an N-type semiconductor. When doped with a material that is missing one valence electron, it gives an overall positive charge, and these areas where an electron is needed are called electron holes, known as P-type doping.
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Non-metallic conductors
While metals are the most common electrical conductors, some non-metallic materials can also conduct electricity. These are known as non-metallic conductors.
Graphite, for instance, is a non-metal that can conduct electricity. It is a form of carbon that possesses a delocalized sea of electrons, which gives them the mobility to collide and generate an electric current. Another form of carbon, diamond, is an insulator, demonstrating that the atomic structure of a non-metal is crucial in determining its conductivity.
Conductive polymers are another example of non-metallic conductors. These synthetic materials are created by altering the atomic structure of hydrocarbons, which normally cannot conduct electricity due to their covalent bonds. By manipulating the structure of these bonds, conductive polymers can be designed to have free electrons, allowing them to conduct electricity.
Certain organic ionic liquids can also conduct electricity. For example, pure water is a non-conductor, but when ionic impurities like salt are introduced, it can rapidly become a conductor.
While not a true non-metallic conductor, silicon is a semiconductor that can act as a conductor under certain conditions. At room temperature, silicon has poor conductivity, but at extremely low temperatures, it can become a superconductor, exhibiting almost zero resistance to the flow of electric current.
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Frequently asked questions
A conductor is a material that allows electricity to flow through it in more than one direction with little resistance.
Metals are the best conductors of electricity, as they have lots of free electrons and promote mobility. The best electrical conductor is silver, followed by copper, iron, and steel. Other good conductors include aluminium, concrete, graphite, and saltwater.
A resistor is a material that conducts electricity fairly well but not as good as a conductor. The most common example of a resistor is a combination of carbon and clay, mixed in a specific ratio to produce a constant, predictable opposition to the electric current.
Insulators are non-conducting materials with few mobile charges that support only insignificant electric currents. Examples of insulators include glass, plastic, and pure water.
