Molly Ayala
Conductivity is a physical property of a substance. A physical property of a substance is anything that can be observed or measured without changing its identity. Electrical conductivity is the ability of a substance to conduct electricity. This is influenced by the substance's atomic structure, temperature, impurities, and external factors. A substance that conducts electricity is called a conductor, and it must have free electrons or ions that can carry an electric current when an electric field is applied. The opposite of a conductor is an insulator, which has very few or no free electrons or ions and does not allow an electric current to flow through it.
| Characteristics | Values |
|---|---|
| Definition | A conductor of electricity is a material that readily allows the flow of electricity due to the presence of free electrons or ions |
| Types | Metallic, ionic, molecular, superconductors |
| Examples | Silver, copper, gold, aluminium, graphite |
| Applications | Wiring, transmission lines, electrical machines, heating elements, electrostatic shielding |
| Properties | Low resistivity and resistance, zero internal electric field, surface charge distribution |
| Inductance | Measure of how much a conductor opposes the change in electric current flowing through it |
| Resistance | Measure of how much a conductor opposes the flow of electric current |
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What You'll Learn
Metals as good conductors
The ability of a material to conduct electricity is a physical property. Conductivity is the property of conductors that allows them to "conduct" electricity. Conductors offer less resistance to the flow of charges, allowing for an easy charge transfer. Metals are good conductors of electricity because they have free electrons that facilitate the transfer of charge from one point to another.
Metals have a high number of free electrons that can move freely through the material, allowing for an easy flow of electric current. These free electrons are not bound to any specific atom, and they form a "'sea'" of electrons around the positively charged atomic nuclei. This "sea" of electrons allows for the efficient transfer of electrical current. The more free electrons present in a metal, the greater its conductivity. Silver, for example, has the highest electrical conductivity among pure elements, followed by copper and gold.
The atoms in metals form a matrix, or a crystal lattice, through which their outer electrons can move freely. This electron mobility is what makes metals good conductors. In metallic bonds, valence electrons are not associated with a particular atom or pair of atoms but can move freely within the lattice. This free movement of electrons is what allows metals to conduct electricity effectively.
Metals are commonly used as conducting materials in practical applications. For instance, the wires in your house are likely made of copper, and electric plugs and irons also typically contain metal conductors. Metals are used in these applications because they have a high number of free electrons and promote mobility, making them excellent conductors of electricity.
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Free movement of electrons
The ability of a material to conduct electricity is a physical property. Some materials have electrically charged particles called electrons that are free to move inside them. This movement of electrons is what we call electricity or electric current. When these materials are connected to a battery or a cell, the free electrons start to move and allow electricity to pass through them. This ability of materials to pass electricity through them is known as conductivity. Materials with good mobility of electrons are called conductors, and those with less mobility of electrons are called insulators.
The free movement of electrons through a conductor is a useful visualisation for understanding how current passes through it. However, this movement is difficult to observe directly, especially when taking a quantum mechanical approach that accounts for the uncertainty of position and momentum. Instead, one can use simplified quantum mechanical models to visualise the corresponding solutions to the problem at hand. For example, in the band theory of solids, the electrons you call "free" are in the conduction band, while the rest are bound to lattice locations.
In classical calculations, free electrons are visualised as having random motion or random distribution through the conductor. When an electric field is applied, a small drift velocity is induced in the electrons, moving in the opposite direction to the field through the wire. This drift velocity is orders of magnitude smaller than the speed of the electric current, like turning on a bulb.
The more free electrons present in a metal, the greater its conductivity. Silver is the best electrical conductor among pure elements, followed by copper and gold. However, since silver is expensive, copper is commonly used in household appliances and circuits. Aluminium is also a good conductor, slightly less conductive than copper, and is often used in combination with it. Some non-metals are excellent conductors, such as carbon in the form of graphite, where one electron is left free for bonding.
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Conductivity
Metals are closely packed atoms with free-moving valence electrons, making them good conductors. Materials with good mobility of electrons are known as conductors, and materials with less mobility of electrons are referred to as insulators. Conductors have low resistivity and resistance, while insulators have high resistivity and resistance. Resistance is the measure of how much a conductor opposes the flow of electric current, and it depends on the material's resistivity, length, cross-sectional area, and temperature.
Some non-metals are also excellent electrical conductors. For example, carbon in the form of graphite is a good conductor because only three of the four carbon atoms are used for bonding, leaving one electron free for bonding. However, most non-metals are poor conductors of electricity.
Superconductors are elements or metallic alloys that, when cooled below a certain threshold temperature, lose electrical resistance and become superconductors. Some of the best superconductors are niobium, cuprate, magnesium, and diboride.
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Superconductors
The phenomenon of superconductivity was discovered in 1911 by Dutch physicist Heike Kamerlingh Onnes, who was studying the resistance of solid mercury at cryogenic temperatures. Mercury was the first material discovered to exhibit superconductivity, but many other materials have since been found, including metals and alloys of niobium and titanium.
Another property of superconductors is the Meissner effect, where they expel magnetic fields from their interior when they transition into the superconducting state. This phenomenon allows for applications such as magnetic levitation, where a superconductor can levitate above a magnet due to the interaction between the expelled magnetic fields.
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Insulators
The efficacy of an insulator is measured in terms of its thermal resistance, or R-value. The higher the R-value, the better the insulator. Insulators with high resistivity are very good electrical insulators. Glass, paper, and PTFE are examples of materials with high resistivity. A larger class of materials with lower bulk resistivity can still be used as insulation for electrical wiring and cables. Examples include rubber-like polymers and most plastics.
Glass insulators were first produced in the 1850s for use with telegraph lines. As technology developed, insulators were needed for telephone lines, electric power lines, and other applications. Today, glass insulators are collected as antiques, with over 3,000 collectors worldwide.
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Frequently asked questions
Yes, being a conductor of electricity is a physical property. The ability of a material to conduct electricity is called electrical conductivity, and it does not change the identity of the substance.
Conductivity is the property of a substance that allows electrons or heat to pass through it.
A good electrical conductor is a material that has free electrons or ions that can carry an electric current when an electric field is applied. Metals are good electrical conductors due to their closely packed atomic structure and free-moving electrons.
Copper is a good electrical conductor. Although oxygen-free copper has higher electrical conductivity than regular copper due to the disruption of electron flow by oxygen atoms.
An insulator is the opposite of a conductor. It has very few or no free electrons or ions and does not allow an electric current to flow through it.
