Beatrice Lang
Whether a substance conducts electricity or not is determined by its physical and chemical properties. Materials with electrically charged particles that are free to move inside them are known as conductors, while those that do not allow the flow of electricity are known as insulators or dielectrics. Metals are the most common conductors of electricity due to their high electron mobility, while organic molecules are typically insulators due to their stable covalent bonds. However, the distinction between conductors and insulators is not always clear-cut, and most materials fall somewhere in the middle of the spectrum.
| Characteristics | Values |
|---|---|
| Definition | A conductor is a substance or material that allows electricity to flow through it. |
| Charge carriers | Usually electrons or charged ions. |
| Electron movement | Electrons move easily from atom to atom when voltage is applied. |
| Resistance | Conductors have low resistance. |
| Electric field | Conductors have no electric field inside, which permits the movement of electrons or ions. |
| Charge density | Conductors have a zero charge density, ensuring that positive and negative charges cancel each other out. |
| Potential | Both ends of a conductor are at the same potential. |
| Current flow | Electricity flows through a conductor when the potential is changed at one end, allowing electrons to flow from one end to the other. |
| Energy band theory | For a material to conduct electricity, there must be no energy gap between its valence band and conduction band. |
| Examples | Silver, copper, gold, aluminium, graphite, saltwater. |
| Comparison with insulators | Insulators do not allow electrical current to pass through them and are often used to coat or provide a barrier between conductors. |
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What You'll Learn
Metals as good conductors
Metals are considered good conductors of electricity due to the presence of valence electrons, also known as "free electrons". These free electrons are not bound to the atoms of the metal and can move freely, allowing for the flow of electric charge. The high mobility of electrons in metals is due to their unique atomic structure, where electrons can move to higher energy levels within their orbitals to transfer energy. This is in contrast to insulators, which have a full valence shell that prevents the movement of electrons.
Silver is widely recognised as the best conductor of electricity among pure elements. It has a high number of movable atoms (free electrons) that facilitate the flow of electric charge. Copper is another excellent conductor, commonly used in household appliances and metal wiring. It is less conductive than silver but offers a more economical option for everyday use.
Other metals that are good conductors include gold, zinc, nickel, and lead. Gold is notable for its resistance to tarnishing when exposed to air, but its high cost limits its usage to specific applications. Zinc becomes malleable at 100 °C, making it easy to shape without breaking. Nickel exhibits high electrical conductivity, while lead is commonly used in electrical contacts due to its softness and ability to deform easily, creating solid connections.
While aluminium can conduct electricity, it is not as effective as other metals due to its tendency to form an insulating oxide layer. However, it is widely used in high-voltage transmission lines due to its cost-effectiveness and mechanical properties. The choice of metal as a conductor depends on various factors, including cost, availability, and the specific requirements of the application.
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Free movement of electrons
Whether a material is a good conductor of electricity is determined by its physical and chemical properties. Conductivity is determined by the types of atoms in a material and how they are linked together. Materials with high electron mobility (many free electrons) are called conductors, while materials with low electron mobility (few or no free electrons) are called insulators.
Free electrons are formed with low kinetic energy and they simply diffuse through the gas, taking part in the random thermal motion of all the atoms. These free electrons can also be formed with enough kinetic energy to cause additional excitation and ionization. When an electron moves away from a covalent bond, there is an electron deficiency in that bond. This deficiency may be filled by one of the neighbouring electrons, which results in a shift of the deficiency location.
In metals, the particles are held together by strong metallic bonds. The particles are close together and in a regular arrangement. Metal atoms have loose electrons in the outer shells, which form a 'sea' of delocalized or free negative charge around the close-packed positive ions. These loose electrons are called free electrons. They can move freely throughout the metallic structure.
The normal motion of "free" electrons in a conductor is random, with no particular direction or speed. However, electrons can be influenced to move in a coordinated fashion. As each electron moves uniformly through a conductor, it pushes on the one ahead of it, such that all the electrons move together as a group. This momentum transfer model makes metal an ideal choice for a conductor.
Silver is the best conductor in the “conductors” list, offering easier passage for electrons than any other material. Dirty water and concrete are also listed as conductors, but they are substantially less conductive than any metal.
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Insulators and dielectric materials
Insulators are non-conducting materials with few mobile charges that support only insignificant electric currents. They have low electrical conductivity and strongly bonded molecules. Examples of insulators include cotton, plastic, and rubber.
Dielectric materials, on the other hand, are electrical insulators that can be polarised by an applied electric field. They have no loosely bound or free electrons that may drift through the material. Instead, the charges shift slightly from their average equilibrium positions, causing dielectric polarisation. This means that positive charges are displaced in the direction of the field, while negative charges shift in the opposite direction. Dielectric materials have high resistivity and a strong attraction between their electrons and the parent nucleus. They are commonly used in capacitors to store energy and as cooling agents in transformers. Dielectric materials can be solids, liquids, or gases, with solids being the most commonly used in electrical engineering. Examples of solid dielectrics include porcelain, glass, and plastics.
The terms "insulator" and "dielectric" are often confused. While an insulator indicates electrical obstruction, a dielectric indicates the ability of a material to store energy through polarisation. The dielectric constant, or relative permittivity, measures the storing capacity of a material. A larger dielectric constant leads to greater charge storage and capacitance. Dielectric materials used for capacitors are chosen to be resistant to ionisation, allowing them to operate at higher voltages.
In summary, insulators and dielectric materials both play important roles in electrical systems. Insulators block electric charges, while dielectrics store them and can be polarised by an electric field. Dielectrics are particularly useful in capacitors and transformers due to their energy-storing capabilities.
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Temperature effects on conductivity
Temperature has a significant effect on the conductivity of materials. This effect is observed in solutions, metals, and semiconductors.
In solutions, an increase in temperature leads to a decrease in viscosity and an increase in ion mobility and concentration. This change in the nature of ions directly affects the conductivity of the solution, with higher temperatures resulting in higher conductivity.
Metals, as conductors, are characterized by their delocalized electrons, which can move freely and collide, facilitating the flow of electric charge. When the temperature increases, the positive ions in the metal conductor vibrate more, and the electrons gain energy, moving into higher energy levels. This increase in thermal speed of the electrons results in an increase in resistance and a decrease in metal conductivity.
In contrast, semiconductors exhibit an increase in electrical conductivity with increasing temperature. This is because the electrons can jump from the valence band to the conduction band in the semiconductor as the temperature rises.
The effect of temperature on conductivity is quantified by the Temperature Coefficient of Variation, which expresses the rate of change in a solution's conductivity with temperature increase as a percentage.
Additionally, temperature can cause materials to expand or contract, altering their geometry and resistance characteristics. This effect is governed by the material's thermal expansion coefficient and is generally small. An increase in temperature also generates more phonons, which are lattice vibrations that disrupt the path of electrons, leading to reduced electron collisions and decreased current transfer.
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Silver as the best conductor
A conductor is a material that allows the flow of electric charge or current. Metals are common electrical conductors due to their sea of delocalized electrons, which gives them the mobility to collide and transfer momentum.
Silver is widely considered the best conductor of electricity among all elements. Its high electrical conductivity is attributed to its atomic structure. Silver, with an atomic number of 47, has a single valence electron in the outermost 5s orbital that is not tightly bound to the nucleus. This loose binding allows silver atoms to easily transfer valence electrons, which is essential for conducting electricity.
The high mobility of electrons in silver means that electric current can pass through it with minimal resistance. This property of silver is further enhanced by its crystal structure, which synergizes with its atomic structure to make it an even more effective conductor.
While other metals like copper and gold are also highly conductive, silver outperforms them due to its unique atomic and crystal structures. Copper, for example, is more widely used due to its abundance and lower cost, but it has slightly lower conductivity than silver. Gold, meanwhile, is often chosen for specialized electronic equipment requiring corrosion resistance, but silver remains the top choice for pure conductive efficiency.
It is important to note that the conductivity of silver can be affected by factors such as temperature and impurities. Increasing the temperature of silver generally decreases its conductivity, while adding impurities, such as in sterling silver, reduces its effectiveness as a conductor compared to pure silver.
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Frequently asked questions
A conductor is a substance or material that allows electricity to flow through it.
Metals are the most common conductors due to their high number of free electrons. Some of the best metal conductors are silver, copper, and gold. There are also non-metallic conductors, such as graphite, conductive polymers, and liquids.
Conductors have low resistance to the flow of electric charge, allowing electricity to pass through them easily. This is due to the free movement of electrons through the material.
Insulators, or dielectric materials, do not allow electrical current to pass through them. They often have a molecular structure that impedes electron movement. Examples of insulators include glass, plastic, and rubber.
In addition to the type of material, the size and temperature of a material can also affect its conductivity. For example, a thick piece of matter will conduct better than a thin piece of the same size and length.
