Classification of materials in relation to the ability to conduct electric current. The most electrically conductive metal in the world

Conductors of electric current can be completely different substances. For example, both a piece of metal wire and sea water are electrical conductors. But the electric current in them is different in nature. Therefore, they are divided into two groups:

• the first kind with conductivity based on electrons;
• of the second kind with ion-based conductivity.

Electrical conductors of the first kind are all metals and carbon. Representatives of the second kind are acids, alkalis, solutions and molten salts, which are called "electrolytes".

• The current in the conductors flows at any voltage and is directly proportional to the voltage.

The best electrical conductors normal conditions are silver, gold, copper and aluminum. Copper and aluminum are the most widely used for making various wires and cables due to their lower cost. Mercury is a good liquid conductor of the first kind. Conducts well electricity and carbon. But due to the lack of flexibility, its application is impossible. However, graphene, a relatively recent form of carbon, makes it possible to make threads and cords from threads.

But graphene cords have a resistance that is unacceptably high for conductors. Therefore, they are used in electric heaters. In this capacity, the graphene cord is superior to metal wire counterparts based on nickel-chromium alloy, since it can provide a higher temperature. Tungsten wire conductors are used in a similar way. Spirals of incandescent lamps and electrodes of gas-discharge lamps are made of them. Tungsten is the most refractory electrical conductor.

Processes in conductors

An electric current flowing in a conductor has certain effects on it. Either way, the temperature rises. But it is also possible chemical reactions, which lead to changes in physical and chemical properties. Biggest change electrical conductors of the second kind are susceptible. The electric current in them causes an electrochemical reaction called electrolysis.

As a result, the ions of the conductor of the second kind receive the necessary charges near the electric poles and are restored to the state that was before the appearance of acid, alkali or salt. Electrolysis is widely used to obtain many pure chemicals from natural raw materials. Pure aluminum and some other metals are obtained by electrolysis of melts.

Conductors of the first and second kind can not only conduct electric current when an external voltage is applied to them. When interacting, for example, lead with an acid, that is, a conductor of the first kind with a conductor of the second kind, an electrochemical reaction occurs that ensures the release electrical energy. The device of accumulators is based on it.

Electric conductors of the first kind can also change when in contact with each other. For example, the contact of a copper and aluminum conductor is a poor solution without a special coating of it. Air humidity is sufficient for destruction at the point of contact by an electrochemical reaction. Therefore, it is recommended to protect such connections with varnish or similar substances.

For some conductors of the first kind, with significant cooling, a special state arises, being in which they do not offer resistance to electric current. This phenomenon is called superconductivity. Classical superconductivity corresponds to a temperature close to that of liquid helium. However, as research progressed, new superconductors with higher temperatures were discovered.

• The economically justified use of superconductivity is one of the priority goals of modern energy.

Electric current can flow not only in conductors of the first and second kind. There are also semiconductors and gases that also conduct electricity. But that's a completely different story...

electrical conductor

electrical wire

Conductor- a substance that conducts electricity. Among the most common solid conductors are known metals, semimetals. An example of conductive liquids is electrolytes. An example of conducting gases is an ionized gas (plasma). Under normal conditions, some substances that are insulators under external influences can become conductive, namely, the conductivity of semiconductors can vary greatly with changes in temperature, illumination, doping, etc.

Conductors are also called parts of electrical circuits - connecting wires and tires.

The microscopic description of conductors is connected with the electronic theory of metals. Most simple model The description of conductivity has been known since the beginning of the last century and was developed by Drude.

Conductors are of the first and second kind. Conductors of the first kind include those conductors in which there is electronic conductivity (through the movement of electrons). Conductors of the second kind include conductors with ionic conductivity (electrolytes)

see also

• Polyaniline - polymer with electronic conductivity

Literature

• Jean M. Rabai, Ananta Chandrakasan, Borivoj Nikolic 4. Explorer// Digital Integrated Circuits. Design Methodology = Digital Integrated Circuits. - 2nd ed. - M.: "Williams", 2007. - S. 912. - ISBN 0-13-090996-3

Wikimedia Foundation. 2010 .

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electrical conductor- elektros laidininkas statusas T sritis fizika atitikmenys: engl. conductor of electricity vok. electrischer Leiter, m rus. electrical conductor, m pranc. conducteur electrique, m … Fizikos terminų žodynas

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Each person, constantly using electrical appliances, is faced with the properties of electrical conductivity, namely:

All substances, depending on the electrical conductivity, are divided into conductors, semiconductors and dielectrics:

1. conductors - which pass an electric current;

2. dielectrics - have insulating properties;

3. semiconductors - combine the characteristics of the first two types of substances and change them depending on the applied control signal.

TO conductors include those substances that have in their structure a large number of free, rather than bound electric charges that can start moving under the influence of an applied external force. They can be in solid, liquid or gaseous state. The most excellent conductors of electric current are metals. R Solutions of salts and acids, moist soil, the bodies of people and animals are also good conductors of electrical charges.

If you take two conductors, between which a potential difference is formed, and connect a metal wire inside them, then an electric current will flow through it. Its carriers will be free electrons, not held by the bonds of atoms. They characterize the magnitude of electrical conductivity or the ability of any substance to pass through itself electric charges - current.

The value of electrical conductivity is inversely proportional to the resistance of the substance and is measured by the appropriate unit: Siemens (Sm).

1 cm=1/1 ohm.

In nature, charge carriers can be:

electrons;

ions;

holes.

According to this principle, electrical conductivity is divided into:

electronic;

ionic;

hole.

The quality of the conductor makes it possible to evaluate the dependence of the current flowing in it on the value of the applied voltage. It is customary to call it by the designation of the units of measurement of these electrical quantities - the current-voltage characteristic.

Conductors with electronic conductivity (conductors of the 1st kind)

The most common representatives of this type are metals. They create an electric current solely due to the movement of the flow of electrons.

When an electric current passes through metal conductors, neither their mass nor their chemical composition. Therefore, metal atoms do not participate in the transfer of electric charges. Studies of the nature of the electric current in metals have shown that the transfer of electric charges in them is carried out only by electrons.

Inside metals, they are in two states:

bound by the forces of atomic cohesion;

free.

Electrons held in orbit by the forces of attraction of the atomic nucleus, as a rule, do not participate in the creation of electric current under the action of external electromotive forces. Free particles behave differently.

If an EMF is not applied to a metal conductor, then free electrons move randomly, randomly, in any direction. Their movement is due to thermal energy. It is characterized by different speeds and directions of movement of each particle at any given time.

When the energy of an external field with a strength E is applied to the conductor, then a force directed opposite to the acting field acts on all the electrons together and each separately. It creates a strictly oriented movement of electrons, or in other words, an electric current.

The current-voltage characteristic of metals is a straight line that fits into Ohm's law for a section and a complete circuit.

In addition to pure metals, other substances also have electronic conductivity. These include:

alloys;

individual modifications of carbon (graphite, coal).

All of the above substances, including metals, are classified as conductors of the 1st kind. Their electrical conductivity is in no way connected with the transfer of the mass of a substance due to the passage of an electric current, but is determined only by the movement of electrons.

If metals and alloys are placed in a medium of ultralow temperatures, they pass into a state of superconductivity.

Conductors with ionic conductivity (conductors of the 2nd kind)

This class includes substances in which an electric current is created due to the movement of charges by ions. They are classified as conductors of the second kind.

solutions of alkalis, acids, salts;

melts of various ionic compounds;

various gases and vapours.

Electric current in liquid

Conducting electric current liquid media in which electrolysis occurs - the transfer of a substance along with charges and its deposition on the electrodes, is commonly called electrolytes, and the process itself is called electrolysis.

It occurs under the influence of an external energy field by applying a positive potential to the anode electrode and a negative one to the cathode.

Ions inside liquids are formed due to the phenomenon of electrolytic dissociation, which consists in the splitting of a part of the molecules of a substance that have neutral properties.

Under the action of the applied voltage to the electrolyte, the cations begin to move strictly towards the cathode, and the anions - towards the anode. In this way, chemically pure copper without impurities is obtained, which is released at the cathode.

In addition to liquids, there are also solid electrolytes in nature. They are called superionic conductors(super-ionics), having a crystal structure and ionic nature chemical bonds, causing high electrical conductivity due to the movement of ions of the same type.

Conductors with hole conductivity

These include:

germanium;

selenium;

silicon;

compounds of individual metals with tellurium, sulfur, selenium and some organic substances.

They got the name semiconductors and belong to group No. 1, that is, they do not form the transfer of matter during the flow of charges. To increase the concentration of free electrons inside them, it is necessary to spend additional energy on detaching bound electrons. It is called ionization energy.

An electron-hole transition operates in the composition of a semiconductor. Due to its semiconductor passes current in one direction and blocks in the opposite direction when an opposite external field is applied to it.

semiconductor structure

Conductivity in semiconductors is:

1. own;

2. impurity.

The first type is inherent in structures in which charge carriers appear in the process of ionization of atoms of their substance: holes and electrons. Their concentration is mutually balanced.

Conductors, dielectrics and electron flow

Electrons various types atoms have different degrees of freedom of movement. In some materials, such as metals, the outer electrons of atoms are so weakly bound to the nucleus that they can easily leave their orbits and move randomly in the space between neighboring atoms, even attemperature. These electrons are often called free electrons.

In other types of materials, such as glass, the electrons in atoms have very little freedom of movement.I am. However, external forces, such as physical friction, may cause some of these electrons to leave their own atoms and go to the atoms of another material, but they cannot move freely between the atoms of the material.

This relative mobility of electrons in a material is known as electrical conductivity.. Electrical conductivity is determined by the types of atoms of the material (the number of protons in the nucleus of an atom, which determines its chemical identity) and the way the atoms are connected to each otherohm. Materials with high electron mobility (many free electrons) are called conductors, and materials with low electron mobility (few or no free electrons) are called dielectrics.

Below are a few examples of the most common conductors and dielectrics:

Conductors:

• silver
• copper
• gold
• aluminum
• iron
• steel
• brass
• bronze
• Mercury
• graphite
• dirty water
• concrete

Dielectrics:

• glass
• rubber
• oil
• asphalt
• fiberglass
• porcelain
• ceramics
• quartz
• (dry) cotton
• (dry) paper
• (dry) wood
• plastic
• air
• diamond
• pure water

It should be understood that not all conductive materials have the same level of conductivity, and not all dielectrics equally resist the movement of electrons.. Electrical conductivity is similar to the transparency of some materials: materials that easily "transmit" light are called "transparent", and those that do not transmit it are called "opaque".". However, not all transparent materials transmit light equallyetc. Window glass- better than organic glass, and certainly better than "clear" fiberglass. It is the same with electrical conductors, some of them are better at passing electrons, and some are worse.

For example, silver is the best conductor in the list of "conductors" above, allowing electrons to pass through more easily than any other material on that list. Dirty water and concrete are also listed as conductive, but these materials are substantially less conductive than any metal.

Some materials change their electrical properties under different temperature conditions. For example, glass is a very good insulator at room temperature, but becomes a conductor when heated to a very high temperature. Gases such as air are normally insulators, but they also become conductors when heated to very high temperatures. high temperatures. Most metals, on the contrary, become less conductive when heated, and increase their conductivity when cooled. Many conductors become perfectly conductive ( superconductivity) at extreme low temperatures.

In the normal state, the movement of "free" electrons in a conductor is chaotic, without a definite direction and speed. However, through external influence it is possible to make these electrons move in a coordinated manner through the conductive material. We call this directed movement of electrons electricity, or electric shock. To be more precise, it can be called dynamic electricity as opposed to static electricity, in which the accumulated electric charge is stationary. Electrons can move through the empty space within and between the atoms of a conductor just like water flows through the void of a pipe. The above analogy with water is appropriate in our case, because the movement of electrons through a conductor is often referred to as a "flow".

Since the electrons move uniformly through the conductor, each of them pushes the electrons in front. As a result, all electrons move simultaneously. The start and stop of the electron flow throughout the conductor is virtually instantaneous, even though the movement of each electron may be very slow. We can see an approximate analogy in the example of a tube filled with marble balls:

The tube is filled with marbles in the same way that a conductor is filled with free electrons, ready to move under the influence of external factors. If you insert another marble into this filled tube on the left, then the last marble will immediately come out of it on the right.. Despite the fact that each ball traveled a short distance, the transmission of motion through the tube as a whole occurred instantly from the left end to the right, regardless of the length of the tubes.ki. In the case of electricity, the transfer of the movement of electrons from one end of a conductor to the other occurs at the speed of light: about 220,000 km. per second!!! Each individual electron travels through the conductor at a much slower pace.

If we want the electrons to flow in a certain direction to a certain place, we must lay a suitable path of wires for them, just as a plumber must lay a pipeline to bring water to the right place. To facilitate this task, wires are made of highly conductive metals such as copper or aluminium.

Electrons can only flow when they have the ability to move through the space between the atoms of the material.. This means that the electric current can be only where there is a continuous path of conductive material that allows the movement of electrons. By analogy with marbles, we can see that the marbles will "flow" through the tube only if it is open on the right side. If the tube is blocked, then the marble will "accumulate" in it, andthere will be no "flow" responsibly. The same is true for electric current: a continuous flow of electrons requires a continuous path for bothsintering of this flow. Let's look at the diagram to understand how it works:

The thin, solid line (shown above) is a schematic representation of a continuous piece of wire. Since a wire is made of a conductive material such as copper, its constituent atoms have many free electrons that are free to move around it. However, within such a wire there will never be a directed and continuous flow of electrons unless it has a place where the electrons come from and a place where they go. Let's add a hypothetical "Source" and "Receiver" of electrons to our circuit:

Now, when the Source supplies new electrons to the wire, a stream of electrons will go through this wire (as shown by the arrows, from left to right). However, the flow will be interrupted if the conductive path formed by the wire is damaged:

Due to the fact that air is a dielectric, the resulting air gap will divide the wire into two parts.. The once-continuous path is disrupted and electrons cannot flow from the Source to the Receiver.. A similar situation will occur if the water pipe is cut into two parts, and the ends at the cut point are clogged: in this case, water cannot flow.m. When the wire was one piece, we had an electrical circuit, and this circuit was broken at the time of damage.

If we take another wire and connect two parts of the damaged wire with it, then again we will have a continuous path for the flow of electrons.v. The two dots in the diagram show the physical (metal-to-metal) contact between the wires:

Now we again have a circuit consisting of a Source, a new wire (connecting the damaged one) and an Electron Receiver. Considering the plumbing analogy, by installing a tee on one of the clogged tubes, we can direct the water through the new pipe segment to its destination.I am. Note that there is no electron flow on the right side of the damaged wire because it is no longer part of the path from Source to Electron Destination.

It should be noted that the wires, in contrast to water pipes, which are eventually corroded by rust, there is no "wear and tear" from exposure to the electron flow. When electrons move, a certain friction force arises in the conductor, which can generate heat. We will consider this topic in more detail later.

Short review:

• V conductors, electrons located in the outer orbits of atoms can easily leave these atoms, or, on the contrary, join them. Such electrons are called free electrons.
  
• V dielectrics outer electrons have much less freedom of movement than in conductors.
• All metals are electrically conductive.
• dynamic electricity, or electricity is the directional movement of electrons through a conductor.
• Static electricity- this is a fixed (if on a dielectric), accumulated charge, formed by an excess or lack of electrons in an object.
• To ensure the flow of electrons, you need a whole, intact conductor, which will provide the reception and issue of electrons.

A source: Lessons In Electric Circuits

conductors conductors

substances that conduct electric current well, that is, they have high electrical conductivity (> 10 4 -10 6 Ohm -1 cm -1), due to the presence in them of a large number of mobile charged particles. They are divided into electronic (metals), ionic (electrolytes) and mixed, where the movement of both electrons and ions takes place (for example, plasma).

Conductors, substances that conduct electricity well due to the presence in them of a large number of mobile charged particles. Good conductors usually include substances with a resistivity of 10 -6 ohms. cm.
Conductors of electric current (conductor materials) can be solids, liquids, and, under appropriate conditions, gases.
Metals are solid conductors (cm. METALS), metal alloys (cm. ALLOYS), some modifications of carbon, as well as solid electrolytes (cm. SOLID ELECTROLYTES).
Liquid conductors include liquid metals (cm. LIQUID METALS) and various electrolytes (cm. ELECTROLYTES).
The mechanism of current passage in metals in solid and liquid state due to the directed movement of free electrons, therefore they are called conductors with electronic electrical conductivity or conductors of the 1st kind. At low temperatures, many metals and alloys pass into the superconducting state (see Superconductors (cm. SUPERCONDUCTORS)). Conductivity in solid electrolytes is provided by charge transfer by one type of ion.
The mechanism for the passage of current in liquid electrolytes, or conductors of the 2nd kind, is associated with the transfer along with the electric charges of the ions. Conductors of the 2nd kind are solutions (mainly aqueous) of acids, alkalis and salts, as well as melts of ionic compounds. As a result of the passage of current through such conductors, the electrolyte composition gradually changes, and electrolysis products are released on the electrodes.
All gases and vapors at low intensities electric field are not conductors. However, if the field strength is higher than a certain critical, then the gas can become a conductor with electronic and ionic electrical conductivities. In ionized gases and vapors of substances, including metal vapors, the passage of an electric current will be due to the movement of both electrons and ions, and the conduction mechanism will be mixed. A strongly ionized gas in which the concentrations of positive and negative charges are equal is called plasma. (cm. PLASMA).

encyclopedic Dictionary. 2009 .

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