The classification of materials with respect to the ability to conduct electric current. The most 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:

first kind with electron-based conductivity;
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 values \u200b\u200band is directly proportional to the voltage value.

The best electrical conductors under ordinary conditions are silver, gold, copper and aluminum. Copper and aluminum are most widely used for the manufacture of various wires and cables due to the lower price. A good liquid conductor of the first kind is mercury. It conducts electric current and carbon well. But due to the lack of flexibility, its use is impossible. However, the relatively recently created form of carbon graphene allows the manufacture of threads and cords from threads.

But graphene cords have a resistance that is unacceptably large for conductors. Therefore, they are used in electric heaters. In this quality, the graphene cord is superior to metal wire analogues based on an alloy of nickel and chromium, since it can provide a higher temperature. Similarly, tungsten wire conductors are used. Incandescent spirals and electrodes of discharge lamps are made of them. Tungsten is the most refractory electrical conductor.

Conductor Processes

The electric current flowing in the conductor has certain effects on it. In any case, an increase in temperature occurs. But chemical reactions are also possible, which lead to a change in physical and chemical properties. The greatest changes are subject to electrical conductors of the second kind. The electric current in them causes an electrochemical reaction called electrolysis.

As a result, the ions of a 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 the acid, alkali, or salt. Electrolysis is widely used to produce many pure chemicals from natural raw materials. By the method of electrolysis of melts, pure aluminum and some other metals are obtained.

Conductors of the first and second kind can not only conduct electric current when external voltage is applied to them. In the interaction of, for example, lead with an acid, that is, a first-type conductor with a second-type conductor, an electrochemical reaction occurs that provides the release of electrical energy. The battery device is based on this.

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

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

The economically viable 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 electric current. But this is a completely different story ...

Electric conductor

Electric wire

Conductor - a substance that conducts electric current. Among the most common solid conductors are known metals, semimetals. An example of conductive fluids is electrolytes. An example of conductive gases is ionized gas (plasma). Under normal conditions, some substances that act as insulators can go into a conducting state, 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 busbars.

The microscopic description of conductors is associated with the electronic theory of metals. The simplest model for describing 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)

Literature

Jean M. Rabai, Ananta Chandrakasan, Borivezh Nikolic 4. Explorer // Digital integrated circuits. Design Methodology \u003d Digital Integrated Circuits. - 2nd ed. - M.: "Williams", 2007. - S. 912. - ISBN 0-13-090996-3

Wikimedia Foundation. 2010.

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

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

1. conductors - which pass electric current;

2. dielectrics - possess 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 connected, electric charges that can begin to move under the influence of an 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, bodies of people and animals are also good conductors of electric charges.

If we 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 that are not held by the bonds of atoms. They characterize the magnitude of the 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 corresponding unit: siemens (cm).

1 cm \u003d 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 units of measurement of these electrical quantities - a current-voltage characteristic.

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

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

When an electric current passes through metal conductors, neither their mass nor their chemical composition changes. Consequently, metal atoms do not participate in the transfer of electric charges. Studies of the nature of 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:

bonded by atomic adhesion forces;

free.

Electrons held in orbit by the attractive forces of an atomic nucleus, as a rule, do not participate in the creation of an electric current under the action of external electromotive forces. Otherwise, free particles behave.

If EMF is not applied to the 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 time.

When an external field energy with intensity E is applied to a 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 the Ohm's law for the site and the complete circuit.

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

alloys;

individual carbon modifications (graphite, coal).

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

If metals and alloys are placed in an environment of ultra-low temperatures, then they become superconducting.

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, salts of acids;

melts of various ionic compounds;

various gases and vapors.

Electric current in a liquid

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

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

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

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

In addition to liquids, solid electrolytes also exist in nature. They are called superionic conductors (superionics), which have a crystalline structure and the ionic nature of chemical bonds, which causes high electrical conductivity due to the movement of ions of the same type.

Hole Conductors

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 a 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 the separation of bound electrons. It is called ionization energy.

The semiconductor has an electron-hole transition. 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 Flux

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

In other types of materials, such as glass, electrons in atoms have very little freedom of movementi am. However, external forces, such as physical friction, can 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 electron mobility in a material is known as electrical conductivity.. The 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 atoms are joined togetherohm 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.

The following 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
china
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 conductivity level, and not all dielectrics equally resist the movement of electrons. Electrical conductivity is similar to the transparency of some materials: materials that easily "pass" light are called "transparent", and those that do not pass it are called "opaque". However, not all transparent materials pass equallyem. Window glass is better than organic glass, and certainly better than "clear" fiberglass. The same is true for electrical conductors, some of which pass electrons better, and some worse.

For example, silver is the best conductor in the above list of "conductors", providing an easier passage of electrons than any other material from this list. Dirty water and concrete also appear as conductors, 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 dielectric at room temperature, but becomes a conductor if it is heated to a very high temperature. Gases, such as air, are dielectrics in the normal state, but they also become conductors when heated to very high temperatures. Most metals, by contrast, become less conductive when heated, and increase their conductivity when cooled. Many conductors become perfectly conductive ( superconductivity) at extremely low temperatures.

In the usual state, the motion of “free” electrons in a conductor is chaotic, without a specific direction and speed. However, by external action, these electrons can be made to move coordinated through a conductive material. Such directional motion of electrons we call electricity, or electric shock. To be more precise, it can be called dynamic electricity unlike static electricity, in which the accumulated electric charge is stationary. Electrons can move in the empty space inside and between the atoms of the 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 beginning of the motion and the stop of the electron flux along the entire length of the conductor are practically instantaneous, even though the movement of each electron can be very slow. We can see an approximate analogy on the example of a tube filled with marble balls:

The tube is filled with marble balls just like a conductor is filled with free electrons, ready to move under the influence of external factors. If you insert another marble ball into this filled tube on the left, then the last ball immediately leaves it on the right. Despite the fact that each ball passed 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 tubeski. In the case of electricity, the transfer of the movement of electrons from one end of the conductor to the other occurs at the speed of light: about 220,000 km. per second!!! Each individual electron passes through the conductor at a much slower pace.

If we want electrons to flow in a certain direction to a certain place, we must make the appropriate path for them from the wires, just like a plumber must lay a pipeline to bring water to the right place. To facilitate this task, wires made from well-conductive metals such as copper or aluminum.

Electrons can only flow when they have the ability to move in the space between the atoms of the material. This means that electric current can be only where there is a continuous path of conductive material that allows the movement of electrons. By analogy with marble balls, we can see that the balls 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, and withthere will be no responsible flow. The same is true for electric current: a continuous stream of electrons requires a continuous path for bothsintering this flow. Let's look at the diagram to understand how this works:

The thin, solid line (shown above) is a schematic designation of the continuous portion of the wire. Since the wire is made of a conductive material such as copper, the atoms that make it up have many free electrons that can move freely 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 places where they go. Let's add hypothetical "Source" and "Recipient" of electrons to our scheme:

Now, when the Source delivers new electrons to the wire, an electron stream will go through this wire (as shown by 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 broken, and electrons cannot flow from the Source to the Recipient. A similar situation will turn out if you cut the water pipe into two parts, and plug the ends in the place of the cut: water in this case cannot flowt. When the wire was one, we had an electric circuit, and this circuit was broken at the time of the 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 electron flowat. Two points in the diagram show the physical (metal-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 Recipient. If we consider the analogy with water supply, then installing a tee on one of the clogged tubes, we can direct water through a new segment of the pipe to the destinationi 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 the Source to the electron receiver.

It should be noted that the wires, unlike water pipes, which ultimately corrode by rust, no "wear" from the effects of the electron flow threatens. When electrons move, a certain friction force arises in the conductor, which can generate heat. We will discuss this topic in more detail later.

Short review:

AT conductors, the electrons located on the outer orbits of atoms can easily leave these atoms, or vice versa join them. Such electrons are called free electrons.
AT dielectrics external 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, a whole, intact conductor is needed, which will ensure the reception and delivery of electrons.

Source: Lessons In Electric Circuits

Conductors conductors

substances that conduct electricity well, that is, have high electrical conductivity (\u003e 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 both electrons and ions (for example, plasma) move.

CONDUCTORS

CONDUCTORS, substances that conduct electrical current well due to the presence of a large number of mobile charged particles in them. Good conductors usually include substances with a resistivity of 10 -6 ohms. cm.
Conductors of electric current (conductive materials) can be solids, liquids, and, under appropriate conditions, gases.
Solid conductors are metals (cm. METALS)metal alloys (cm. ALLOYS)some carbon modifications as well as solid electrolytes (cm. SOLID ELECTROLYTES).
Liquid conductors include liquid metals. (cm. LIQUID METALS) and various electrolytes (cm. ELECTROLYTES).
The mechanism of the passage of current in metals in the solid and liquid state is due to the directed motion of free electrons, therefore they are called conductors with electronic electrical conductivity or conductors of the first kind. At low temperatures, many metals and alloys go into the superconducting state (see Superconductors (cm. SUPERCONDUCTORS)) Conductivity in solid electrolytes is ensured by charge transfer by one type of ion.
The mechanism of the passage of current in liquid electrolytes, or conductors of the 2nd kind, is associated with the transfer of ions together with the electric charges. 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 electric field intensities are not conductors. However, if the field strength is above a certain critical value, then the gas can become a conductor with electronic and ionic conductivities. In ionized gases and vapors of substances, including metal vapors, the passage of electric current will be due to the movement of both electrons and ions, and the conduction mechanism will be mixed. A highly ionized gas in which the concentrations of positive and negative charges are equal is called a plasma (cm. PLASMA).

encyclopedic Dictionary. 2009 .

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