When using electrical appliances, a person is constantly faced with substances that are conductors, semiconductors and non-conducting dielectrics. These materials differ in the degree of electrical conductivity. In order to work with household appliances, you need to know all their features and characteristics. You can choose the best conductor of electric current from metals.
Content
- Features of the concept
- First and second kind
- Processes in electrical conductors
Features of the concept
Current conductors are those substances in which the number of free electric charges exceeds the number of bound ones. They can begin to move under the influence of an external force. The state of materials can be gaseous, solid and liquid. Electricity can flow through a metal wire if it is connected between two conductors of different potentials.
The current is carried by electrons that are not connected to each other by atoms. It is they who are able to characterize the ability of an object to pass electric charges through itself, or the amount of current conductivity. Its value is inversely proportional to the resistance, it is measured in siemens: Cm = 1 / Ohm.
The main carriers of electricity in nature are ions, holes and electrons. Therefore, the ability to conductance is divided into three types:
- ionic;
- electronic;
- hole.
The applied voltage makes it possible to evaluate the quality of the conductor. This ability of a substance is also called the volt-ampere characteristic.
First and second kind
After it turned out to figure out what conducts an electric current, you need to find out the features of some substances. Conductors can be different - metal wire, sea water. But in them the current is different, therefore, substances are divided into two groups:
- the first kind, in which electricity flows through electrons;
- the second type is based on ions.
The first includes all metals and carbon. The second kind includes alkalis, acids, salt melts - electrolytes. In them, the current represents the ordered movement of negative and positive ions. Electricity in such materials flows at any voltage. Under normal conditions good conductor of electric current Is a product made of gold, silver, aluminum or copper.
The latter two materials are used to produce cables that are notable for their low cost. A high-quality liquid substance that conducts current is mercury, and the current flows well through carbon. But this substance is not flexible, so it is not used in practice. Although physicists have recently been able to imagine carbon in the form of graphene, which has made it possible to make cords from its filaments.
In graphene products, the resistance is such that it is unacceptable for conductors. They can only be used in heaters. In this case, nickel and chromium metal wires lose, since they cannot withstand very high temperatures. The spirals in fluorescent lamps are made from tungsten. This material is capable of incandescence, since the substance is refractory.
Processes in electrical conductors
During the flow of electricity, the conductor gets under a certain influence. The most important thing is the rise in temperature. They also release some chemical reactions that can change the physical properties of a substance. Most of all, conductors of the second kind are exposed to this influence. They undergo a chemical reaction called electrolysis.
Ions of substances about electrical poles get the necessary charge and restore the original state that they had before the formation of alkali, acid or salt. Through electrolysis, chemists and physicists can obtain pure chemicals from natural raw materials. In this way, aluminum and other types of metals are created.
Substances of the first and second kind are involved in processes other than the conduction of electricity. For example, when an acid interacts with lead, a chemical reaction occurs that causes a current to be released. All batteries work according to this principle. The conductors of the first group can change when in contact with each other. During operation, copper and aluminum must be covered with a special sheath, otherwise both metals will simply melt. Humid air will cause an electrochemical reaction to occur. Therefore, the conductors are covered with a layer of varnish or other protective material.
Some conductors cannot resist electricity in cold air. This phenomenon is called superconductivity, which corresponds to a temperature value close to the chemical state of liquid helium. But research has led to the fact that there are new conductors with high temperatures.
Such substances were discovered in the 20th century. Ceramics of oxygen, barium, copper and lanthanum do not conduct current under normal conditions, but after heating it becomes superconductor. In practice, it is beneficial to use substances that can pass electricity at 58 degrees Kelvin and above - a temperature above the boiling point of nitrogen.
Liquids and gases conducting current are used less often than solids. But they are also necessary for the manufacture of modern electrical devices.
