Electrotechnics: Basics


Electric current in liquids and melts

Free charge carriers - ions

Free electric charges are not only in metals and it is not only the electrons. There is also free charge carriers, which are called - ions. What they are and what is the difference from elementary particles such as the electron, proton, neutron, photon? Good question.

They have in common that they both (except for the neutron and photon) have a certain amount of electric charge. For electrons and protons - it's always the elementary charge, and for the magnitude of the charge of the ions can be more than one elementary, but it is always a multiple of it. Next their community - this is their freely. Both are related, and thus are free to change the characteristics of its motion under the influence of an electric field.

Negative ion - anion and positive ion - cation

Differences between ions and elementary charges (protons and electrons) that ions - atoms of the chemical substances of the periodic table and isotopes. These atoms have feature. In its composition they have more electrons than normal, or they have lost their electrons. This may be many electrons per atom, or just a single. Besides electron atom there is also protons, but the loss of or accession means of nuclear reactions and changes in the structure of the atom. Ions can also be varied compounds atoms - that is, molecules and radicals. But consider for simplicity the examples on the basis of atoms.

Ions are two signs - positive +Q and negative -Q. To receive the atom (+) charge, it is enough to lose at least one electron in its orbit, then the balance will be disrupted and protons becomes larger than that of electrons. There is a deficit, the lack of electrons, atoms begin to crave to get a new electron. Such an atom turns into a positive ion, or else call it more cation. To obtain a negative ion (-), which is also called an anion sufficiently electrically neutral atom attached at least one extra electron.

Electric current of free charges - ions

Conduction current that exists in metals, where the free charge carriers are electrons, and the current in the liquids and melts, characterized in effects produced. Of course, have a lot in common, first of all - is the flow of electricity dq/dt is not equal to zero, i.e. in the cross section perpendicular to the direction of electric current changes the amount of charge. Also, the electric current is accompanied by the release of energy in the form of heat radiation and magnetic phenomena. Of the differences can be distinguished primarily electrochemical conversion substance, and in most cases no ability shielded from external electromagnetic fields.

Electric current in electrolytes and melts

In addition to these differences, there is one important point. For the existence of an electric current source is needed. It is difficult to find a source of current, which is exuded to ions, virtually all known sources of electricity - are sources of free electrons. This is due to the fact that the ions - is unstable state atoms and molecules, in contrast to the stable and ubiquitous electrons.

When through a conductor, which consists of free ions flowing electricity, where the source at one end has an excess of electrons, and on the other the lack of them, will inevitably free ions on one pole receive missing their electrons and become neutral, and at the other end with an excess of electrons ions -They give too much, and also become neutral. To put the language of chemistry, there is a reaction of the electrochemical reduction and oxidation. Where ions give the missing electrons to the cathode ("minus"), and going to the ions are called cations. Where rob ions, called anions, the extra electron, there will be the anode ("plus").

The cations move toward the cathode. Anions move toward the anode. In designating polarity power sources currently represent exactly the cathode and anode. The cathode - a "minus" sign at the source, and the anode - "plus" sign to the source. In conductor, where the free carriers - electrons having the sign of the charge (-), there is a current flow from the cathode to the anode, that is, from "minus" to "plus".

This may seem strange, because in the literature usually denoted by the arrow direction of the current, and it is shown as coming from the "plus" to "minus". Do not let that fool you. The fact that the original "plus" refers to the excess electricity, and "minus" disadvantage. Electricity flows from the place where his lot, where it does not exist, but where it is looking forward to. In addition, electricity is divided into two kinds, positive and negative, and then was discovered the elementary charge - the electron, which was given the sign "minus"(-). As a result, there was one kind of electricity - negative, but the polarity of habit designated for positive electricity. That is why and show the current direction of the "plus" to "minus", although in fact there is a movement of charges in the reverse order.

If there is a conductor where only anions, they will move toward the anode, if the conductor is only cations, they will move toward the cathode. Always on the contrary, it is a plus to minus and minus to plus. It may well be that the conductor has both types of ions, then each of them will move to their side. As a result, to get traffic in both directions. Question. What about the value of the current? It seems like it turns out that one has gone through the section number of charges (anions), and went a different number (cations). In this case, the charges are added to the account of their polarity signs.

Another difference from the conduction current is the temperature dependence. For metals, the increase in temperature degrades their conductivity, resistance of metals by heating increases. In the case of conductive liquids inverse dependence. The increase in temperature improves motility ions upon heating of the conductive fluid resistance decreases.

Electrolytes and melts

Many chemical compounds capable of dissolving in water. This dissolution is called electrolytic dissociation. However, dissociation is possible without the participation of water. Enough to melt the crystals of the chemical compound and a melt. Water has a phenomenal ability to dissolve in itself almost all chemical elements. Oceans is a solution of ions of almost all elements of the periodic table.

Each of you had to eat electrolytes, if only because we are writing we salt and salt solution in water and has an electrolyte. However, it should be noted that the dissolution of the sugar in the water - is not an electrolyte, because there is no disintegration of the sugar molecules into ions.

Gastric juice, blood, lymph, all fluids in the human body are electrolytes. We are with you, animals and plants - all are made up of electrolytes. And what exactly is the electrolyte? The electrolyte solution is called (usually water) or melt ions. All electrolytes are called conductors of the second kind. There are weak and strong electrolytes in the degree of dissociation. Most inorganic acids refers to the strong electrolytes, but the water is a weak electrolyte. However, water is still considered to be the conductor of the second kind. Distilled water is a poor conductor of electricity, but it is only in a salt solution, or add to it an acid or alkali, so it improves the conductivity significantly.

The electrolytes used in chemical power sources, such as galvanic cells and batteries. In production processes electroplating and electrochemistry, electrolytes are also used and are using electrochemical processes running during the flow of electricity through the fluid.

Melts substances just as aqueous electrolytes are conductors of the second kind, and may be called electrolytes. To obtain aluminum from alumina, using their melts. Electricity was passed through alumina and the process of electrolysis, and one of the electrodes, pure aluminum. This is a very energy-intensive process, but it is similar to how the decomposition of water into hydrogen and oxygen by an electric current.

Liquid dielectrics

Not all of the liquid electrolytes are not all fusions will contain the free ions. If no ion-free solution is only a small number of free electrons, this solution will conduct electricity therethrough permit passage of electric current, but such a solution can not be called conductor of the second kind, and especially the conductor of the first kind. Such material will behave as a dielectric and insulating properties to be more than conductivity.

Date: 02.01.2016

© Valentin Grigoryev

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