One of the most important definitions of physics is that an electric current is any ordered movement of particles having any charge. From this we can conclude that in order for an electric current to appear, it is necessary to have free electrons or ions in the metal, liquid, or some other material, which will move under the influence of an electromagnetic field. At the same time, the electric current in various environments will have certain features, because of which its flow in each of them will be different.
If we consider the features of the formation and flow of electric current in metals, then first of all it is worth paying attention to the very structure of metals, which is a crystal lattice. In this case, ions with a positive charge are located in the nodes of this lattice, and electrons with a negative charge move in a chaotic order in the space between these nodes. If an electric field is created around the metal, the motion of the electrons will take on a more ordered character. It can be concluded that in relation to metals, electric current is the directed movement of electrons.
The main characteristic of the flow of electric current in metals is the current-voltage expression, known as Ohm's law. According to this law, the current strength is in direct proportion to voltage and inversely to resistance. When analyzing electric current in various media, special attention should be paid to its formation and flow in a liquid medium.
Electric current in electrolytes occurs as a result of a reaction called electrolytic dissociation. Its essence is the decomposition of alkali molecules, salts or acids into positive and negative charged ions, which become carriers of an electric charge in liquids. The thing is that when an electromagnetic field begins to act on a solution, the chaotic movement of ions turns into an ordered one. In this case, positive ions begin to move toward the electrode having a negative charge, and negative ions toward a having a positive charge. Thus, unlike the same metals, the electric current in electrolytes is an ordered movement of ions. In addition, it is worth noting that during the passage of these ions through the solution, the formation of substances always occurs on the electrodes, which are the structural components of this solution, be it alkali, acid or salt. This phenomenon, called electrolysis, is actively used in industrial enterprises to produce pure metals, as well as for coating and polishing certain products.
Considering the electric current in various media, in particular, in metals and in liquids, we pointed out that in these substances free ions or electrons already exist. And what happens to a gas, which, as you know, consists of neutral molecules? An electric current without free particles with a negative or positive charge is impossible, therefore, to begin with, the gas must be ionized, that is, to create charged particles in it. The energy spent for this will be the ionization energy, which reaches maximum values for inert gases, and minimum - for alkali metal atoms . Ionization of the gas leads to the fact that three different types of charged particles are formed in it - electrons having a negative charge, as well as positive and negative ions. All these particles under the influence of an external field begin to move orderly, observing the same principle as when moving ions in liquids. Thus, the electric current in gases is a directed movement of both ions (positive and negative) and electrons.
Concluding, the following can be noted: electric current in various environments has its own characteristics, which are widely used in various fields of the national economy, as well as in scientific research experiments.