In order to draw up a diagram of a galvanic cell, it is necessary to understand the principle of its actions, structural features.
Consumers rarely pay attention to rechargeable batteries and batteries, and it is these current sources that are the most popular.
Chemical current sources
What is a galvanic cell? Its scheme is based on an electrolyte. The device includes a small container where the electrolyte adsorbed by the separator material is located. In addition, the circuit of two galvanic cells suggests the presence of a cathode and anode. What is the name of such a galvanic cell? The scheme linking the two metals together suggests the presence of a redox reaction.
The simplest galvanic cell
It implies the presence of two plates or rods made of different metals, which are immersed in a solution of a strong electrolyte. In the process of operation of this galvanic cell, an oxidation process is carried out at the anode associated with the return of electrons.
At the cathode, reduction is accompanied by the adoption of negative particles. Electrons are transferred along the external circuit to the oxidizing agent from the reducing agent.
Example of a cell
In order to compile electronic circuits of galvanic cells, it is necessary to know the value of their standard electrode potential. Let us analyze a variant of a copper-zinc galvanic cell operating on the basis of the energy released during the interaction of copper sulfate with zinc.
This galvanic cell, the circuit of which will be given below, is called the Jacobi-Daniel cell. It includes a copper plate, which is immersed in a solution of copper sulfate (copper electrode), and it also consists of a zinc plate in a solution of its sulfate (zinc electrode). The solutions are in contact with each other, but in order to prevent their mixing, the element uses a partition made of porous material.
Operating principle
How does a galvanic cell function, the circuit of which is of the form Zn ½ ZnSO4 ½½ CuSO4 ½ Cu? During its operation, when the electric circuit is closed, the process of oxidation of metallic zinc occurs.
On its surface of contact with a salt solution, the transformation of atoms into Zn2 + cations is observed. The process is accompanied by the release of "free" electrons that move along the external circuit.
The reaction proceeding on a zinc electrode can be represented as follows:
Zn = Zn2 + + 2e-
The recovery of metal cations is carried out on a copper electrode. Negative particles that get here from the zinc electrode combine with copper cations, precipitating them in the form of a metal. This process has the following form:
Cu2 + + 2e- = Cu
If you add up the two reactions discussed above, you get the total equation that describes the operation of the zinc-copper galvanic cell.
A zinc electrode acts as an anode; copper serves as a cathode. Modern galvanic cells and batteries require the use of a single electrolyte solution, which expands the scope of their application, makes their operation more comfortable and convenient.
Varieties of galvanic cells
The most common are carbon-zinc elements. They use a passive carbon current collector in contact with the anode, which is manganese oxide (4). The electrolyte is ammonium chloride, used in a paste form.
It does not spread, so the galvanic cell itself is called dry. Its feature is the ability to "recover" throughout the work, which positively affects the duration of their operational period. Such galvanic cells have a low cost, but low power. With a decrease in temperature, they decrease their efficiency, and with its increase, the electrolyte gradually dries up.
Alkaline elements involve the use of an alkali solution, and therefore have quite a few applications.
In lithium cells, an active metal acts as an anode, which positively affects the service life. Lithium has a negative electrode potential, therefore, with small dimensions, such elements have a maximum rated voltage. Among the shortcomings of such systems, one can single out a high price. Opening lithium current sources is explosive.
Conclusion
The principle of operation of any galvanic cell is based on redox processes taking place at the cathode and anode. Depending on the metal used, the selected electrolyte solution, the service life of the cell, as well as the value of the nominal voltage, changes. Currently, lithium, cadmium galvanic cells having a sufficiently long service life are in demand.