The cathode and the anode are two components of oneprocess: the flow of electric current. All materials can be divided into two types - they are conductors, in the structure of which there is a large excess of free electrons, and dielectrics (there are practically no free electrons in them).
Conductors and dielectrics can be solid,liquid and gaseous substances. This is not essential for the flow of electric current. When the electromagnetic voltage is applied for a long time to the material, an excess of electrons will form on the cathode, and at the anode its shortage. If the voltage is applied for a sufficiently long time, then the bound electrons together with the atoms will break out of the structure of the material from which the anode is made, and the material itself will begin to react chemically with the reactive substances from the environment. This process is called electrolysis.
The cathode and anode in electrochemistry are twopoles of a constant electromagnetic voltage applied to saline solutions or melts. When the current flows from an excess of electrons, the anode begins to break down, i.e. the positively charged atoms of matter themselves will fall into the brine (the environment) and be transferred to the cathode, where it will settle in a purified form. This process is called galvanic. With the help of electroplating cover a thin layer of zinc, copper, gold, silver and other metals various products.
What is the cathode and what are the tasks that itperforms in electrolysis? This can be understood by doing the following: if an anode made of bronze or tin is made, then a printed circuit board, covered with a thin layer of copper or tin (used in the electronics industry), will be produced on the cathode. The same way get gilded jewelry, coppered and even gilded aluminum tips for electrical engineering in order to increase electrical conductivity.
Answers to questions about what an anode and a cathode are,when electrolysis is obvious: the anode as a result of the flow of direct current through the brine is destroyed, and the cathode takes over the anode material. Even such a term arose in the environment of electroplating - "anodizing the cathode". It does not carry physical meaning, but it displays the actual essence of the matter beautifully.
Semiconductors are materials,which in the structure do not have free electrons, and the atomic ones stay in their places badly. If such a material is placed in a liquid or gaseous state in a magnetic field and then allowed to solidify, an electrically structured semiconductor will be obtained, which will flow the current only in one direction.
a) with "p-n-p" conductivity;
b) with "n-p-n" conductivity.
In practice, this fineness of the structure of diodesdoes not matter. It is important to connect the diode correctly. Where is the anode, where the cathode is a question that many are puzzled about. On the diode there are special symbols: either A and K, or + and -. It is possible to connect the diode only in two ways to the DC electrical circuit. In one case, a functioning diode will conduct a current, and in the other, it will not. Therefore, it is necessary to take the device, on which it is known, where the cathode is, and where the anode, and connect it to the diode. If the device shows the presence of current, the diode is connected correctly. Hence, the cathode of the device and the cathode of the diode, as well as the anode of the device and the anode of the diode, coincided. Otherwise, you need to change the connections in places.
1. If the diode does not pass current in both directions, then it is burnt out, it can not be repaired.
2. If on the contrary, misses, then it is punched. It must be discarded.
Diodes are checked by testers and probes. In diodes, the cathode and anode are rigidly tied to their material design, unlike galvanic power sources (batteries, batteries, etc.).
If a diode is connected with one leg (electrode) toalternating voltage, then at the second electrode we get a positive or negative half-sine wave. If we connect the two diodes to the bridge, then we will observe a rectified electric practically constant current.
The cathode and anode in these products change places independing on the direction of the current flow, because in one case the voltage does not come to them, and they themselves serve as sources of direct current due to the chemical reaction. Then the negative electrode will already be the anode, and the positive electrode is the cathode. In the other case, the usual electrolysis process takes place in the battery.
When the battery is discharged and the chemicalThe reaction, which served as a source of electric current, ceased, it must be charged with an external power source. Thus, we start the process of electrolysis, i.e. restore the original properties of the galvanic battery. At the cathode of the battery, it is necessary to apply a negative charge already, and on the anode - positive, then the battery will be charged.
Thus, the answer to the question of how to determine the cathode and anode in a galvanic cell depends on whether it is charged or serves as a source of electric current.
As a summation of the foregoing, the cathode-it is an electrode on which an excess of electrons appears, and the anode is an electrode on which there is a shortage of electrons. But plus or minus a specific electrode element of the electrical circuit is determined by the direction of the flow of electric current.
