How to define the cathode and anode + description
Among the terminology in the field of electrical engineering there are such concepts as cathode and anode. This can apply to power supplies, chemistry, physics and electroplating. The term can also be found in vacuum and semiconductor electronics. They can designate the conclusions or even the contacts of the device, and also what electrical sign they will have.
In this article you will learn about what it is, and also how to determine the cathode and anode in a diode, an electrolyzer, a battery, where they have a plus and where a minus.
In the field of electrochemistry, there are a couple of main sections:
- Electroplating elements - the production of electrical energy due to chemical reactions. Such elements include rechargeable batteries and batteries. They are also often referred to as a chemical current source.
- Electrolysis is the impact on a chemical type of reaction with electrical energy, in other words, a certain reaction is triggered by a power source.
We propose to consider redox reactions in cells of galvanic type, and then such processes occur on its electrodes?
But the electrode on which the oxidative reaction will occur is called reduction.
Hence the question arises - where is the minus, and where is the plus for the battery? Based on the definition, for galvanic cells, the anode will give up the electrodes.
Please note that GOST 15596-82 gives the official formulation of the names of the output of chemical current sources, in short, the plus will be only at the cathode, and the minus at the anode.
In this case, the flow of electricity through the conductor of the external circuits from the oxidizer (i.e., the cathode) to the anode, namely to the reducing agent, will be considered. Since electrons in the circuit will flow from minus to plus, and electricity is vice versa, and in this case the cathode will be a plus, and the anode will be a minus. By the way, the current will always flow into the anode.
Such processes are similar and reverse to galvanic cells, since it is not energy that comes from a chemical reaction, but on the contrary - the chemical reaction will occur due to an external source of electricity. In this case, the plus of the power supply will still be called the cathode, and the minus the anode. But the contacts of a charged galvanic cell or electrolyzer electrodes are already capable of bearing opposite names, and it is necessary to figure out why.
Important! When the galvanic cell of the cell is discharged, the anode is a minus, and the cathode is a plus; when charging, everything will be the other way around.
Since the current from the positive terminal of the power supply will flow to the positive terminal of the battery, the latter, by the way, will no longer be able to be a cathode.
Referring to the above, we can conclude that in this case, the battery electrodes are symbolically swapped during charging. In this case, through the electrode of the charged galvanic cell, into which the current of electricity flows, is called the anode. So, when charging, the plus of the battery will become the anode, and the minus will be the cathode.
Metallic deposition processes as a result of a chemical-type reaction under the action of electric current (during the electrolysis process) is called electroplating. It turns out that the world began to receive gilded, silver-plated, chrome-plated or even plated with other metals ornaments, as well as details.
Such a process is used as decorative, and also for applied purposes - in order to improve the corrosion resistance of various units and mechanisms of units. The method of operation of installations for applying a coating of galvanic type will lie in the use of solutions of salts of elements, which will cover the part, in the role of an electrolyte.
Determining where the anode is and where the cathode is in electroplating is also important. It is in this case that the anode will be the electrode to which the positive terminal of the power supply is connected, but it turns out that the cathode in this case will become a minus. In this case, the metal will be deposited (reduced) on the negative electrode (we are talking about the reduction reaction).
It turns out that if you want to make a gold-plated ring yourself - connect the negative terminal of the power supply to it and place it in a container with the required solvent.
The legs or electrodes of semiconductor and vacuum electronic devices are often called the cathode and anode. We propose to consider the conventional designation of the graphic type of a semiconductor diode according to the scheme. As you can see, the anode of the diode is connected to the battery plus. It is so called for the reason that current will flow into such an output from the diode.
On a real cell on the cathode there will be a dot or strip marking in the water. With the LED, everything is the same, and at 0.5 cm LEDs, the insides are visible through the bulb. The larger half is the cathode. The situation will be similar even with a thyristor, the purpose of the output and the unipolar use of such three-legged components makes it a controlled diode.
In a vacuum-type diode, the anode is also usually connected to plus, and the cathode to minus, as shown in the diagram. Although, when a voltage of the opposite type is applied, the names of the elements will not change, despite the flow of electric current in the opposite direction, even if it is insignificant. With passive elements, namely capacitors and resistors, things will be different.The resistor will not separate the anodes and cathodes separately, the current in it can begin to flow in any direction. You can give any name for its conclusions, and it all depends on the situation, as well as the considered scheme.
For simple non-polar capacitors, everything is exactly the same. Less often, such a division by contact names will be observed in electrolytic capacitors.
So, it is important to summarize, answering the question - how to remember, where is the plus, and where is the minus at the anode and cathode? There is a convenient mnemonic rule for electrolysis, battery charging, electroplating, and semiconductor devices. Such words with similar names have the same number of letters, as shown below. In all the cases listed above, the current will flow out of the cathode and will flow into the anode.
Do not be confused by the constant confusion "Why, when the battery when charging, the cathode becomes negative, but under normal circumstances it is positive?" It should be remembered that for all elements of electronics, as well as for electroplating and electrozers - in general, for your energy consumers, an anode can be called an output that is connected to a plus. The differences will end there, and now it will be easier for you to understand what is a minus, what is a plus between the pins of devices and elements. Finally, you should watch a useful video on the topic of the article. Now you know exactly what a cathode and anode are, and remember them very quickly. We hope this information was interesting for you, and also useful.
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