Designation of different types of diodes in the diagram. The diode in the diagram is where the anode is and where the cathode is. Anode and cathode - what is it and how to determine it correctly

Anode in electrochemistry

Anodes - plural of "anode"; this form is used primarily in metallurgy, where anodes are used for electroplating, used to apply a layer of metal to the surface of a product by an electrochemical method, or for electrorefining, where the metal with impurities is dissolved at the anode and deposited in a purified form on the cathode. The most widely used anodes are made of zinc (there are spherical, cast and rolled, the latter are more often used), nickel, copper (among which copper-phosphorus, AMF grades are separately distinguished), cadmium (the use of which is being reduced due to environmental hazards), bronze, tin (used in production printed circuit boards in the radio-electronic industry), an alloy of lead and antimony, silver, gold and platinum. Anodes made of base metals are used to increase corrosion resistance, improve the aesthetic properties of objects, and other purposes. Anodes made of precious metals are used in galvanic production to increase the electrical conductivity of products, etc.

Anode in vacuum electronic devices

Anode and cathode sign

Found in literature different designation the sign of the anode - “+” or “-”, which is determined, in particular, by the features of the processes under consideration.

In electrochemistry, it is generally accepted that the cathode is the electrode on which the reduction process occurs, and the anode is the one where oxidation occurs. When an electrolyzer is operating (for example, when refining copper), an external current source provides an excess of electrons (negative charge) on one of the electrodes; this is where the metal is reduced, this is the cathode. The other electrode ensures a lack of electrons and oxidation of the metal; this is the anode.

In electrical engineering, the anode is a positive electrode, current flows from the anode to the cathode, electrons, respectively, vice versa.

See also

• Mnemonic rules for remembering the anode sign

Literature

Links

• // Encyclopedic Dictionary of Brockhaus and Efron: In 86 volumes (82 volumes and 4 additional ones). - St. Petersburg. , 1890-1907.
• IUPAC recommendations for the choice of sign for the values ​​of anodic and cathodic currents

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See what “Anode” is in other dictionaries:

- (Greek anodos ascending road). In a galvanic cell, one of two plates or wires through which a liquid enters or exits electric current. The opposite of a cathode. Dictionary of foreign words included in the Russian language... Dictionary of foreign words of the Russian language

anode- a, m. anode f., English. anode gr. anodos way up, ascension. physical Positively charged electrode. In the operation of devices such as a galvanic battery, there is no polarity and cannot be.. positive and negative poles..… … Historical Dictionary of Gallicisms of the Russian Language

Negative electrode Dictionary of Russian synonyms. anode noun, number of synonyms: 1 electrode (10) ASIS Dictionary of Synonyms. V.N. Trishin... Dictionary of synonyms

anode- electric vacuum device; anode; industry collector An electrode whose main purpose is usually to receive the main flow of electrons during an electrical discharge... Polytechnic terminological explanatory dictionary

anode- (devices) an electrode through which electric current enters a medium having a specific conductivity different from the specific conductivity of the anode [ST IEC50 (151) 78] anode EN anode electrode capable of emitting positive charge... ... Technical Translator's Guide

- (from the Greek anodos upward movement, ascent), the electrode of an electronic or electrical device (for example, vacuum tube, galvanic cell, electrolytic bath), characterized by the fact that the movement of electrons in the external... ... Modern encyclopedia Ozhegov's Explanatory Dictionary

- (from the Greek anodos upward movement), 1) the electrode of an electronic or ionic device, connected to the positive. source pole. 2) Pos. electrical source electrode current (galvanic cell, battery). 3) Positive electric electrode arcs...... Physical encyclopedia

Among the terms in electrical engineering there are such concepts as anode and cathode. This applies to power supplies, electroplating, chemistry and physics. The term is also found in vacuum and semiconductor electronics. It denotes the terminals or contacts of devices and what electrical sign they have. In this article we will tell you what an anode and a cathode are, as well as how to determine where they are located in the electrolyzer, diode and battery, which is a plus and which is a minus.

Electrochemistry and electroplating

Electrochemistry has two main branches:

1. Galvanic cells - the production of electricity through a chemical reaction. These items include batteries and accumulators. They are often called chemical current sources.
2. Electrolysis is the effect of electrical energy on a chemical reaction, in simple words– using a power source, some kind of reaction is triggered.

Let's consider the redox reaction in a galvanic cell, then what processes take place at its electrodes?

• Anode– electrode on which it is observed oxidation reaction, that is, he donates electrons. The electrode at which the oxidation reaction occurs is called reducing agent.
• Cathode– the electrode on which the flow occurs reduction reaction, that is, he accepts electrons. The electrode at which the reduction reaction occurs is called oxidizing agent.

This raises the question - where is the plus and where is the minus of the battery? Based on the definition, a galvanic cell the anode gives up electrons.

Important! GOST 15596-82 gives the official definition of the names of the terminals of chemical current sources; in short, the plus is on the cathode and the minus is on the anode.

IN in this case the flow of electric current is considered via external circuit conductor from oxidizer (cathode) To restorer (anode). Since electrons in a circuit flow from minus to plus, and electric current vice versa, then the cathode is plus and the anode is minus.

Attention: current always flows into the anode!

Or the same in the diagram:

The process of electrolysis or battery charging

These processes are similar and inverse to a galvanic cell, since here it is not the energy that comes from a chemical reaction, but on the contrary - the chemical reaction occurs due to external source electricity.

In this case, the plus of the power source is still called the cathode, and the minus the anode. But the contacts of the charged galvanic cell or the electrodes of the electrolyzer will already have opposite names, let's figure out why!

Important! When a galvanic cell is discharged, the anode is minus, the cathode is plus, and when charging it is the other way around.

Since the current from the positive terminal of the power source flows to the positive terminal of the battery, the latter can no longer be the cathode. Referring to the above, we can conclude that in this case, the battery electrodes conditionally change places when charging.

Then, through the electrode of the charged galvanic cell, into which electric current flows, it is called the anode. It turns out that when charging the battery, the plus becomes the anode, and the minus becomes the cathode.

The processes of metal deposition as a result of a chemical reaction under the influence of electric current (electrolysis) are called electroplating. Thus, the world received silver-plated, gilded, chrome-plated or coated with other metals jewelry and parts. This process is used for both decorative and applied purposes - to improve the corrosion resistance of various components and assemblies of mechanisms.

Operating principle of application units electroplating lies in the use of solutions of salts of the elements with which the part will be coated as an electrolyte.

In electroplating, the anode is also the electrode to which the positive terminal of the power source is connected, respectively, the cathode in this case is the negative one. In this case, the metal is deposited (reduced) on the negative electrode (reduction reaction). That is, if you want to make a gold-plated ring with your own hands, connect the negative terminal of the power supply to it and place it in a container with the appropriate solution.

In electronics

The electrodes or legs of semiconductor and vacuum electronic devices are also often called anode and cathode. Consider the conditional graphic designation semiconductor diode on the diagram:

As we can see, the anode of the diode is connected to the positive of the battery. It is called that for the same reason - current flows into this terminal of the diode in any case. On a real element, there is a marking on the cathode in the form of a stripe or dot.

The LED is similar. On 5 mm LEDs the insides are visible through the bulb. The larger half is the cathode.

The situation is also the same with the thyristor, the assignment of the terminals and the “unipolar” use of these three-legged components make it a controlled diode:

For a vacuum diode, the anode is also connected to the positive, and the cathode to the negative, as shown in the diagram below. Although when applying reverse voltage– the names of these elements will not change, despite the flow of electric current in the opposite direction, albeit insignificant.

The situation is different with passive elements such as capacitors and resistors. A resistor does not have a separate cathode and anode; current in it can flow in any direction. You can give any name to its conclusions, depending on the situation and the circuit in question. For ordinary non-polar capacitors Also. Less commonly, such a separation by contact names is observed in electrolytic capacitors.

Conclusion

So, let’s summarize by answering the question: how to remember where the plus and minus are at the cathode and anode? There is a convenient mnemonic rule for electrolysis, battery charging, electroplating and semiconductor devices. These words with similar names have the same number of letters, as illustrated below:

In all of these cases, current flows out of the cathode and flows into the anode.

Don’t be confused by the confusion: “why does the battery have a positive cathode, but when it is charged, it becomes negative?” Remember, for all electronic elements, as well as electrolyzers and galvanics - in general, for all energy consumers, the anode is the terminal connected to the positive. This is where the differences end, now it’s easier for you to figure out what’s plus and minus between the terminals of elements and devices.

Now you know what an anode and cathode are, and how to remember them quickly enough. We hope the information provided was useful and interesting for you!

Materials

The author's greatest fear is that the inexperienced reader will not read beyond the title. He believes that the definition terms anode and cathode It is known to every literate person who, when solving a crossword puzzle, when asked about the name of the positive electrode, immediately writes the word anode and everything fits the boxes. But there are not many things worse than half-knowledge.

Recently in search engine Google in the “Questions and Answers” ​​section, I even found a rule with which its authors suggest remembering the definition of electrodes. Here it is:

« Cathode- negative electrode, anode - positive. The easiest way to remember this is to count the letters in the words. IN cathode the same number of letters as in the word “minus”, and in anode accordingly, the same as in the term “plus”.

The rule is simple, memorable, it would be necessary to offer it to schoolchildren if it were correct. Although the desire of teachers to put knowledge into the heads of students with the help of mnemonics (the science of memorization) is very commendable. But let's return to our electrodes.

First, let's take a very serious document, which is the LAW for science, technology and, of course, schools. This " GOST 15596-82. CHEMICAL CURRENT SOURCES. Terms and definitions" There on page 3 you can read the following: “The negative electrode of a chemical current source is an electrode that, when the source is discharged, anode" The same thing, “The positive electrode of a chemical current source is the electrode that, when the source is discharged, is cathode" (Terms highlighted by me. BH). But the texts of the rules and GOST contradict each other. What's the matter?

But the whole point is that, for example, a part dipped into an electrolyte for nickel plating or electrochemical polishing may be anode And cathode depending on whether another layer of metal is applied to it or, conversely, removed.

An electric battery is a classic example of a renewable chemical source of electrical current. It can be in two modes - charging and discharging. The direction of the electric current in these different cases will be in the battery itself opposite, although the polarity of the electrodes doesn't change.

Depending on this, the purpose of the electrodes will be different. When charging, the positive electrode will receive electric current and the negative electrode will release it. When discharging, it's the other way around. In the absence of movement of electric current, talk about anode And cathode are meaningless.

“Therefore, in order to avoid ambiguity and uncertainty, as well as for the sake of greater accuracy,” M. Faraday wrote in his studies in January 1834, “in the future I propose to use the terms that I will now define.”

What are the reasons for the introduction of new terms into science by Faraday?

And here they are: “Surfaces on which, according to ordinary terminology, an electric current enters and leaves a substance, are very important places of action and their must be distinguished from the poles" (Faraday. Emphasis added. BH)

In those days, after T. Seebeck’s discovery of the phenomenon of thermoelectricity, there was a popular hypothesis that the Earth’s magnetism was caused by the temperature difference between the poles and the equator, as a result of which currents arise along the equator. It was not confirmed, but served Faraday as a “ natural pointer» when creating new terms. The magnetism of the Earth has such a polarity as if an electric current were flowing along the equator in the direction of the apparent movement of the sun.

Faraday writes: “On the basis of this idea, we propose to call that surface which is directed to the east the anode, and that which is directed to the west the cathode.” The new terms were based on the ancient Greek language and when translated they meant: anode- the path (of the sun) upwards, cathode- the path (of the sun) down.

The Russian language has wonderful terms SUNRISE and SETTING, which are easy to apply for this case, but for some reason Faraday’s translators did not do this. We recommend using them, because in them the root of the word is MODE and, in any case, this will remind the user of the term that without the movement of current the term is not applicable. For those who want to check the reasoning of the creator of the term using other rules, for example, the cork bottler rule, we inform you that the north magnetic pole of the Earth lies in Antarctica, near the South Geographic Pole.

There are countless errors in the use of the terms ANODE and CATHODE. Including in foreign reference books and encyclopedias. Therefore, in electrochemistry they use other definitions that are more understandable to the reader. They have anode- this is the electrode where oxidative processes take place, and cathode- this is the electrode where reduction processes take place. In this terminology there is no place for electronic devices, but in electrical terminology it is easy to indicate the anode of a radio tube, for example. It contains electric current. (Not to be confused with electron direction).

Literature:

1. Mikhail Faraday. Experimental research on electricity. Volume 1. Publishing house of the USSR Academy of Sciences, M. 1947. p.266-268.

2. B.G. Khasapov. How to define the terms "anode" and "cathode". VNIIKI. Scientific and technical terminology. Abstract collection No. 6, Moscow, 1989, pp. 17-20.

Determining which electrode is the anode and which is the cathode seems easy at first glance. It is generally accepted that the anode has a negative charge, while the cathode has a correct charge. But in practice, there may be confusion in the definition.

Instructions

1. Anode is an electrode on which the oxidation reaction occurs. And the electrode on which the correction occurs is called the cathode.

2. Take the Jacobi-Daniel galvanic cell as an example. It consists of a zinc electrode immersed in a solution of zinc sulfate and a copper electrode in a solution of copper sulfate. The solutions come into contact with each other, but do not mix - for this purpose, a porous partition is provided between them.

3. The zinc electrode, when oxidized, gives up its electrons, which move through the external circuit to the copper electrode. Copper ions from the CuSO4 solution accept electrons and are reduced at the copper electrode. Thus, in a galvanic cell, the anode is negatively charged and the cathode is positively charged.

4. Now look at the electrolysis process. An electrolysis installation is a vessel with a solution or molten electrolyte, in which two electrodes are lowered and connected to a continuous current source. The negatively charged electrode is the cathode - correction occurs on it. The anode in this case is an electrode connected to the correct pole. Oxidation occurs on it.

5. For example, during the electrolysis of a CuCl2 solution at the anode, copper is reduced. The oxidation of chlorine occurs at the cathode.

6. Therefore, keep in mind that the anode is not always a negative electrode, just as the cathode does not have the correct charge in all cases. The factor that determines the electrode is the oxidation or reduction process occurring on it.

The diode has two electrodes called anode and cathode. It is able to conduct current from the anode to the cathode, but not vice versa. Markings explaining the purpose of the results are not available on all diodes .

Instructions

1. If there is a marking, pay attention to it appearance and location. It looks like an arrow resting on a plate. The direction of the arrow coincides with the forward direction of the current flowing through the diode. In other words, the arrow corresponds to the anode result, and the plate corresponds to the cathode result.

2. Analog multifunction meters have different polarities of voltage applied to the probes in ohmmeter mode. For some of them it is the same as in voltmeter or ammeter mode, for others it is the opposite. If it is unfamiliar to you, take a diode that is marked, switch the device to ohmmeter mode, and then connect it to the diode, first in one and then in the other polarity. If the arrow deviates, remember which diode electrode was connected to which of the probes. Now, by connecting probes in different polarities to other diodes, you will be able to determine the location of their electrodes.

3. For digital devices, in most cases, the polarity of connecting the probes is the same in all modes. Switch the multimeter to diode test mode - next to the corresponding switch location there is a designation for this part. The scarlet probe corresponds to the anode, the black one to the cathode. If the polarity is correct, the forward voltage drop across the diode will be shown, while if the polarity is incorrect, infinity will be indicated.

4. If you don't have a measuring device at hand, take a battery from motherboard, LED and one kilo-ohm resistor. Combine them in stages by connecting the LED in such a polarity that the LED glows. Now connect the diode being tested to the open circuit of this circuit, experimentally selecting such a polarity so that the LED lights up again. The diode facing the positive side of the battery is the anode.

5. If during testing it is discovered that the diode is continuously open or continuously closed, and nothing depends on the polarity, then it is faulty. Replace it, making sure in advance that its failure is not due to a malfunction of other parts. In this case, replace them first.

Pay attention!
Perform all re-soldering with de-energized equipment and discharged capacitors. Check the diode in a soldered state.

There are things that you want to, what is called “unsee” - the term is quite established and understandable.

Evgeny Grishkovets, talks about railway workers. (c) Performance “Simultaneously”

And there are things that you just can’t remember. This arises from the fact that the new concept cannot unambiguously cling to already known facts in the mind; it is impossible to construct new connection in the semantic network of facts.

Everyone knows that a diode has a cathode and an anode. Everyone knows how a diode is designated on electrical diagram. But not everyone can correctly say where on the diagram what is.

Below the spoiler is a picture, after looking at which you will forever remember where the diode is the anode and where the cathode is. I must warn you that you won’t be able to unsee this, so those who are not confident in themselves should not open it.

Now that we have scared away the weak, let's continue...

Yes, it's that simple. The letter K is the cathode, the letter A is the anode. Sorry, now you will never forget it.

Let's continue and figure out where the current flows. If you look closely, the diode designation is an arrow. Believe it or not, the current flows exactly where the arrow points! Which is logical, isn't it? Further more - the current flows" A where" (from the Anode) and " TO uda" (to the Cathode). The designations of transistors also have arrows, and they also indicate the direction of the current.

Well, the last thing is the battery. The designation is also known to everyone, two sticks are longer, thinner, and shorter, thicker. So, shorter and thicker symbolizes a minus - a kind of “fat minus” - like in school, remember: “I’ll give you four with a bold minus" This is the only way I remember, maybe someone will suggest a better option.

Now, you can easily answer the question whether the light bulb in this circuit will light up: