In which an alternator produces a sinusoidal voltage. Let's look at what happens in the circuit when we close the key. We will consider the initial moment when the generator voltage is zero.
In the first quarter of the period, the voltage at the generator terminals will increase, starting from zero, and the capacitor will begin to charge. A current will appear in the circuit, but at the first moment of charging the capacitor, despite the fact that the voltage on its plates has just appeared and is still very small, the current in the circuit (charge current) will be the greatest. As the charge on the capacitor increases, the current in the circuit decreases and reaches zero at the moment when the capacitor is fully charged. In this case, the voltage on the capacitor plates, strictly following the generator voltage, becomes at this moment maximum, but of the opposite sign, i.e., directed towards the generator voltage.
Rice. 1. Change in current and voltage in a circuit with capacitance
Thus, the current rushes with the greatest force into the charge-free capacitor, but immediately begins to decrease as the capacitor plates are filled with charges and drops to zero, fully charging it.
Let's compare this phenomenon with what happens with the flow of water in a pipe connecting two communicating vessels (Fig. 2), one of which is filled and the other empty. One has only to pull out the valve blocking the path of water, and water will immediately rush from the left vessel under high pressure through the pipe into the empty right vessel. However, immediately the water pressure in the pipe will begin to gradually weaken, due to the leveling of the levels in the vessels, and will drop to zero. The water flow will stop.
Rice. 2. The change in water pressure in the pipe connecting communicating vessels is similar to the change in current in the circuit during the charging of the capacitor
Similarly, the current first flows into an uncharged capacitor, and then gradually weakens as it charges.
With the beginning of the second quarter of the period, when the voltage of the generator begins slowly at first, and then decreases faster and faster, the charged capacitor will be discharged to the generator, which will cause a discharge current in the circuit. As the generator voltage decreases, the capacitor is discharged more and more and the discharge current in the circuit increases. The direction of the discharge current in this quarter of the period is opposite to the direction of the charge current in the first quarter of the period. Accordingly, the current curve, having passed the zero value, is now located below the time axis.
By the end of the first half-cycle, the voltage on the generator, as well as on the capacitor, quickly approaches zero, and the current in the circuit slowly reaches its maximum value. Remembering that the magnitude of the current in the circuit is greater, the greater the amount of charge transferred along the circuit, it will become clear why the current reaches its maximum when the voltage on the capacitor plates, and therefore the charge of the capacitor, quickly decreases.
With the beginning of the third quarter of the period, the capacitor begins to charge again, but the polarity of its plates, as well as the polarity of the generator, changes to the opposite, and the current, continuing to flow in the same direction, begins to decrease as the capacitor is charged. At the end of the third quarter of the period, when the voltages across the generator and capacitor reach their maximum, the current becomes zero.
In the last quarter of the period, the voltage, decreasing, drops to zero, and the current, changing its direction in the circuit, reaches its maximum value. This ends the period, after which the next one begins, exactly repeating the previous one, etc.
So, under the influence of alternating voltage from the generator, the capacitor is charged twice per period (the first and third quarters of the period) and discharged twice (the second and fourth quarters of the period). But since alternating one after another is accompanied each time by the passage of charging and discharging currents through the circuit, we can conclude that .
You can verify this using the following simple experiment. Connect a capacitor with a capacity of 4-6 microfarads to the AC network through a 25 W electric light bulb. The light will light up and will not go out until the circuit is broken. This indicates that alternating current passed through the circuit with the capacitance. However, it passed, of course, not through the dielectric of the capacitor, but at each moment of time it represented either the charge current or the discharge current of the capacitor.
The dielectric, as we know, is polarized under the influence of the electric field that arises in it when the capacitor is charged, and its polarization disappears when the capacitor is discharged.
In this case, the dielectric with the bias current arising in it serves as a kind of continuation of the circuit for alternating current, and breaks the circuit for direct current. But the displacement current is generated only within the dielectric of the capacitor, and therefore no through charge transfer through the circuit occurs.
The resistance provided by a capacitor to alternating current depends on the value of the capacitor's capacitance and the frequency of the current.
The larger the capacitor's capacitance, the greater the charge transferred through the circuit during the charging and discharging of the capacitor, and therefore, the greater the current in the circuit. An increase in current in the circuit indicates that its resistance has decreased.
Hence, As the capacitance increases, the resistance of the circuit to alternating current decreases.
An increase increases the amount of charge transferred through the circuit, since the charge (as well as the discharge) of the capacitor must occur faster than at a low frequency. At the same time, an increase in the amount of charge transferred per unit time is equivalent to an increase in the current in the circuit, and, consequently, a decrease in its resistance.
If we somehow gradually reduce the frequency of the alternating current and reduce the current to constant, then the resistance of the capacitor connected to the circuit will gradually increase and become infinitely large (open circuit) by the time it appears.
Hence, As the frequency increases, the capacitor's resistance to alternating current decreases.
Just as the resistance of a coil to alternating current is called inductive, the resistance of a capacitor is usually called capacitive.
Thus, The capacitance is greater, the lower the capacitance of the circuit and the frequency of the current supplying it.
Capacitance is denoted by Xc and measured in ohms.
The dependence of capacitance on current frequency and circuit capacitance is determined by the formula Xc = 1/ωС, where ω - circular frequency equal to the product of 2π f, C-capacitance of the circuit in farads.
Capacitive reactance, like inductive reactance, is reactive in nature, since the capacitor does not consume the energy of the current source.
The formula for a circuit with capacitance is I = U/Xc, where I and U are the effective values of current and voltage; Xc is the capacitance of the circuit.
The property of capacitors to provide high resistance to low-frequency currents and easily pass high-frequency currents is widely used in communication equipment circuits.
With the help of capacitors, for example, the separation of direct currents and low-frequency currents from high-frequency currents necessary for the operation of circuits is achieved.
If it is necessary to block the path of low-frequency current into the high-frequency part of the circuit, a small capacitor is connected in series. It offers great resistance to low-frequency current and at the same time easily passes high-frequency current.
If it is necessary to prevent high-frequency current, for example, from entering the power circuit of a radio station, then a large capacitor is used, connected in parallel with the current source. In this case, the high-frequency current passes through the capacitor, bypassing the power supply circuit of the radio station.
Active resistance and capacitor in an alternating current circuit
In practice, there are often cases when a circuit is in series with a capacitance. The total resistance of the circuit in this case is determined by the formula
Hence, the total resistance of a circuit consisting of active and capacitive resistance to alternating current is equal to the square root of the sum of the squares of the active and capacitive resistance of this circuit.
Ohm's law remains valid for this circuit I = U/Z.
In Fig. Figure 3 shows curves characterizing the phase relationships between current and voltage in a circuit containing capacitive and active resistance.
Rice. 3. Current, voltage and power in a circuit with a capacitor and active resistance
As can be seen from the figure, the current in this case leads the voltage not by a quarter of a period, but less, since the active resistance has violated the purely capacitive (reactive) nature of the circuit, as evidenced by the reduced phase shift. Now the voltage at the circuit terminals will be determined as the sum of two components: the reactive component of the voltage u c, which goes to overcome the capacitance of the circuit, and the active component of the voltage, which overcomes its active resistance.
The greater the active resistance of the circuit, the smaller the phase shift will be between current and voltage.
The power change curve in the circuit (see Fig. 3) twice during the period acquired a negative sign, which is, as we already know, a consequence of the reactive nature of the circuit. The less reactive the circuit, the smaller the phase shift between current and voltage and the more power the current source consumes.
A capacitor, conder, air conditioner - this is what experienced specialists call it - one of the most common elements used in various electrical circuits. A capacitor is capable of storing an electric current charge and transferring it to other elements in an electrical circuit.
The simplest capacitor consists of two plate electrodes separated by a dielectric; an electric charge of different polarity accumulates on these electrodes; one plate will have a positive charge and the other will have a negative charge.
The principle of operation of a capacitor and its purpose- I will try to answer these questions briefly and very clearly. In electrical circuits, these devices can be used for various purposes, but their main function is to store electrical charge, that is, a capacitor receives electric current, stores it and subsequently transfers it to the circuit.
When a capacitor is connected to an electrical network, an electrical charge begins to accumulate on the electrodes of the capacitor. At the beginning of charging, the capacitor consumes the greatest amount of electric current; as the capacitor is charged, the electric current decreases and when the capacitor’s capacity is filled, the current will disappear completely.
When the electrical circuit is disconnected from the power source and a load is connected, the capacitor stops receiving charge and transfers the accumulated current to other elements, itself, as it were, becoming a power source.
The main technical characteristic of a capacitor is its capacity. Capacitance is the ability of a capacitor to accumulate electrical charge. The larger the capacitance of the capacitor, the more charge it can accumulate and, accordingly, release back into the electrical circuit. The capacitance of a capacitor is measured in Farads. Capacitors vary in design, materials from which they are made and areas of application. The most common capacitor is - constant capacitor, it is designated as follows:
Constant-capacity capacitors are made from a wide variety of materials and can be metal-paper, mica, or ceramic. Such capacitors as an electrical component are used in all electronic devices.
Electrolytic capacitor
The next common type of capacitors is polar electrolytic capacitors, its image on the electrical diagram looks like this -
An electrolytic capacitor can also be called a permanent capacitor because its capacitance does not change.
But eh electrolytic capacitors have a very important difference, the (+) sign near one of the electrodes of the capacitor indicates that this is a polar capacitor and when connecting it to the circuit, polarity must be observed. The positive electrode must be connected to 
the plus of the power source, and the negative (which does not have a plus sign) correspondingly to the negative - (on the body of modern capacitors the designation of the negative electrode is applied, but the positive electrode is not designated in any way).
Failure to follow this rule can lead to capacitor failure and even an explosion, accompanied by scattering of foil paper and a bad smell (from the capacitor, of course...). Electrolytic capacitors can have a very large capacity and, accordingly, accumulate quite a large potential. Therefore, electrolytic capacitors are dangerous even after the power is turned off, and if handled carelessly, you can receive a strong electric shock. Therefore, after removing the voltage, for safe work with an electrical device (electronics repair, setup, etc.), the electrolytic capacitor must be discharged by short-circuiting its electrodes (this must be done with a special discharger), especially for large capacitors that are installed on power supplies where there is high voltage.
Variable capacitors.
As you understand from the name, variable capacitors can change their capacitance - for example, when tuning radio receivers. More recently, only variable capacitors were used to tune radio receivers to the desired station; rotating the receiver tuning knob thereby changed the capacitance of the capacitor. Variable capacitors are still used today in simple, inexpensive receivers and transmitters. The design of a variable capacitor is very simple. Structurally, it consists of stator and rotor plates, the rotor plates are movable and enter the stator plates without touching the latter. The dielectric in such a capacitor is air. When the stator plates enter the rotor plates, the capacitance of the capacitor increases, and when the rotor plates exit, the capacitance decreases. The designation of a variable capacitor looks like this -
APPLICATION OF CAPACITORS
Capacitors are widely used in all areas of electrical engineering; they are used in various electrical circuits.
In an alternating current circuit they can serve as capacitance. Let's take this example: when a capacitor and a light bulb are connected in series to a battery (direct current), the light bulb will not light up.
If you connect such a circuit to an alternating current source, the light bulb will glow, and the intensity of the light will directly depend on the value of the capacitance of the capacitor used. 
Thanks to these qualities, capacitors are used as filters in circuits that suppress high-frequency and low-frequency interference.
Capacitors are also used in various pulse circuits where the rapid accumulation and release of a large electrical charge is required, in accelerators, photo flashes, pulsed lasers, due to the ability to accumulate a large electrical charge and quickly transfer it to other elements of the network with low resistance, creating a powerful pulse.Capacitors are used to smooth out ripples during voltage rectification. The ability of a capacitor to retain a charge for a long time makes it possible to use them for storing information. And this is only a very short list of everything where a capacitor can be used.
As you continue your studies in electrical engineering, you will discover many more interesting things, including the work and use of capacitors. But this information will be enough for you to understand and move forward.
How to check a capacitor
To check capacitors you need a device, tester or otherwise multimeter. There are special devices that measure capacitance (C), but these devices cost money, and there is often no point in purchasing them for a home workshop, especially since there are inexpensive Chinese multimeters on the market with a capacitance measurement function. If your tester does not have such a function, you can use the usual dialing function - to how to ring with a multimeter, as when checking resistors - what is a resistor. The capacitor can be checked for “breakdown”; in this case, the resistance of the capacitor is very large, almost infinite (depending on the material from which the capacitor is made). Electrolytic capacitors are checked as follows - It is necessary to turn on the tester in the continuity mode, connect the probes of the device to the electrodes (legs) of the capacitor and monitor the reading on the multimeter indicator, the multimeter reading will change downward until it stops completely. After which you need to swap the probes, the readings will begin to decrease almost to zero. If everything happened as I described, the Conder is working. If there is no change in the readings or the readings immediately become large or the device shows zero, the capacitor is faulty. Personally, I prefer to check the “air conditioners” with a dial gauge; the smooth movement of the needle is easier to track than the flashing of numbers in the indicator window.
Capacitor capacity measured in Farads, 1 farad is a huge value. Such a capacity will have a metal ball whose dimensions will exceed the size of our sun by 13 times. A sphere the size of planet Earth would have a capacity of only 710 microfarads. Typically, the capacitance of capacitors that we use in electrical devices is indicated in microfarads (mF), picofarads (nF), nanofarads (nF). You should know that 1 microfarad is equal to 1000 nanofarads. Accordingly, 0.1 uF is equal to 100 nF. In addition to the main parameter, the permissible deviation of the actual capacity from the specified one and the voltage for which the device is designed are indicated on the body of the elements. If it is exceeded, the device may fail.
This knowledge will be enough for you to start and to independently continue studying capacitors and their physical properties in special technical literature. I wish you success and perseverance!
People who are far from technology do not even think that the design of modern electrical appliances contains various elements that make this equipment work. They don’t even understand what they’re talking about when the experts around them talk about technology. But sometimes curiosity gets the better of them and they start asking questions. For example, why do you need a capacitor?
To satisfy curiosity, we will try to explain its functions and identify in which areas capacitors have found their application.
What is a capacitor?
A capacitor, popularly known as “conder,” is a device that is used in electrical circuits to store electrical energy. Capacitors are used in noise filtering, in smoothing filters in power supplies, interstage communication circuits, and in many other areas of radio engineering.
The design and materials used determine the electrical characteristics of the Conder. The capacitor device includes plates (or plates) located in front of each other. They are made from conductive and insulating material. Mica or paper can be used as insulation.
The capacitance of a capacitor may vary. It increases in size in proportion to the area of the plates, and its decrease occurs depending on the distance between them. The operating voltage of the capacitor is very important. If the maximum voltage is exceeded, the capacitor may break due to dielectric breakdown.
How it all began
The principle of manufacturing this device was known for quite a long time, thanks to the German physicist Ewald Jurgen von Kleist and his Dutch colleague Peter van Musschenbroeck. They were the creators of the world's first capacitor. Their brainchild was much more primitive than its modern counterparts, because the walls of the glass jar acted as a dielectric. Nowadays, technology is much more advanced, and the creation of new materials has greatly improved the design of the capacitor.
The brilliant electrical engineer Pavel Yablochkov was also able to achieve outstanding results in the development of capacitors and their use. He created many publications on this topic. Pavel Nikolaevich understood perfectly why do you need a capacitor , therefore, he was one of the first to include the “conder” in the alternating current circuit. This was of great importance for the development and establishment of electrical and radio engineering.
There are a variety of capacitors available these days, but they all rely on two metal plates that are insulated from each other.
Where are capacitors used?
Capacitors surround us in many areas, occupying a special niche in electronics.
- Television or radio equipment cannot do without capacitors. They are used for rectifier filters, creating and tuning oscillatory circuits, separating circuits with different frequencies, and much more.
- Radar technology uses them to produce higher power pulses and also to shape the pulses.
- For spark extinguishing in contacts, separation of currents of different frequencies, separation of direct and alternating current circuits, “conders” are needed in telegraphy and telephony.
- In telemechanics and automation, they are used to create sensors based on the capacitive principle. Here you also need spark extinguishing in contacts, separation of current circuits, etc.
- In special storage devices that are used in computing technology.
- For obtaining powerful pulses in laser technology.
Modern electric power industry also uses this entire invention: to connect the necessary equipment to the transmission line in order to increase the power factor, to regulate voltage in distribution networks, to protect against overvoltage, for electric welding, suppression of radio interference and much more.
Why do you need a capacitor? more? For the metal industry, automotive and medical equipment, for the use of atomic energy, in photographic technology for producing light flashes and aerial photography. Even the mining industry cannot do without capacitors. Some capacitors can be very tiny and weigh less than one gram, while their other “comrades” weigh several tons and are more than two meters high.
A huge variety of types of capacitors has made it possible to use them in various fields of activity, so we cannot do without them.
A capacitor is a passive electronic component that has two poles with a fixed or variable capacitance value. It also has low conductivity. It is important to understand why a capacitor is needed in an electric motor, because according to the information presented on the forums, many people have the wrong idea about this and simply underestimate the importance of this device.
What is a capacitor used for?
The device is used in all electrical and radio circuits. For what purposes is a capacitor included in the circuit:
- Acts as a resistance, which allows it to be used as a filter to suppress high-frequency and low-frequency interference.
- They are used for photo flashes and lasers, and all thanks to the device’s ability to accumulate charge and quickly discharge, creating a pulse.
- Helps compensate for reactive energy, allowing it to be used in industry.
- Thanks to the ability to accumulate and retain charge for a long time, a capacitor can be used to store information and power low-power devices.
What is a car capacitor used for?
This device can perform several functions in the car. For example, they are used to create high voltage levels throughout the entire electrical system in a car. Most often, a capacitor is used for car acoustics. Speaking about why condensates are needed in car audio, we note that its main purpose is to help the amplifier quickly deliver the available power at low frequency peaks.
If a capacitor is not used in the speaker system, then the bass sound will not be as clear, and there may also be a drawdown in the power supply to the entire electrical network of the car. Such power surges can ultimately lead to the subwoofer simply breaking down.
When choosing a capacitor for a car, follow the rule that there should be 1 F per 1 kW of power. Choose high-quality capacitors and it is best if they have charge control capabilities.
It's also worth figuring out how to properly install the capacitor. It is best to do this as close as possible to the subwoofer amplifier, since this is where the heaviest load is placed. The distance should not be more than 60 cm. Connection type – parallel.
Why is a capacitor needed in an electric motor?
For some motors to operate properly, it is necessary to use a starting and running capacitor. The main purpose of the starting capacitor is to improve the starting performance of the engine. This device helps reduce the time it takes for the engine to enter its operating mode, while increasing torque and facilitating the engine starting process.
As for the working capacitor, it is involved in work throughout the entire operating time of the engine. This device ensures the heating of the windings permissible by standards, optimal load capacity and efficiency of the electric motor. He's also 
Helps maximize torque and increase engine life.
Now you need to find out which capacitor is needed for the motor. The capacitance of this device is usually selected on the basis that there should be 6.6 mF per 100 W. Sometimes this value is incorrect, so it is best to select the capacity through experimentation. There are several selection methods, but the most accurate values can be obtained by connecting the motor through an ammeter. It is important to control the current consumption at different capacities. The task is to find at what capacitance the current value on the ammeter will be minimal.
Capacitors perform many useful functions in electronic device circuits despite their simple design. If you disassemble several radio-electronic devices to detail and count them, it turns out that the number of elements discussed in this article will exceed the number of other individual radio-electronic devices, including. In view of this circumstance, we should pay special attention to the design, structure and principle of operation of capacitors.
Operating principle of a capacitor
To better understand the principle of operation of a capacitor, consider its design. The simplest capacitor consists of two metal plates called plates. Between the plates there is a dielectric, that is, a substance that practically does not allow electric current to pass through. The covers, as a rule, have the same geometric dimensions (square, rectangle, circle) and are equal in area. The plates are made of aluminum, copper or precious metals. The presence of precious metals in the composition of the plates causes an increased hunt on radio markets for Soviet samples of this radio-electronic element.
Dry paper, ceramics, porcelain, air, etc. are used as a dielectric located between the plates.
The principle of operation of a capacitor is as follows. If one plate is connected to the plus of an electric current source, and the second to the minus, then both plates will be charged with opposite charges. Charges will continue to be held on the plates even after the power source is disconnected. This is explained by the fact that charges of different signs (“+” and “-”) tend to attract each other. However, this is prevented by a dielectric (material that does not conduct charges) located in their path. Therefore, the charges distributed over the entire area of the plates remain in their places and are held by forces of mutual attraction.
Dielectric polarization
This phenomenon is called the accumulation of electrical charges. And a capacitor is called an electric field accumulator, since an electric field acts around each charge, under the influence of which the dielectric is polarized, that is, its molecules become polar - they have clearly defined positive and negative poles. The poles of the molecules of a non-conducting substance are oriented along the lines of the electric field created by the charges located on the plates. Moreover, the negative pole of the molecule is directed towards the positive plate, and the positive pole - towards the negative one.
The ability to accumulate electrical charges is characterized by the capacitance of a capacitor, hence its designation on electrical circuit drawings C (English) c apacitor – storage device). Similar to the capacity of a vessel - the larger the capacity of the vessel, the more liquid it can hold.
The capacitance of the capacitor refers to the main parameter and is measured in farads [F ], named after the outstanding English physicist Michael Faraday.
Please note: it is correct to say not “one farad”, but “one farad”.
A capacitor has a capacitance of one farad, which accumulates a charge of , if a voltage of one volt is applied to the plates.
Previously, one could often hear the statement that the capacity in 1 F– this is a lot – almost the capacity of our planet. However, now, with the advent of supercapacitors, they no longer say this, since the capacity of the latter reaches hundreds of farads. However, most electronic circuits use smaller storage devices. C – picofarads, nanofarads and microfarads.
Capacitor capacitance calculation
Calculating the capacitance of capacitors is quite simple. It is determined by three parameters: plate area S , distance between plates d and type of dielectric ε :
The physical meaning of this formula is as follows: the larger the area of the plates, the more charges can be located (accumulated) on it; The greater the distance between the plates and, accordingly, between the charges, the lower the force of their mutual attraction - the weaker they are held on the plates, so it is easier for the charges to leave the plates, which leads to a decrease in their number, and therefore a decrease in the capacity of the electric field storage device.
The dielectric constant ε shows how many times the charge of a capacitor with a given dielectric exceeds the charge of a similar storage device if there is a vacuum between its plates of the same area and located at the same distance. For air ε equal to one, that is, practically no different from vacuum. Dry paper has a dielectric constant twice that of air; porcelain - four and a half times ε = 4.5. Capacitor ceramics have ε = 10..200 units.
An important conclusion follows from this: in order to obtain maximum capacity while maintaining the same geometric dimensions, a dielectric with maximum dielectric constant should be used. Therefore, ceramics are used in widely used flat-plate capacitors.
Capacitor in DC and AC circuits
Since there is a dielectric between the plates of the capacitor, electric current cannot flow from one plate to another, therefore, an open circuit is formed for direct and alternating current. Therefore, we can confidently say that the capacitor does not allow direct current to pass through! It also does not allow alternating current to pass through, but the alternating current constantly recharges the storage device, which creates the picture of alternating current passing through the plates of the capacitor.
If a constant voltage is applied to the plates of a discharged capacitor, an electric current will begin to flow in the circuit. As it charges, the current will decrease and if the voltages on the plates and the power source are equal, the current will stop flowing - a break in the electrical circuit will form.
Fixed capacitors
The capacity of such capacitors is not intended to be changed during the operation of radio-electronic equipment. They are distinguished by the widest variety and geometric sizes - from a match head to huge cabinets and are most widely used in printed circuit boards of electronic devices. The most common specimens are shown in the photo.
Variable capacitors KPE
To change the capacitance of a separate unit of an electrical circuit directly during operation of an electronic device, variable capacitors (VCA) are used. KPIs were mainly used in old-style receivers to tune the oscillating circuit to the resonant frequency of the radio station. However, now, instead of KPIs, varicaps are used - semiconductor diodes, the capacitance of which is determined by the value of the supplied reverse voltage. Now it is enough to change the voltage supplied to the varicap to change the capacitance of the latter, and as a result, the frequency of the oscillatory circuit.
As a rule, KPI consists of a number of parallel metal plates separated by air, so their dimensions are very significant. Varicaps, on the contrary, have much smaller dimensions, which is why they replaced the KPE.
Trimmer capacitors are used in final tuning units of electronic equipment. Most often they are found in various kinds of oscillatory circuits or in devices related to frequency formation; in measuring instruments. They can also be found in digital oscilloscope probes. There they are used to eliminate the intrinsic capacitance of the measuring probes, which makes it possible to eliminate errors as much as possible when performing measurements of high-frequency signals.
The main difference and advantage of electrolytic capacitors is their large capacity with small dimensions. Due to this property, they are widely used as electrical filters to smooth out rectified voltage, which makes them an integral part of any power supply.
Structurally, the electrolytic capacitor is made of aluminum foil, which serves as one of the plates. The foil is wound into a roll in the form of a cylinder, which allows you to increase the active area of the lining. An oxide layer is applied to the foil, which is a dielectric. The second plate is an electrolyte or semiconductor layer. For this reason, electrolytic capacitors are polar (non-polar ones are used much less frequently), that is, polarity must be observed when connecting them to the circuit. Otherwise, it will fail, most often it will explode. Therefore, you should be extremely careful when connecting such a radio-electronic element to an electrical circuit, which is often forgotten to do when replacing this component.
The negative terminal of the new electrolytic capacitor is shorter than the positive one, and the corresponding minus sign is applied to the housing next to it. In Soviet marking, on the contrary, the positive terminal is marked, on the side of which a “+” sign is applied to the housing.
Also, the housings of electrolytic capacitors must contain the values of three main parameters: nominal capacity value , maximum permissible voltage and maximum operating temperature .
If everything is clear with the capacity and permissible temperature, then special attention should be paid to the voltage.
An electrolytic capacitor must not be supplied with a voltage greater than that indicated on the housing. . Otherwise it will explode. Most developers of electronic equipment advise not to exceed the voltage on the plates more than 80% of the permissible value.
Designation of capacitors in circuits
In electrical diagram drawings, the designation of capacitors is strictly standardized. However, this radio-electronic element can always be recognized in the circuit by two parallel, adjacent vertical lines. Two vertical lines indicate two facings. These dashes are signed with a Latin letter C , next to which the serial number of the element in the circuit is indicated, and below or on the side the capacitance value in microfarads or picofarads is indicated.
Capacitor markings
As electronics develops, so does the element base. Since many countries produce their own radio-electronic elements, their markings differ from the markings of radio-electronic elements in other countries. Therefore, in the first stages of industrial electronics production, many different types of marking were used, but the desire for unification led to more or less streamlining. This made it possible to bring the marking of capacitors to general rules. And the advantage here is obvious - a radio-electronic element produced in one country can now quite easily be matched with an analogue produced in another country. It would be ideal to reduce all types of designations and markings to a single type, which has already been almost completely accomplished.
However, Soviet capacitors, distinguished by a small but varied marking, are still in wide circulation. Everything was involved in Soviet markings - numbers, letters and colors. Moreover, both numbers and letters, as well as colors, numbers and letters, were applied to the housings of the elements. The numbers indicate the value, the letters indicate the units of measurement.
The more common type of marking consists of numbers that indicate the capacity in pico farads , not to be confused with farads! You should always remember that, unlike resistors, which are marked in ohms, the basic dimension, regardless of the marking method, is pico farads (if the numbers are separated by a comma, then micro farads ). In general, the capacitance count starts from picofarad .
Also, previously only color marking was used - a solid color with a colored dot. The parameters can only be determined using the reference book.
The types of markings discussed above are gradually going out of use, but they are always remembered by specialists who repair Soviet equipment in which radioelements have the “old” designation.
The most successful and perfect way to designate electronic elements is digital coding. Digital coding of capacitors, like resistors, involves the use of only three digits. This approach allows for many combinations to be implemented. The two digits on the left indicate the mantissa, that is, the significant number, and the last - third digit shows how many zeros need to be added to the previous two digits. For example, if the drive case indicates 153 , then its capacity is equal 15 ×10 3 = 15000 pF = 15 nF = 0.015 µF.
In addition to capacity, drives are characterized by a number of basic parameters, which are discussed below.
Marking SMD capacitors
The marking of SMD capacitors can be applied to the case in the form of digital coding, but in the vast majority it is a somewhat confusing encryption consisting of one or two letters of the Latin alphabet. If there are two letters, then the first one indicates the manufacturer, which interests us to a lesser extent. But the second or only letter denotes the mantissa, in the same way as in digital coding. The remaining digit shows the number of zeros after the mantissa. You can decipher the digital value of a letter using the table below.
SMD drives with similar characteristics also differ in size. A number of standard sizes are shown in the table and figure below. It is especially important to take into account the dimensions of radio-electronic elements when designing printed circuit boards.
The marking of electrolytic SMD capacitors is practically no different from their output counterparts. A negative pad is indicated by a black mark on the flat side of the housing on the side of the corresponding pad. The permissible voltage in volts and capacitance in microfarads are also indicated.
Quite often there are cases that do not have any markings on them. Only a capacitance meter can help here.
Series connection of capacitors
Connecting capacitors in series allows you to apply a higher voltage to their plates than to a separate storage device. The voltage on the plates is distributed depending on the capacitance of the element.
If two drives have the same capacity, then the supplied voltage is distributed equally between them. However, the total capacity will be half that of a separate drive.
In general, the rule to remember is that when capacitors are connected in series together, they can withstand higher voltages, but this comes at the cost of reduced capacitance.
Parallel connection of capacitors
This connection method is the most common in practical applications, since the capacity of one drive is not always enough, especially in electrical filters of high-quality power supplies. Parallel connection of capacitors realizes the summation of the capacitances of individual storage devices. This is quite easy to remember, based on the formula above, which shows that as the area of the plates increases, the capacitance increases. 
Therefore, when connecting capacitors in parallel, there is a kind of increase in the area of the plates, due to which they are able to accumulate a larger number of electrical charges.
The main parameters and ratings of capacitors are discussed here.
