Download the presentation on the topic types of capacitors. Types of capacitors

Slide 14

What is the electrical capacity of the capacitor if the charge of the capacitor is 10 nC and the potential difference is 20 kV. And now the task...

Slide 15

A 10 µF capacitor was given a charge of 4 µC. What is the energy of a charged capacitor. And now the task...

Capacitors general purpose– capacitors used in most types of electronic equipment. No special requirements apply to capacitors of this type. Special purpose capacitors are all other capacitors. These include: pulse, high-voltage, starting, noise suppression, as well as other capacitors.

Fixed capacitors are capacitors whose capacitance is fixed and does not change during operation of the equipment. Variable capacitors - used in circuits where capacitance changes during operation are required. In this case, the capacitance can be changed in various ways: mechanically, by changing the control voltage, by changing the ambient temperature.

Unprotected capacitors are a type of capacitors that are not allowed to operate in conditions of high humidity. It is possible to operate these capacitors as part of sealed equipment. Protected capacitors - can operate in conditions of high humidity.

Non-insulated capacitors - when using this type of capacitors, they are not allowed to touch the equipment chassis with their housing. Insulated capacitors - have a well-insulated housing, which makes it possible to touch the equipment chassis or its live surfaces. Sealed capacitors - this type of capacitor uses a housing sealed with organic materials. Sealed capacitors - These capacitors have a sealed housing, which eliminates the interaction of the internal structure of the capacitor with the environment.

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Types of capacitors and their applications.

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A capacitor is a device for storing charge. One of the most common electrical components. There are many different types capacitors, which are classified according to various properties.

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Basically, the types of capacitors are divided: According to the nature of the change in capacitance - constant capacitance, variable capacitance and tuning. According to the dielectric material - air, metallized paper, mica, Teflon, polycarbonate, oxide dielectric (electrolyte). According to the installation method - for printed or mounted mounting.

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Ceramic capacitors.

Ceramic capacitors or ceramic disk capacitors are made of a small ceramic disk coated on both sides with a conductor (usually silver). Due to their fairly high relative dielectric constant (6 to 12), ceramic capacitors can accommodate quite a large capacitance in a relatively small physical size.

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Film capacitors.

The capacitance of the capacitor depends on the area of ​​the plates. In order to compactly accommodate a large area, film capacitors are used. The principle of “multi-layering” is used here. Those. create many layers of dielectric, alternating layers of plates. However, from an electrical point of view, these are the same two conductors separated by a dielectric, like a flat ceramic capacitor.

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Electrolytic capacitors.

Electrolytic capacitors are usually used when large capacitance is required. The design of this type of capacitor is similar to that of film capacitors, only here instead of a dielectric, special paper impregnated with electrolyte is used. The capacitor plates are made of aluminum or tantalum.

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Tantalum capacitors.

Tantalum capacitors are physically smaller than their aluminum counterparts. In addition, the electrolytic properties of tantalum oxide are better than aluminum oxide - tantalum capacitors have significantly less current leakage and higher capacitance stability. The range of typical capacitances is from 47nF to 1500uF. Tantalum electrolytic capacitors are also polar, but they tolerate incorrect polarity connections better than their aluminum counterparts. However, the range of typical voltages for tantalum components is much lower - from 1V to 125V.

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Variable capacitors.

Variable capacitors are widely used in devices where adjustments are often required during operation - receivers, transmitters, measuring instruments, signal generators, audio and video equipment. Changing the capacitance of the capacitor allows you to influence the characteristics of the signal passing through it.

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Trimmer capacitors.

Trimmer capacitors are used for one-time or periodic capacitance adjustment, in contrast to “standard” variable capacitors, where the capacitance changes in “real time”. This adjustment is intended for the equipment manufacturers themselves, and not for its users, and is performed with a special adjusting screwdriver. A regular steel screwdriver is not suitable as it may affect the capacitance of the capacitor. The capacity of tuning capacitors is usually small - up to 500 picoFarads.

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Application of capacitors.

An important property of a capacitor in an alternating current circuit is its ability to act as capacitive reactance (inductive in the coil). If you connect a capacitor and a light bulb in series to a battery, it will not light up. But if you connect it to an AC source, it will light up. And the higher the capacitance of the capacitor, the brighter it will glow. Due to this property, they are widely used as a filter, which can quite successfully suppress HF and LF interference, voltage ripple and AC surges.

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Thanks to the ability of capacitors for a long time accumulate a charge and then quickly discharge in a circuit with low resistance to create a pulse, making them indispensable in the production of photo flashes, electromagnetic-type accelerators, lasers, etc. Capacitors are used when connecting a 380 to 220 Volt electric motor. It is connected to the third terminal, and due to the fact that it shifts the phase by 90 degrees on the third terminal, it becomes possible to use a three-phase motor in a single-phase 220 Volt network. In industry, capacitor units are used to compensate reactive energy.

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The ability of a capacitor to accumulate and store electric charge on for a long time, made it possible to use it in elements to store information. And also as a power source for low-power devices. For example, an electrician's probe, which you just need to insert into a socket for a couple of seconds until the built-in capacitor in it is charged, and then you can ring circuits all day long with its help. But unfortunately, the capacitor is significantly inferior in its ability to store electrical energy from a battery due to leakage currents (self-discharge) and the inability to accumulate large amounts of electrical energy.

Description of the presentation by individual slides:

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MINISTRY OF EDUCATION AND SCIENCE OF THE RF GBPOU "Technological College named after. N.D. Kuznetsova" SPECIALTY INFORMATION SYSTEMS Presentation on physics on the topic: "Capacitors" Prepared by: 1st year student Victoria Sergeevna Vidyasova Scientific supervisor: Olga Vasilievna Kurochkina Samara, 2016.

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Introduction: Definition Types of capacitors Marking of capacitors Application of capacitors

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DEFINITION A capacitor is an electrical (electronic) component constructed from two conductors (plates) separated by a dielectric layer. There are many types of capacitors and they are mainly divided according to the material of the plates themselves and the type of dielectric used between them.

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Types of capacitors Paper and metal capacitors In a paper capacitor, the dielectric separating the foil plates is special capacitor paper. In electronics, paper capacitors can be used in both low-frequency and high-frequency circuits. Sealed metal-paper capacitors, which instead of foil (as in paper capacitors) use vacuum deposition of metal onto a paper dielectric, have good quality electrical insulation and increased specific capacitance. A paper capacitor does not have great mechanical strength, so its filling is placed in a metal case, which serves as the mechanical basis of its design.

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Electrolytic capacitors In electrolytic capacitors, unlike paper capacitors, the dielectric is a thin layer of metal oxide formed electrochemically on a positive cover of the same metal. The second cover is a liquid or dry electrolyte. The material that creates the metal electrode in an electrolytic capacitor can be, in particular, aluminum and tantalum. Traditionally, in technical jargon, “electrolyte” refers to aluminum capacitors with a liquid electrolyte. But, in fact, tantalum capacitors with solid electrolyte also belong to electrolytic capacitors (they are less common with liquid electrolyte). Almost all electrolytic capacitors are polarized, and therefore they can only operate in DC voltage circuits while maintaining polarity. In case of polarity reversal, an irreversible chemical reaction may occur inside the capacitor, leading to the destruction of the capacitor, even to its explosion due to the gas released inside it. Electrolytic capacitors also include the so-called supercapacitors (ionistors) with an electrical capacity that sometimes reaches several thousand Farads.

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Aluminum Electrolytic Capacitors Aluminum is used as the positive electrode. The dielectric is a thin layer of aluminum trioxide (Al2O3), Properties: they work correctly only at low frequencies have a large capacitance Characterized by a high capacitance-to-size ratio: electrolytic capacitors are usually large in size, but capacitors of a different type, the same capacitance and breakdown voltage would be much larger in size. They are characterized by high leakage currents and have moderately low resistance and inductance.

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Tantalum electrolytic capacitors This is a type of electrolytic capacitor in which the metal electrode is made of tantalum and the dielectric layer is made of tantalum pentoxide (Ta2O5). Properties: high resistance to external influences, compact size: for small ones (from several hundred microfarads), size comparable to or smaller than aluminum capacitors with the same maximum breakdown voltage, lower leakage current compared to aluminum capacitors.

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Polymer capacitors Unlike conventional electrolytic capacitors, modern solid-state capacitors have a polymer dielectric instead of an oxide film used as a plate separator. This type of capacitor is not subject to swelling and charge leakage. The physical properties of the polymer contribute to the fact that such capacitors are characterized by high pulse current, low equivalent resistance and a stable temperature coefficient even at low temperatures. Polymer capacitors can replace electrolytic or tantalum capacitors in many circuits, such as filters for switching power supplies, or in DC-DC converters.

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Film capacitors In this type of capacitor, the dielectric is a plastic film, for example, polyester (KT, MKT, MFT), polypropylene (KP, MKP, MFP) or polycarbonate (KC, MKC). Electrodes can be deposited on this film (MKT, MKP, MKC) or made in the form of a separate metal foil, wound into a roll or pressed together with a dielectric film (KT, KP, KC). The modern material for capacitor film is polyphenylene sulfide (PPS). General properties of film capacitors (for all types of dielectrics): they work properly at high current have high tensile strength have a relatively small capacitance minimum leakage current used in resonant circuits and RC snubbers Individual types of film differ in: temperature properties (including with the sign temperature coefficient of capacity, which is negative for polypropylene and polystyrene, and positive for polyester and polycarbonate) maximum operating temperature (from 125 °C, for polyester and polycarbonate, up to 100 °C for polypropylene and 70 °C for polystyrene) resistance to electrical breakdown , and therefore the maximum voltage that can be applied to a certain film thickness without breakdown.

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Ceramic capacitors This type of capacitors is made in the form of one plate or a pack of plates from a special ceramic material. Metal electrodes are sprayed onto the plates and connected to the terminals of the capacitor. The ceramic materials used can have very different properties. The diversity includes, first of all, a wide range of relative electrical permeability values ​​(up to tens of thousands, and this value is found only in ceramic materials). Such a high permeability value allows the production of ceramic capacitors (multilayer) of small sizes, the capacitance of which can compete with the capacitance of electrolytic capacitors , and at the same time working with any polarization and characterized by less leakage. Ceramic materials are characterized by a complex and nonlinear dependence of parameters on temperature, frequency, and voltage. Due to the small size of the case, this type of capacitor has a special marking.

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How are large capacitors marked? To correctly read the technical specifications of a device, some preparation is necessary. You need to start studying with units of measurement. To determine capacitance, a special unit is used - farad (F). The value of one farad for a standard circuit seems too large, so household capacitors are marked in smaller units of measurement. The most commonly used is mF = 1 µF (microfarad), which is 10-6 farads.

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When calculating, an off-label unit can be used - millifarad (1mF), which has a value of 10-3 farads. In addition, designations can be in nanofarads (nF) equal to 10-9 F and picofarads (pF) equal to 10-12 F. Capacitance markings for large capacitors are applied directly to the housing. In some designs, the markings may differ, but in general, you need to be guided by the units of measurement mentioned above.

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Designations are sometimes written in capital letters, for example, MF, which actually corresponds to mF - microfarads. The marking fd is also found - an abbreviated English word farad. Therefore mmfd will correspond to mmf or picofarad. In addition, there are designations that include a number and one letter. This marking looks like 400m and is used for small capacitors. In some cases, it is possible to apply tolerances, which are an acceptable deviation from the rated capacitance of the capacitor. This information is of great importance when, when assembling individual types electrical circuits capacitors with precise capacitance values ​​may be required. If we take the marking 6000uF + 50%/-70% as an example, then the maximum capacitance value will be 6000 + (6000 x 0.5) = 9000 uF, and the minimum 1800 uF = 6000 - (6000 x 0.7).

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If there are no percentages, you need to find the letter. Usually it is located separately or after the numeric designation of the container. Each letter corresponds to a specific tolerance value. After this, you can begin to determine the rated voltage. With large capacitor housing sizes, voltage markings are indicated by numbers followed by letters or letter combinations in the form V, VDC, WV or VDCW. The WV symbols correspond to the English phrase WorkingVoltage, which means operating voltage. Digital readings are considered to be the maximum permissible capacitor voltage, measured in volts.

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If there is no voltage marking on the device body, such a capacitor should only be used in low-voltage circuits. In an AC circuit, use a device designed specifically for this purpose. Capacitors designed for D.C., without the possibility of converting the rated voltage. The next step is to identify the positive and negative symbols that indicate the presence of polarity. Identifying plus and minus is important because incorrect identification of the poles can lead to short circuit and even a capacitor explosion. In the absence of special symbols, the device can be connected to any terminals, regardless of polarity.

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The pole designation is sometimes applied in the form of a colored stripe or a ring-shaped indentation. This marking corresponds to the negative contact in electrolytic aluminum capacitors, which are shaped like a tin can. In very small tantalum capacitors, these same symbols indicate positive contact. If there are plus and minus symbols, the color coding can be ignored. Other markings. The markings on the capacitor body allow you to determine the voltage value. The figure shows special symbols corresponding to the maximum permissible voltage for specific device. In this case, parameters are given for capacitors that can only be operated at constant current.

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Application of capacitors. The energy of a capacitor is usually not very high - no more than hundreds of joules. In addition, it is not preserved due to the inevitable charge leakage. Therefore, charged capacitors cannot replace, for example, batteries as sources of electrical energy. Capacitors can store energy for a more or less long time, and when charged through a low-resistance circuit, they release energy almost instantly. This property is widely used in practice. A flash lamp used in photography is powered by the electric current of a capacitor discharge, which is pre-charged by a special battery. Excitation of quantum light sources - lasers is carried out using a gas-discharge tube, the flash of which occurs when a bank of capacitors of large electrical capacity is discharged. However, capacitors are mainly used in radio engineering...

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Municipal autonomous educational institution

"Lyceum No. 7" Berdsk

Capacitors

8th grade

Physics teacher

I.V.Toropchina

Capacitor

Capacitor- This is a device designed to accumulate electrical charge and electric field energy.

Capacitor

Capacitor represents two

conductor (plate), separated by a layer

dielectric, the thickness of which is small

compared to the size of the conductors.

The entire electric field is concentrated inside the capacitor and is uniform.

Capacitor charge is the absolute value of the charge on one of the capacitor plates.

- by type of dielectric : air,

mica, ceramic,

electrolytic. - according to the shape of the linings : flat,

spherical, cylindrical. - by capacity size:

constants, variables.

• Depending on their purpose, capacitors have different designs.

• A conventional technical paper capacitor consists of two strips of aluminum foil, insulated from each other and from the metal casing by paper strips impregnated with paraffin. Strips and ribbons are tightly rolled into a small bag

Variable capacitors

Capacitor designation

Fixed capacitor

Variable capacitor

Electrical capacity

A physical quantity characterizing the ability of two conductors to accumulate an electric charge is called electrical capacity, or capacitance.

When the charge increases by 2, 3, 4 times, respectively, by 2, 3, 4

the readings of the electrometer will increase times, i.e. it will increase

voltage between the capacitor plates.

The charge to voltage ratio will remain

permanent:

Capacitance of the capacitor

• The quantity measured by the charge ratio ( q) one of the capacitor plates to voltage ( U) between the plates is called electrical capacity of the capacitor .
• The electrical capacity of the capacitor is calculated by the formula:

C=q/U

Units of electrical capacity

Electrical capacity is measured in farads (F)

[ WITH ] = 1F (farad)

The electrical capacity of two conductors is numerically

is equal to one if, when imparting charges to them

+1 C and -1 C there is a difference between them

potentials 1V

1F = 1Kl/V

Units of electrical capacity

1 µF (microfarad) = 10 -6 F

1 nF (nanofarad)=10 -9 F

1 pF (picofarad) = 10 -12 F

• The larger the area of ​​the plates, the greater the capacitance of the capacitor.
• As the distance between the plates of the capacitor decreases and the charge remains constant, the capacitance of the capacitor increases.
• When a dielectric is added, the capacitance of the capacitor increases.

The capacitance of the capacitor depends on the area of ​​the plates, the distance between the plates, and the properties of the added dielectric.

Electrical capacity

from geometric

conductor sizes

Depends

on the shape of the conductors and

their relative position

on electrical properties

environment between conductors

Capacitor energy

• In order to charge a capacitor, work must be done to separate positive and negative charges. In accordance with the law of conservation of energy, the work done A is equal to the energy of the capacitor E, i.e.

A = E,

where E is the energy of the capacitor.

• The work of the electric field of a capacitor can be found using the formula: A = qU cp ,

where U Wed is the average voltage value.

U Wed = U/2; then A = qU Wed = qU/2, since q = CU, then A = CU 2 /2.

• The energy of a capacitor with capacitance C is equal to:

W=CU 2 /2

• Capacitors can store energy for a long time, and when discharged, they release it almost instantly.
• The property of a capacitor to accumulate and quickly release electrical energy is widely used in electrical engineering and electronic devices, in medical technology (X-ray equipment, electrotherapy devices), in the manufacture of dosimeters, aerial photography.

• Flash lamp is powered by the electric current of the capacitor discharge.
• Gas discharge tubes light up when the capacitor bank is discharged.
• Radio engineering .

First capacitor was invented in 1745 by a German lawyer and scientist Ewald Jurgen von Kleistom

First capacitor: one cover is mercury, the other cover is the experimenter’s hand holding the jar.

• Almost the same experiment and almost at the same time was carried out in the Dutch city of Leiden by university professor Pieter van Musschenbroek.
• Having charged the water and taking the jar in one hand, he touched the metal rod with the other hand, which served to supply the charge to the water. At the same time, Muschenbroek felt such a strong blow to his arms, shoulders and chest that he lost consciousness, and took two days to come to his senses.
• Van Musschenbroeck's experiment became very famous, so the capacitor became known as the "Leyden jar".

Homework

§ 54, Exercise 38