Capacitors, device purpose and types of presentation. Types of capacitors









General purpose capacitors are 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.

"Alternating Current" - Definition. Alternating current is an electric current that changes over time in magnitude and direction. Alternating current. Alternator. EZ 25.1 Producing alternating current by rotating a coil in a magnetic field.

“The action of electric current” - You need to make an accurate cast of some wooden relief. How can we judge the amount of electricity passed by the chemical effect of current? What effects of electric current occur in your apartment? "Let's think about it." Select equipment for the experiment on the demonstration table in accordance with the picture.

“Electric current power” - A. A=IU B. P=UI C. I=U/R A. A=UI B. P=UI B. A=UIt A. W B. A C. B A. 100 W B. 400 W B. 4 kW. The effect of current is characterized by two quantities. Voltage... Current work A=UIt. Electricity... Current strength... The power of an electric iron is 600 W, and the power of a TV is 100 W. Know the definition of the work and power of electric current in a section of a circuit?

“Electrical capacity and capacitors” - Parallel. Capacitors. Variable capacitor. The entire electric field is concentrated inside the capacitor. -q. Energy of a charged capacitor. Connection of capacitors. Electrical capacity. Consistent. Designation on electrical diagrams: Constant capacitor. +q. Derivation of the formula for the energy of a charged capacitor.

"Alternating electric current" - The result is the average power over a period. Alternating Electric Current. The instantaneous current value is directly proportional to the instantaneous voltage value. E=-ф’= -bs(cos ?t)’= = bs? * sin ?t = em sin ?t. Conversely, undamped forced oscillations are of great practical importance. U=Um cos?t.

"Capacitor physics" - - Paper capacitor - mica capacitor electrolytic capacitor. Purpose of capacitors. Capacitors. When connecting an electrolytic capacitor, polarity must be observed. Air condenser. Definition of a capacitor. Presentation in Physics on the Topic: Paper capacitor. The work was completed by: Regina Dautova.

There are 9 presentations in total


Pieter van Muschenbrouck ()





What is a capacitor? Capacitor (from Latin condense “to compact”, “to thicken”) is a two-terminal network with a certain capacitance value and low ohmic conductivity; device for storing electric field energy. A capacitor is a passive electronic component. Typically consists of two plate-shaped electrodes (called plates) separated by a dielectric whose thickness is small compared to the dimensions of the plates.


Properties of a capacitor A capacitor in a DC circuit can conduct current at the moment it is connected to the circuit (the capacitor is charged or recharged); at the end of the transient process, no current flows through the capacitor, since its plates are separated by a dielectric. In an alternating current circuit, it conducts alternating current oscillations through cyclic recharging of the capacitor, closing with the so-called bias current of the direct current circuit with a bias current


In terms of the complex amplitude method, a capacitor has a complex impedance:complex amplitude impedance method The resonant frequency of a capacitor is equal to: Resonant frequency When a capacitor in an alternating current circuit behaves like an inductor. Therefore, it is advisable to use a capacitor only at frequencies at which its resistance is capacitive in nature. Typically, the maximum operating frequency of a capacitor is about 23 times lower than the resonant inductor




Main parameters. Capacitance The main characteristic of a capacitor is its capacitance, which characterizes the capacitor’s ability to accumulate electrical charge. The designation of a capacitor indicates the value of the nominal capacitance, while the actual capacitance can vary significantly depending on many factors. The actual capacitance of a capacitor determines its electrical properties. So, according to the definition of capacitance, the charge on the plate is proportional to the voltage between the plates (q = CU). Typical capacitance values ​​range from a few picofarads to hundreds of microfarads. However, there are capacitors with a capacity of up to tens of farads. capacitanceelectric chargecharge voltagefarad The capacitance of a flat capacitor consisting of two parallel metal plates of area each, located at a distance d from each other, in the SI system is expressed by the SI formula


To obtain large capacities, capacitors are connected in parallel. In this case, the voltage between the plates of all capacitors is the same. The total capacity of a battery of parallel-connected capacitors is equal to the sum of the capacitances of all capacitors included in the battery. If all parallel-connected capacitors have the same distance between the plates and the same dielectric properties, then these capacitors can be represented as one large capacitor, divided into fragments of a smaller area. When capacitors are connected in series, the charges of all capacitors are the same, since they are supplied from the power source only to the external electrodes, and on the internal electrodes they are obtained only due to the separation of charges that previously neutralized each other. The total capacity of a battery of series-connected capacitors is equal to


Specific capacity. Capacitors are also characterized by specific capacitance, the ratio of capacitance to the volume (or mass) of the dielectric. The maximum value of specific capacitance is achieved with a minimum thickness of the dielectric, but at the same time its breakdown voltage decreases.


Energy Density The energy density of an electrolytic capacitor depends on design. The maximum density is achieved with large capacitors, where the mass of the housing is small compared to the mass of the plates and electrolyte. For example, an EPCOS B4345 capacitor with a capacity of µF x 450 V and a mass of 1.9 kg has an energy density of 639 J/kg or 845 J/l. This parameter is especially important when using a capacitor as an energy storage device, followed by its instant release, for example, in a Gauss gun.


Rated voltage Another equally important characteristic of capacitors is the rated voltage - the voltage value indicated on the capacitor at which it can operate under specified conditions during its service life while maintaining parameters within acceptable limits. The rated voltage depends on the design of the capacitor and the properties of the materials used. During operation, the voltage on the capacitor should not exceed the rated voltage. For many types of capacitors, as the temperature increases, the permissible voltage decreases, which is associated with an increase in the thermal speed of charge carriers and, accordingly, a decrease in the requirements for the formation of electrical breakdown. temperature charge carrier speed


Polarity Many oxide dielectric (electrolytic) capacitors operate only when the voltage polarity is correct due to the chemical characteristics of the interaction of the electrolyte with the dielectric. When the voltage polarity is reversed, electrolytic capacitors usually fail due to chemical destruction of the dielectric with a subsequent increase in current, boiling of the electrolyte inside and, as a result, the possibility of explosion of the housing. electrolytic electrolyte explosion




IN modern technology Capacitors find extremely wide and versatile applications, especially in the fields of electronics. In radio engineering and television equipment In radar technology In telephony and telegraphy In automation and telemechanics In computer technology In electrical measuring technology In laser technology
















In modern power engineering, capacitors also find very diverse and important applications: 1. To improve power factor and industrial installations (cosine or shunt capacitors); 2.For longitudinal capacitance compensation of long-distance transmission lines and for voltage regulation in distribution networks (serial capacitors); 3. For capacitive energy extraction from high-voltage transmission lines and for connecting special communication equipment and protective equipment (communication capacitors) to transmission lines; 4.For surge protection.






2. In the mining industry (coal, metal ore, etc.) - in mining transport on capacitor electric locomotives of normal and high frequency (non-contact), in electric explosive devices using the electrohydraulic effect, etc.

MAOU Gymnasium No. 1

Presentation on physics in 10th grade

"Capacitors"

Physics teacher

I qualification category

Belogorsk, Amur Region

Elena Nikolaevna Klimenko Physics teacher Presentation on the topic “Lens” Grade 11 Municipal educational institution secondary school with in-depth study of individual subjects No. 1 Belogorsk, Amur Region


CAPACITOR – two conductors (plates) separated by a dielectric layer, the thickness of which is small compared to the size of the conductors.

WITH- electrical capacity (the ability of two conductors to accumulate electrical charge).

C=q/U q- charge, U- voltage

In SI, electrical capacity is measured in F (farad), 1F = 1 C/V


Capacitance of the capacitor depends from:

  • distance between plates –d(m),
  • plate area –S(m),
  • depending on the type of dielectric – ε (dielectric constant of the medium).

C =εέS/d

έ – electrical constant



Based on the type of dielectric, capacitors are divided into:

  • Vacuum
  • Gaseous
  • Liquid
  • Glass
  • Mica
  • Ceramic
  • Paper
  • Electrolytic
  • Oxide semiconductor

Methods for connecting capacitors:

  • sequential

2) parallel


Capacitors are distinguished by the possibility of changing their capacitance :

  • permanent capacitors - capacity does not change
  • variable capacitors - the capacity changes during the operation of the equipment
  • Trimmer capacitors – the capacity changes during one-time or periodic adjustment and does not change during operation of the equipment

Energy of a charged capacitor determined by the formula:

Si: [W] = J


Name

Capacity

Flat capacitor

Scheme

Cylindrical capacitor

Spherical capacitor

Application of capacitors :

  • Capacitors (together with inductors and/or resistors) are used to construct various circuits with frequency-dependent properties, in particular, filters, chains feedback , oscillatory circuits and so on.
  • When a capacitor is quickly discharged, a high power pulse can be obtained, for example, in photo flashes , electromagnetic accelerators , optically pumped pulsed lasers , Marx generators, (GIN; GIT) , generators Cockcroft-Walton and so on.
  • Since a capacitor is capable of retaining a charge for a long time, it can be used as an element memory or electrical energy storage devices.
  • Liquid level meter. A non-conducting liquid fills the space between the plates of the capacitor, and the capacitance of the capacitor varies depending on the level
  • Measuring transducer (MT) of air humidity, wood (a change in the composition of the dielectric leads to a change in capacitance).
  • Capacitors are able to accumulate a large charge and create high voltage on the plates, which is used for acceleration charged particles or to create short-term powerful electrical discharges

Literature sources:

1.Handbook of physics. H. Kuhling., Moscow “Mir”, 1983.

2. Textbook on physics 10th grade G.Ya.Myakishev. , B.B. Bukhovtsev., N.N. Sotsky. 2004.

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