Application of capacitors presentation. Capacitors - their role and functions

Signs of pregnancy after embryo implantation

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 ability of a capacitor to accumulate and quickly release electrical energy is widely used in electrical and electronic devices, medical equipment (X-ray equipment, electrotherapy devices), in the manufacture of dosimeters, and 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 taken 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

"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. Electric current... 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

9th grade 5klass.net

Slide 2

The purpose of the lesson:

Form the concept of electrical capacity; Introduce a new characteristic - the electrical capacity of the capacitor, and its unit of measurement. Consider the types of capacitors and where they are used

Slide 3

Let's repeat... Option 1 1) Who and when was the theory of the electromagnetic field created and what is its essence. 2) List the types of electromagnetic waves. Infrared radiation, its properties and effect on the human body. Option 2 1) What is called an electromagnetic wave? What are the main properties of an electromagnetic wave? 2) List the types of electromagnetic waves. X-ray radiation, its properties and effect on the human body.

Slide 4

A capacitor consists of two conductors separated by a dielectric layer, the thickness of which is small compared to the size of the conductors. The electrical capacity of the capacitor is equal to where q is the charge of the positive plate, U is the voltage between the plates. The electrical capacity of a capacitor depends on its geometric design and the electrical permittivity of the dielectric filling it and does not depend on the charge of the plates. Capacitor

Slide 5

The electrical capacitance of two conductors is the ratio of the charge of one of the conductors to the potential difference between this conductor and the neighboring one. The unit of measurement of capacitance is farad – [F] You need to know this:

Slide 6

The electrical capacity of a flat capacitor is equal to where S is the area of ​​each of the plates, d is the distance between them, ε is the dielectric constant of the substance between the plates. It is assumed that the geometric dimensions of the plates are large compared to the distance between them. Remember that...

Slide 7

Capacitor energy

W = qU/2 W=q2 /2C U

Slide 8

Types of capacitors

Slide 9

Currently, paper capacitors are widely used for voltages of several hundred volts and a capacity of several microfarads. In such capacitors, the plates are two long strips of thin metal foil, and the insulating spacer between them is a slightly wider paper strip impregnated with paraffin. One of the covers is covered with paper tape, then the tapes are tightly rolled into a roll and placed in a special case. Such a capacitor, having the size of a matchbox, has a capacity of 10 μF (a metal ball of such capacity would have a radius of 90 km). Paper capacitor

Slide 10

Ceramic capacitor Ceramic capacitors are used in radio engineering. The dielectric in them is special ceramics. The linings of ceramic capacitors are made in the form of a layer of silver applied to the surface of the ceramic and protected with a layer of varnish. Ceramic capacitors are manufactured with capacities ranging from units to hundreds of picofarads and voltages from hundreds to thousands of volts.

Slide 11

Variable capacitor.

Write down the device of the capacitor

Slide 12

Write down what their electrical capacity is.

Slide 13

APPLICATION 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...


    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 the 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

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