Presentation for 8th grade on the physics of capacitors. Presentation on the topic capacitor. Variable capacitors

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 can retain 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.

Slide 1

Types of capacitors and their applications.

Slide 2

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

Slide 3

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.

Slide 4

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.

Slide 5

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.

Slide 6

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.

Slide 7

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.

Slide 8

Variable capacitors.

Variable capacitors are widely used in devices that often require adjustments 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.

Slide 9

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.

Slide 10

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.

Slide 11

Due to the ability of capacitors to accumulate charge for a long time and then quickly discharge in a circuit with low resistance to create a pulse, it makes 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.

Slide 12

The ability of a capacitor to accumulate and store electrical charge for a long time has made it possible to use it in elements for storing 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.

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Slide 7

“Capacitor physics” - Types of capacitors. - Paper capacitor - mica capacitor electrolytic capacitor. Air condenser. Capacitor connections. - Air condenser. Definition of a capacitor. When connecting an electrolytic capacitor, polarity must be observed. Purpose of capacitors.

“Using capacitors” - Experiments with a capacitor. The capacitor is used in ignition circuits. Energy formulas. Application of capacitors. Features of the use of capacitors. The capacitor is used in medicine. Lamps with discharge lamps. Capacitive keyboard. Capacitor. Cell phones. Used in telephony and telegraphy.

“Electrical capacity and capacitors” - In the computer keyboard. Variable capacitor. Connection of capacitors. Electrical capacity. Consistent. Flashlights. Capacitor connection diagrams. Designation on electrical diagrams: Capacitors. Electrical capacity of a flat capacitor. The entire electric field is concentrated inside the capacitor.

“Use of capacitors” - For the latter batteries, regeneration time is fundamentally important. Polymer capacitors with solid electrolyte on the chipset. Diagram of a telephone bug. Current rectifier circuit. Capacitor CTEALTG STC - 1001. Condenser microphone. A successful association is on the Sciencentral website. Studio condenser directional microphone for wide applications.

“Capacitor” - Capacity of the capacitor. Charge ratio. Capacitor energy. Variable capacitor. Paper capacitor. Square. Capacitor. Application of capacitors. Physics lesson in 9th grade

“Capacitors. Electrical capacity »

Purpose: To form an idea of ​​​​a capacitor, about the electrical capacity of a capacitor, to introduce a unit of measurement of electrical capacity, to consider the dependence of the capacitance of a capacitor on its geometric design.

1 . Coulomb's law: 2. The force characteristic of the field is... 3. The intensity can be found using the formula: 4. Field intensity of a point charge: 5. Field intensity of a plane: 6. The direction of the intensity is taken... 7. The energy characteristic of the field is... 8. Give the characteristic Let's repeat...

A capacitor consists of two conductors separated by a dielectric layer, the thickness of which is small compared to the size of the conductors. Capacitor

Designation of a capacitor in an electrical diagram. - + + + + + - - - - E - q + q

If two conductors isolated from each other are given charges q 1 and q 2, then a certain potential difference Δφ arises between them, depending on the magnitude of the charges and the geometry of the conductors. The potential difference Δφ between two points in an electric field is often called voltage and is symbolized by the letter U. Of greatest practical interest is the case when the charges of the conductors are identical in magnitude and opposite in sign: q 1 = – q 2 = q. In this case, we can introduce the concept of electrical capacitance.

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.

According to the principle of superposition, the field strength created by both plates is equal to the sum of the strengths and fields of each of the plates:

Outside the plates, the vectors and are directed in different directions, and therefore E = 0. The surface charge density σ of the plates is equal to q / S, where q is the charge and S is the area of ​​each plate. The potential difference Δφ between the plates in a uniform electric field is equal to Ed, where d is the distance between the plates. From these relationships we can obtain a formula for the electrical capacity of a flat capacitor, where ε o =8.85·10 -12 F/m is the electrical constant.

Thus, the electrical capacity of a flat capacitor is directly proportional to the area of ​​the plates (plates) and inversely proportional to the distance between them. If the space between the plates is filled with a dielectric, the electrical capacity of the capacitor increases by ε times:

Capacitors can be connected to each other to form capacitor banks. When connecting capacitors in parallel (Figure No. 3), the voltages on the capacitors are the same: U 1 = U 2 = U, and the charges are equal to q 1 = C 1 U and q 2 = C 2 U. Such a system can be considered as a single capacitor of electrical capacity C, charged with a charge q = q 1 + q 2 at a voltage between the plates equal to U. this implies

Thus, when connected in parallel, the electrical capacitances add up. Parallel connection of capacitors. C = C 1 + C 2. Series connection of capacitors. .

When connected in series (Figure 4), the charges of both capacitors are the same: q 1 = q 2 = q, and the voltages across them are equal and Such a system can be considered as a single capacitor charged with charge q at a voltage between the plates U = U 1 + U 2. Hence,

Types of capacitors

Application of capacitors Types of capacitors: - air, - paper, - mica, - electrostatic. Purpose: To accumulate charge or energy for a short time to quickly change the potential. Do not pass direct current. In radio engineering - an oscillatory circuit, a rectifier. Application in photographic equipment.

Variable capacitors with air or solid dielectric Variable capacitors with air or solid dielectric are often used. They consist of two systems of metal plates insulated from each other. One system of plates is stationary, the second can rotate around an axis. By rotating the moving system, the capacitance of the capacitor is smoothly changed.

Pinned3Zie. What are capacitors used for? How does a capacitor work? Why is the space between the capacitor plates filled with dielectrics? What is the electrical capacity of a charged capacitor? What does electrical capacity depend on? Consolidation.

The distance between the plates of a square flat capacitor with a side of 20 cm is 1 mm. What is the potential difference between the plates if the charge of the capacitor is 2 nC. task

: Solution:

Lesson summary: What new or interesting things did you learn in class today? What did you study?

Homework: § 99, 100 Ex. 18