Presentation on conductors in an electric field. There are free electrons

• What is an electric field?
• Name the main properties electrostatic field.
• What generates an electric field?
• What is tension electric field?
• What electric field is called uniform?
• How can a uniform electric field be obtained?
• How are the lines of force of a uniform electric field directed?
• How to calculate the strength of the electric field created by a point charge?

Conductors and dielectrics in an electrostatic field

Lecture plan:

• 1. Conductors and dielectrics.
• 2. Conductors in an electrostatic field.
• 3. Dielectrics in an electrostatic field.

Two types of dielectrics.

• 4. Dielectric constant.

The structure of metals

The last electron is weakly attracted to the nucleus because:

• far from the core
• 10 electrons repel the eleventh

the last electron is detached from the nucleus and becomes free

substances by conductivity

conductors

• conductors

dielectrics

are substances that do not conduct electricity

no free charges

are substances that conduct electricity

there are free charges

The structure of metals

The structure of metals

E internal

E ext.= E internal

Metal conductor in an electrostatic field

E ext.= E internal

E common =0

CONCLUSION:

There is no electric field inside the conductor.

The entire static charge of a conductor is concentrated on its surface.

The structure of the dielectric

structure of the salt molecule

electric dipole -

a set of two point charges that are equal in absolute value and opposite in sign.

The structure of a polar dielectric

Dielectric in an electric field

E internal E external .

E ext.

E internal

CONCLUSION:

DIELECTRIC WEAKEN THE EXTERNAL ELECTRIC FIELD

Galimurza S.A.

Dielectric constant of the medium

Electric field strength in vacuum

Electric field strength in a dielectric

Dielectric constant of the medium

E about

To the directory:

• Coulomb's law:
• The strength of the electric field created by a point charge:

q 1 q 2

r

2

q

r

2

What are microwaves?

Household microwave ovens use electromagnetic waves, the frequency of which is 2450 MHz - microwaves.

In such microwaves, the electric field 2 · 2 450 000 000 changes direction every second.

Microwave: microwave frequency 2450 MHz

How do microwaves heat food?

Heating of products occurs due to two physical mechanisms:

1. microwave heating of the surface layer

2. subsequent penetration of heat into the depth of the product due to thermal conductivity.

device

power,

frequency,

microwave

mobile phone

GSM class 4

mobile phone

Conductors in an electric field Free charges - charged particles of the same sign that can move under the influence of an electric field Bound charges - opposite charges that make up atoms (or molecules) that cannot move independently of each other under the influence of an electric field substances conductors dielectrics semiconductors

Any medium weakens the electric field strength

The electrical characteristics of a medium are determined by the mobility of charged particles in it

Conductor metal, solutions of salts, acids, humid air, plasma, human body

This is a body, inside which contains a sufficient amount of free electric charges that can move under the influence of an electric field.

If an uncharged conductor is introduced into an electric field, then charge carriers begin to move. They are distributed so that the electric field created by them is opposite to the external field, that is, the field inside the conductor will be weakened. The charges will be redistributed until the conditions for the equilibrium of charges on the conductor are met, that is:

a neutral conductor introduced into an electric field breaks the lines of tension. They end on negative induced charges and start on positive ones.

The phenomenon of spatial separation of charges is called electrostatic induction. The self-field of induced charges with a high degree of accuracy compensates for the external field inside the conductor.

If the conductor has an internal cavity, then the field will be absent inside the cavity. This circumstance is used when organizing the protection of equipment from electric fields.

The electrization of a conductor in an external electrostatic field by separating the positive and negative charges already present in it in equal amounts is called the phenomenon of electrostatic induction, and the redistributed charges themselves are called induced. This phenomenon can be used to electrify uncharged conductors.

An uncharged conductor can be electrified by contact with another charged conductor.

The distribution of charges on the surface of conductors depends on their shape. The maximum charge density is observed on the points, while inside the depressions it is reduced to a minimum.

The property of electric charges to concentrate in the near-surface layer of the conductor has been used to obtain significant potential differences by the electrostatic method. On fig. a diagram of an electrostatic generator used to accelerate elementary particles is given.

A spherical conductor 1 of large diameter is located on an insulating column 2. A closed dielectric tape 3 moves inside the column, driven by drums 4. From a high-voltage generator, an eclectic charge is transferred to a tape through a system of pointed conductors 5, on the back of the tape is located grounding plate 6. The charges from the tape are removed by a system of points 7 and flow down onto the conducting sphere. The value of the maximum charge that can accumulate on the sphere is determined by the leakage from the surface of the spherical conductor. In practice, generators of a similar design with a sphere diameter of 10–15 m can be used to obtain a potential difference of the order of 3–5 million volts. To increase the charge of the sphere, the entire structure is sometimes placed in a box filled with compressed gas, which reduces the ionization intensity.

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slide presentation

Slide text: Conductors and dielectrics in an electrostatic field Mezhetsky Artyom 10 "B" Completed by: Municipal educational institution"Secondary school No. 30 of the city of Belovo" Head: Popova Irina Alexandrovna Belovo 2011

Slide text: Plan: 1. Conductors and dielectrics. 2. Conductors in an electrostatic field. 3. Dielectrics in an electrostatic field. Two types of dielectrics. 4. Dielectric constant.

Slide text: conductive substances conductors are substances that conduct electric current there are free charges dielectrics are substances that do not conduct electric current there are no free charges

Slide text: The structure of metals + + + + + + + + + - - - - - - - - -

Slide text: Metal conductor in an electrostatic field + + + + + + + + + - - - - - - - - + + + + + Evt. Evt. Evt.= Etn. -

Slide text: Metal conductor in an electrostatic field E ext.= E int. Etot=0 CONCLUSION: There is no electric field inside the conductor. The entire static charge of a conductor is concentrated on its surface.

Slide text: The structure of the dielectric The structure of the sodium chloride NaCl molecule is an electric dipole - a set of two point charges that are equal in magnitude and opposite in sign. NaCl - - - - - - - - + - + -

Slide text: Types of dielectrics Polar Consist of molecules that do not have the same centers of distribution of positive and negative charges salt, alcohols, water, etc. Non-polar Consist of molecules in which the centers of distribution of positive and negative charges coincide. inert gases, O2, H2, benzene, polyethylene, etc.

Slide text: The structure of a polar dielectric + - + - + - + - + - + -

Slide #10

Slide text: Dielectric in an electric field + - + + + + + + + - E ext. E int. + - + - + - + - E int.< Е внеш. ВЫВОД: ДИЭЛЕКТРИК ОСЛАБЛЯЕТ ВНЕШНЕЕ ЭЛЕКТРИЧЕСКОЕ ПОЛЕ

Slide #11

Slide text: Dielectric constant environments - characteristic electrical properties of the dielectric E Eo - electric field strength in vacuum - electric field strength in the dielectric - permittivity of the medium = Eo E

Slide #12

Slide text: Dielectric constant of substances substance Dielectric constant of medium water 81 kerosene 2.1 oil 2.5 paraffin 2.1 mica 6 glass 7

Slide #13

Slide text: Coulomb's Law: The strength of the electric field created by a point charge: q1 q2 r 2 q r 2

Slide #14

Slide text: Task

Slide #15

Slide text: Problem solving

Slide #16

Slide text: Problem solving

Slide #17

Slide text: Problem solving

Slide #18

Slide text: Test No. 1: A positively charged body is brought to three contacting plates A, B, C. Plates B, C are a conductor, and A is a dielectric. What charges will be on the plates after plate B has been completely pulled out? Answer options

Slide #19

Slide text: No. 2: A charged metal ball is successively immersed in two dielectric liquids (1< 2). Какой из нижеприведенных графиков наиболее точно отражает зависимость потенциала поля от расстояния, отсчитываемого от центра шара?

Slide #20

Slide text: No. 3: When the space between the plates of a flat capacitor was completely filled with a dielectric, the field strength inside the capacitor changed 9 times. How many times has the capacitance of the capacitor changed? A) It has tripled. B) Decreased by 3 times. C) Increased 9 times. D) Decreased by 9 times. E) Hasn't changed.

Slide #21

Slide text: #4: A positive charge was placed in the center of a thick-walled, uncharged metal sphere. Which of the following figures corresponds to the distribution pattern of the lines of force of the electrostatic field?

Slide #22

Slide text: No. 5: Which of the following figures corresponds to the distribution pattern of field lines for a positive charge and a grounded metal plane?

Slide #23

Slide text: Literature used Kasyanov, V.A. Physics, grade 10 [Text]: textbook for general education schools/ V.A. Kasyanov. - LLC "Drofa", 2004. - 116 p. Kabardin O.F., Orlov V.A., Evenchik E.E., Shamash S.Ya., Pinsky A.A., Kabardina S.I., Dick Yu.I., Nikiforov G.G., Shefer N .AND. "Physics. Grade 10”, “Enlightenment”, 2007

Slide #24

Slide text: Everything =)

Conductors and dielectrics

Slides: 8 Words: 168 Sounds: 0 Effects: 0

Electric field in matter. Any medium weakens the strength of the electric field. The electrical characteristics of a medium are determined by the mobility of charged particles in it. Substances, conductors, semiconductors, dielectrics. Substances. Free charges are charged particles of the same sign that can move under the influence of an electric field. Bound charges are unlike charges that cannot move under the action of an electric field independently of each other. Conductors. Conductors are substances in which free charges can move throughout the volume. Conductors - metals, solutions of salts, acids, moist air, plasma, human body. - Explorer.ppt

Conductors in an electric field

Slides: 10 Words: 282 Sounds: 1 Effects: 208

conductors in an electric field. There is no electric field in other conductors. Let's consider an electric field inside a metal conductor…… Dielectrics. In nonpolar dielectrics, the center of positive and negative charge is the same. In an electric field, any dielectric becomes polar. Dipole. Polarization of dielectrics. - Conductors in an electric field.ppt

Conductors in an electrostatic field

Slides: 11 Words: 347 Sounds: 0 Effects: 18

Conductors and dielectrics in an electrostatic field. Conductors in an electrostatic field Dielectrics in an electrostatic field. - Metals; liquid solutions and melts of electrolytes; plasma. Conductors include: Conductors in an electrostatic field. Evnesh. The inner field will weaken the outer one. Evt. There is no field inside a conductor placed in an electrostatic field. Electrostatic properties of homogeneous metallic conductors. Dielectrics. Polar. Nonpolar. Dielectrics include air, glass, ebonite, mica, porcelain, dry wood. Dielectrics in an electrostatic field. - Conductors in an electrostatic field.ppt

Conductors and dielectrics

Slides: 18 Words: 507 Sounds: 0 Effects: 206

Electric field. Conductors and dielectrics in an electrostatic field. Conductors and dielectrics. Conductive substances. last electron. The structure of metals. Metal conductor. Metal conductor in an electrostatic field. The structure of the dielectric. The structure of a polar dielectric. Dielectric in an electric field. Dielectric permittivity of the medium. Coulomb's law. Microwave. Microwave. How microwaves heat food. Power. - Conductors and dielectrics.ppt

Conductors in an electric field Dielectrics in an electric field

Slides: 18 Words: 624 Sounds: 1 Effects: 145

Topic: "Conductors and dielectrics in an electric field." Conductors. charge inside a conductor. According to the principle of superposition of fields, the tension inside the conductor is zero. conductive sphere. Take an arbitrary point A. The charges of the sites are equal. electrostatic induction. equipotential surfaces. The most famous electric fish are. Electric Stingray. Electric eel. Dielectrics. Dielectrics are materials in which there are no free electric charges. There are three types of dielectrics: polar, non-polar and ferroelectric. - Conductors in an electric field Dielectrics in an electric field.ppt

Electric field in dielectrics

Slides: 31 Words: 2090 Sounds: 0 Effects: 0

Dielectrics do not conduct electricity under normal conditions. The term "dielectrics" was introduced by Faraday. A dielectric, like any substance, consists of atoms and molecules. Dielectric molecules are electrically neutral. Polarization. Field strength in a dielectric. Under the action of the field, the dielectric is polarized. The resulting field inside the dielectric. Field. electrical displacement. The external field is created by a system of free electric charges. Gauss's theorem for a field in a dielectric. Gauss's theorem for an electrostatic field in a dielectric. The properties of ferroelectrics strongly depend on temperature. - Dielectric.ppt

Polarization of dielectrics

Slides: 20 Words: 1598 Sounds: 0 Effects: 0

Polarization of dielectrics. Relative permittivity. Polarization vector. Mechanisms of polarization. spontaneous polarization. migratory polarization. Types of elastic polarization. Ionic elastic polarization. Dipole elastic polarization. Types of thermal polarization. Dipole thermal polarization. Electronic thermal polarization. The dielectric constant. Ferroelectrics. Piezoelectrics. Piezoelectric effects are observed only in crystals that do not have a center of symmetry. Pyroelectrics. Pyroelectrics exhibit spontaneous polarization along the polar axis. Photopolarization. -

CONDUCTORS AND DIELECTRIC IN ELECTRIC FIELD

Basic course

• Conductors are substances that contain free electric charges capable of moving under the influence of an arbitrarily weak electric field.

CONDUCTORS

IONIZED

GASES

METALS

ELECTROLYTES

Electrostatic protection- a phenomenon according to which it is possible to shield the electric field by "hiding" from it inside a closed shell of an electrically conductive material (for example, metal).

Electrostatic protection.

The phenomenon was discovered by Michael Faraday in 1836. He noticed that an external electric field cannot get inside a grounded metal cage. Principle of operation Faraday cages is that under the action of an external electric field, free electrons in the metal begin to move and create a charge on the surface of the cell, which completely compensates for this external field.

Dielectrics (or insulators) are substances that conduct electricity relatively poorly (compared to conductors).

• In dielectrics, all electrons are bound, that is, they belong to individual atoms, and the electric field does not tear them off, but only slightly displaces them, that is, polarizes them. Therefore, an electric field can exist inside the dielectric, the dielectric has a certain effect on the electric field

Dielectrics are divided into polar and non-polar .

Polar dielectrics

consist of molecules in which the centers of distribution of positive and negative charges do not coincide. Such molecules can be represented as two identical in modulus opposite point charges located at some distance from each other, called dipole .

Non-polar dielectrics

consist of atoms and molecules in which the centers of distribution of positive and negative charges coincide.

Polarization of polar dielectrics.

• The placement of a polar dielectric in an electrostatic field (for example, between two charged plates) leads to a turn and displacement of previously randomly oriented dipoles along the field.

The reversal occurs under the action of a pair of forces applied from the side of the field to two charges of the dipole.

The displacement of dipoles is called polarization. However, only partial polarization occurs due to thermal motion. Inside the dielectric, the positive and negative charges of the dipoles compensate each other, and a bound charge appears on the surface of the dielectric: negative on the side of the positively charged plate, and vice versa.

Polarization of non-polar dielectrics

A nonpolar dielectric in an electric field also polarizes. Under the influence of an electric field, positive and negative charges in a molecule are shifted in opposite directions, so that the centers of charge distribution are shifted, as in polar molecules. The axis of the dipole induced by the field is oriented along the field. Bound charges appear on the dielectric surfaces adjacent to the charged plates.

A polarized dielectric itself creates an electric field.

This field weakens the external electric field inside the dielectric

The degree of this attenuation depends on the properties of the dielectric.

The decrease in the strength of the electrostatic field in matter compared to the field in vacuum is characterized by the relative permittivity of the medium.

Conductors in an electric field

Dielectrics in an electric field

1. There are free electrons

1. There are no free charge carriers.

2.electrons are collected on the surface of the conductor

2. In an electric field, molecules and atoms rotate so that on the one hand, an excess positive charge appears in the dielectric, and on the other, a negative charge

3. There is no electric field inside the conductor

3. The electric field inside the conductor weakens by ε times.

4. The conductor can be divided into 2 parts in an electric field, and each part will be charged with different signs.

4. Dielectric can be divided into 2 parts in an electric field, but each of them will be uncharged

test questions

1 . What substances are called conductors?

2 What electric charges are called free?

3. What particles are carriers of free charges in metals?

4. What happens in a metal placed in an electric field?

5. How is the dawn communicated to him distributed over the conductor d?

TEST QUESTIONS.

6. If a conductor in an electric field is divided into two parts, how will these parts be charged?

7. On what principle is electrostatic protection based?

8. What substances are called dielectrics?

9. What are dielectrics? What is the difference?

10. Explain the behavior of a dipole in an external electric field.

11. How dielectric polarization occurs.

12. If a dielectric placed in an electric field is divided in half, what will be the charge of each part?

13. A negatively charged cloud passes over the lightning rod. Explain on the basis of electronic concepts why a charge arises on the tip of a lightning rod. What is his sign?