Presentation on the topic of dielectrics in an electric field. Presentation on the topic "Conductors in an electric field"

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Slide text: Conductors and dielectrics in an electrostatic field Artem Mezhetsky 10 “B” Performed by: Municipal educational institution “Secondary school No. 30 of the city of Belovo” Head: Popova Irina Aleksandrovna 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: substances by conductivity 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: Structure of metals + + + + + + + + + - - - - - - - - -

Slide text: Metal conductor in an electrostatic field + + + + + + + + + - - - - - - - - + + + + + Ev. Evn. Evn. = Evn. -

Slide text: Metal conductor in an electrostatic field E external = E internal. Total=0 OUTPUT: There is no electric field inside the conductor. The entire static charge of a conductor is concentrated on its surface.

Slide text: Structure of a dielectric, structure of a molecule of table salt NaCl, electric dipole - a combination of two point charges, equal in magnitude and opposite in sign. Na Cl - - - - - - - - + - + -

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

Slide text: Structure of a polar dielectric + - + - + - + - + - + -

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

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

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

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Slide text: Coulomb's Law: Electric field strength created by a point charge: q1 q2 r 2 q r 2

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Slide text: Task

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Slide text: Solving the problem

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Slide text: Problem solving

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Slide text: Problem solving

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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 is completely pulled out? Answer options

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

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Slide text: No. 3: When the space between the plates of a flat capacitor is completely filled with a dielectric, the field strength inside the capacitor changes 9 times. How many times did the capacitance of the capacitor change? A) Increased by 3 times. B) Decreased by 3 times. C) Increased 9 times. D) Decreased by 9 times. E) Has not changed.

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Slide text: No. 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 electrostatic field lines?

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

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Slide text: References Kasyanov, V.A. Physics, 10th grade [Text]: textbook for secondary 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., Dik Yu.I., Nikiforov G.G., Shefer N. .AND. "Physics. 10th grade”, “Enlightenment”, 2007

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Slide text: Everything =)

CONDUCTORS AND DIELECTRICS IN AN ELECTRIC FIELD

Basic course

Conductors are substances that contain free electrical charges that can move 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 an electric field by “hiding” from it inside a closed shell made of electrically conductive material (for example, metal).

Electrostatic protection.

The phenomenon was discovered by Michael Faraday in 1836. He noticed that an external electric field could not get inside a grounded metal cage. Principle of operation Faraday cages lies in the fact that under the influence of an external electric field, free electrons located in the metal begin to move and create a charge on the surface of the cell that 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, i.e., they belong to individual atoms, and the electric field does not tear them off, but only slightly shifts them, i.e., polarizes them. Therefore, an electric field can exist inside the dielectric; the dielectric has a certain influence 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 molecules 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.

Placing a polar dielectric in an electrostatic field (for example, between two charged plates) leads to a reversal and displacement of previously chaotically oriented dipoles along the field.

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

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

Polarization of non-polar dielectrics

A non-polar dielectric in an electric field is also polarized. 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 displaced, like those of polar molecules. The axis of the field-induced dipole 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.

A decrease in the strength of the electrostatic field in a substance compared to the field in a vacuum is characterized by the relative dielectric constant 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 collect on the surface of the conductor

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

3. There is no electric field inside the conductor

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

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

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

Control questions

1 . What substances are called conductors?

2What 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 the dawn communicated to him is distributed over the conductor d?

CONTROL QUESTIONS.

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

7.What principle is electrostatic protection based on?

8.What substances are called dielectrics?

9.What types of dielectrics are there? What is the difference?

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

11. How polarization of dielectrics 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 a lightning rod. Explain, based on electronic concepts, why a charge appears at the tip of the lightning rod. What is his sign?

Conductors and dielectrics

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Electric field in matter. Any environment weakens the electric field strength. 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 influence 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

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

Conductors in an electrostatic field

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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 internal field will weaken the external one. Evn. There is no field inside a conductor placed in an electrostatic field. Electrostatic properties of homogeneous metal conductors. Dielectrics. Polar. Non-polar. Dielectrics include air, glass, ebonite, mica, porcelain, and dry wood. Dielectrics in an electrostatic field. - Conductors in an electrostatic field.ppt

Conductors and dielectrics

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Electric field. Conductors and dielectrics in an electrostatic field. Conductors and dielectrics. Substances by conductivity. Last electron. Structure of metals. Metal conductor. Metal conductor in an electrostatic field. Dielectric structure. The structure of a polar dielectric. Dielectric in an electric field. Dielectric constant 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

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Topic: “Conductors and dielectrics in an electric field.” Conductors. Charge inside a conductor. According to the principle of field superposition, the tension inside the conductor is zero. Conducting sphere. Let's take an arbitrary point A. The charges of the areas are equal. Electrostatic induction. Equipotential surfaces. The most famous electric fish are. Electric Stingray. Electric eel. Dielectrics. Dielectrics are materials that have no free electrical charges. There are three types of dielectrics: polar, non-polar and ferroelectrics. - Conductors in an electric field, dielectrics in an electric field.ppt

Electric field in dielectrics

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Dielectrics do not conduct electric current 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 influence of the field, the dielectric is polarized. The resulting field inside the dielectric. Field. Electrical bias. 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 the electrostatic field in a dielectric. The properties of ferroelectrics strongly depend on temperature. - Dielectric.ppt

Polarization of dielectrics

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Polarization of dielectrics. Relative dielectric constant. Polarization vector. Mechanisms of polarization. Spontaneous polarization. Migration 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. -

Slide 1

Conductors are substances in which there are many free charged particles. For example, in metals these are the electrons of the outer shell, which are connected with the nuclei of atoms very weakly and therefore actually belong to the metal conductor as a whole. This is the so-called electron gas. It is precisely due to the presence of charged particles that can move freely throughout the entire volume of a metal conductor that there is no electric field inside metals. There is no electric field in other conductors either. Consider the electric field inside a metal conductor......

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Because E0 = E1, then E = E0-E1= 0 There is no electric field inside the conductor

Slide 4

When charges are in equilibrium, there is no electric field inside the conductor, and the charges are located on its surface.

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Dielectrics

These are substances that have no free charged particles inside them. It is necessary to distinguish between polar dielectrics, in which the center of the positive and negative charge does not coincide. In non-polar dielectrics, the center of the positive and negative charge coincides. In an electric field, any dielectric becomes polar.

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Dipole

This is a system of two connected opposite charges, in which the center of the positive and negative charge does not coincide. A dipole placed in an electric field is subject to a torque, causing it to orient itself along the field. M=F٠L, where L is the distance between the centers of bound charges.