Equipment: multimedia projector, interactive whiteboard, lesson presentation
DURING THE CLASSES
I. Knowledge Test
1. Coulomb's law (frontal survey):
a) Name the scientist who experimentally established the law of interaction of point electric charges in vacuum. ( French scientist C. Coulomb in 1795).
b) What was the name of the device with which Coulomb's law was experimentally established? ( Torsional dynamometer, or as it was then called torsion balances).
c) Formulate Coulomb's law.
d) Write the formula of Coulomb's law.
e) With which law from the section "Mechanics" can an analogy be drawn for Coulomb's law? ( With the law of gravity:;).
f) Indicate the limits of applicability of the Coulomb law ( a) the charges must be stationary, b) point).
II. New topic
1. Electric field:
a) Referring to the completed home experimental tasks, the teacher brings students to the concept electric field (space around a charged body) and its discovery.
Students remember that you can detect an electric field using a magnetic needle made of paper (or foil).
The teacher immediately shows that the electric field can also be detected using an electrometer.
As a conclusion of previous observations, students are led to the statement that the electric field, like any kind of matter, is material and exists independently of our consciousness.(By analogy, we recall the gravitational field).
2. Characteristics of the electric field
a) tension.
(Students are reminded that any kind of matter can be characterized in some way. The same can be done with an electric field).
One of the characteristics of the electric field is the intensity:
It is specified that The electric field strength is the power characteristic of the electric field.
b) The intensity of a unit charge. (According to Coulomb's law):
; is the intensity of a single charge.
c) The principle of superposition (overlay) of fields:
3. Graphical representation of electric fields
lines of force fields - lines of tension.
Field lines of force start on a positive (+) and end on a negative (-) charge or ?.
Field lines can be used to show a graphical representation of electric fields. Practically visual obtaining of field lines can be shown with the help of an electrophore machine and electric sultans.
In turn, connecting the electric sultans with the electrophore machine, we get a clear demonstration of the graphical representation of electric fields. Simultaneously with the experiment, a graphical representation of the field is projected onto the screen with the help of a codoscope.
I. Single charge field: (demonstration)
a) field of a single positive charge: (graphical representation)
b) Field of a single negative charge:
c) the field of two opposite charges (experiment)
d) the field of two opposite charges (graphical representation)
c) the field of two similar charges (experience)
d) the field of two similar charges (graphical representation)
It must be said that, unlike other vector quantities, tension, as a vector quantity, is characterized not by the length of the vector, but by the density of drawing lines of tension per unit area. (via overhead projector - a graphic image showing this is shown on the screen or on the board)
III. Work to consolidate and control knowledge
Physical dictation:
1. The law of conservation of electric charge (formula)
2. Coulomb's law (formula)
3. The type of matter that carries out the interaction of charged bodies located at a certain distance from each other (Electrostatic field)
4. Unit of charge (1 C)
5. Instrument for detecting electric field (Electrometer).
6. The formula of the electric field strength (.
7. The unit of measurement of tension ().
8. What instrument did Sh. Coulomb use to study and derive his law? (By torsion dynamometer or torsion balance).
9. Power characteristic of the electric field (Tension).
10. Show a graphical representation of the electric field of a single positive charge.
Collect student responses.
IV. On the board is prepared, while closed from students, a brief record of the problem that needs to be solved.
Task: A force of 0.015 N acts on the charge C at a certain point in the electric field. Determine the field strength at this point.
Given: Solution:
V.Summing up the lesson
v. Homework § 92-93
View document content
"Physics lesson. The theme of the lesson is "Electric field. Tension. The idea of short-range action." »
Physics lesson. Topic: Electric field.
Near action and action at a distance
Spreads
with the final
speed
Spreads instantly
Interaction through the void
Interaction through the field
Electric field
Idea: M. Faraday
Theory: J. Maxwell
q 1
q 2
close interaction
t is the transmission time of electromagnetic interactions
r is the distance between charges
s is the propagation speed of electromagnetic interactions (300,000 km / s)
Electric field:
- financially: exists independently of us and our knowledge about it (radio waves)
- created by charges
Main property: acts on q with some F
Electric field strength
[E]==
The field strength is equal to the ratio of the force with which the field acts on a point charge to the module of this charge.
E T
- field strength of a point q 0
Principle of superposition of fields
E 2
E=E 1 +E 2 +E 3 + … + En
E 1
The field of a charged ball.
Inside the ball E=0
+ + - + E= const homogeneous email field Lines of force: not closed; do not intersect; start at + q ; end in -q ; continuous; thicker; where E is greater. 7" width="640" Lines of force (SL - lines of tension) of the electric field
SL - continuous lines, tangent to which at each point. through which they pass coincide with E .
E= const homogeneous email field
Field lines: not closed; do not intersect; start on + q; end on -q; continuous; thicker; where E more.
Lesson 57 Topic: Electric field. Electric field strength. Principle of superposition of fields Target: disclosure of the material nature of the electric field and the formation of the concept of electric field strength
Lesson objectives: to acquaint students with the power characteristic of the electric field;
∙ to form informal knowledge in the interpretation of the concept of “electric field strength;
∙ to cultivate a conscious attitude to learning and interest in the study of physics.
Lesson: learning new material Equipment: light metal foil sleeve, plexiglass stick, sultans on a stand, electrophore machine, ball on a silk thread, capacitor plates, presentation, flash animation Lesson progress
- Repetition of what has been learned
- Formulate Coulomb's law physical meaning coefficient k? Determine the limits of applicability of Coulomb's law?
- Physical dictation. The law of conservation of electric charge. Coulomb's law. (mutual verification)
Learning new material
- Learning new material
- E.P. tension
E.P. tension does not depend on the magnitude of the charge, the vector quantity (power characteristic of the field) It shows with what force the field acts on the charge placed in this field. 
Substituting the expression for the force into the formula, we obtain an expression for the field strength of a point charge
How can one characterize the field created by several charges? It is necessary to use the vector addition of forces acting on the charge introduced into the field and we will obtain the resulting E.P. This case is called the SUPERPOSITION PRINCIPLE( slide 6)Experiment 4 Experiments on demonstrating the spectra of electric fields. (1. Experiments with sultans mounted on insulating tripods and charged from an electrofoil machine. 2. Experiments with capacitor plates, to which paper strips are glued at one end.) It is convenient to depict the electric field with graphic lines - POWER LINES. LINES OF FORCE are lines indicating the direction of the force acting in this field on a positively charged particle placed in it ( slides 9,10,11)
Field lines of the field created by positively (a) and negatively (b) charged particles 
The most interesting case is E.P. created between two long charged plates. Then a homogeneous E.P. is created between them. + - 1 2 3Explanation of the principle of superposition, using a graphical representation ( slides 11,12,13)
III.Consolidation of knowledge, skills, skills
Review questions
∙ Analysis of questions:
a) How should we understand that there is an electric field at a given point?
b) How should we understand that the tension at point A is greater than the tension at point B?
c) How is it to be understood that the strength at a given point of the field is 6 N/cl?
d) What value can be determined if the intensity at a given point of the field is known?
∙ 2. Analysis of qualitative tasks
800. Two charges of the same modulus are at some distance from each other. In which case is the intensity at a point lying halfway between them greater: if these charges are of the same name or opposite? (Opposite. With the same point charges, the intensity will be zero.)
801. Why do birds fly off the high voltage wire when the current is turned on? (When a high voltage current is turned on, a static electric charge arises on the bird's feathers, as a result of which the bird's feathers bristle and diverge (like the brushes of a paper sultan connected to an electrostatic machine diverge). This frightens the bird, it flies off the wire.)
∙ Analysis of calculation problems [Rymkevich A.P. Collection of problems in physics, 10-11 cells. - M .: Bustard, 2003.]:
698. At some point in the field, a force of 0.4 μN acts on a charge of 2 nC. Find the field strength at this point. (200 V/m)
699. What force acts on a charge of 12 nC placed at a point where the electric field strength is 2 kN/Cl? (24 µN)
Summing up the lesson.
Literature:
Textbook Physics 10, B. Krongar, V. Kem, N. Koishibaev, publishing house "Mektep" 2010
[Tulchinsky M.E. Qualitative problems in physics in high school. - M .: Education, 1972.]:
Rymkevich A.P. Collection of problems in physics, 10-11 cells. - M .: Bustard, 2003
V.A.Volkov. To help the school teacher.
Topic: Electric field. Electric field strength. Principle of superposition of fields
Target: disclosure of the material nature of the electric field and the formation of the concept of electric field strength
Lesson objectives: to acquaint students with the power characteristic of the electric field;
∙ to form informal knowledge in the interpretation of the concept of “electric field strength;
∙ to cultivate a conscious attitude to learning and interest in the study of physics.
Lesson: learning new material
Equipment: light metal foil sleeve, plexiglass stick, sultans on a stand, electrophore machine, ball on a silk thread, capacitor plates, presentation, flash animation
During the classes
Repetition of what has been learned
Formulate Coulomb's Law
What is the physical meaning of the coefficient k?
Determine the limits of applicability of Coulomb's law?
Physical dictation. The law of conservation of electric charge. Coulomb's law. (mutual verification)
Learning new material
1. Is it possible to create an electric charge?
2. Do we create an electric charge during electrification?
3. Can a charge exist separately from a particle?
4. A body, the total positive charge of the particles of which is equal to the total negative charge of the particles, is ... ..
5. The strength of the interaction of charged particles with an increase in the charge of any of these particles ... ..
6. When a charge is placed in a medium, the force of interaction between them….
7. With an increase in the distance between charges by 3 times, the interaction force……
8. The quantity characterizing the electrical properties of the medium is called ...
9. In what units is the electric charge measured?
(1, Yes; 2. No; 3. No; 4. Neutral; 5. Increases; 6. Decreases; 7. Reduced by 9 times; 8. Dielectric constant; 9. In pendants)
Learning new material
The interaction of charges according to the Coulomb law is an experimentally established fact. ( slide 1 )However, it does not reveal the physical picture of the interaction process itself. And it does not answer the question of how the action of one charge on another is carried out.
Experiment 1 (with a sleeve) We slowly bring a vertically located plexiglass plate to a light metal foil sleeve suspended on a thread, having previously charged it by rubbing it with wool.
-What's happening?( there is no contact, but the sleeve has deviated from the vertical)
Experiment 2 ( electrophore machine, plates of a spherical capacitor, a tennis ball suspended on a silk thread ) After charging the plates, we observe the movement of the ball between them. Why?
This is how communication works at a distance. Maybe it's the air that is between the bodies?
Experiment 3 (watching a video fragment, flash animation) Pumping out the air, we observe that the leaves of the electroscope are still repelled from each other.
What can be the conclusion? ( air does not participate in the interaction )
How then is the interaction carried out?
Faraday gives the following explanation:
There is always an electric field around every electric charge. ( slide 2)
To characterize E.P. you need to enter the values.
The first characteristic of the Field is INTENSITY.
Let us turn again to Coulomb's law ( slide 3 )
Consider the action of the field on the charge introduced into the test charge field.
……………………………………………
Thus, if we look at the ratio, we will get a value that will characterize the action of the field at a given point.
Designated with the letter E.
E.P. tension
E.P. tension does not depend on the magnitude of the charge, vector quantity (force characteristic of the field) It shows with what force the field acts on a charge placed in this field.
Substituting the expression for the force into the formula, we obtain an expression for the field strength of a point charge
How can one characterize the field created by several charges?
It is necessary to use the vector addition of forces acting on the charge introduced into the field and we will obtain the resulting E.P. This case is called the SUPERPOSITION PRINCIPLE.
(slide 6)
Experiment 4 Experiments to demonstrate the spectra of electric fields. (1. Experiments with sultans mounted on insulating stands and charged from an electrofoil machine. 2. Experiments with capacitor plates, to which paper strips are glued at one end.)
The electric field is conveniently depicted by graphic lines - LINES OF FORCE. LINES OF FORCE are lines indicating the direction of the force acting in this field on a positively charged particle placed in it ( slides 9,10,11)
Field lines of the field created by positively (a) and negatively (b) charged particles
The most interesting case is E.P. created between two long charged plates. Then a homogeneous E.P. is created between them.
Explanation of the principle of superposition, using a graphical representation ( slides 11,12,13)
III. Consolidation of knowledge, skills, skills
Review questions
∙ Analysis of questions:
a) How should we understand that there is an electric field at a given point?
b) How should we understand that the tension at point A is greater than the tension at point B?
c) How is it to be understood that the strength at a given point of the field is 6 N/cl?
d) What value can be determined if the intensity at a given point of the field is known?
∙ 2. Analysis of qualitative tasks
800. Two charges of the same modulus are at some distance from each other. In which case is the intensity at a point lying halfway between them greater: if these charges are of the same name or opposite? (Opposite. With the same point charges, the intensity will be zero.)
801. Why do birds fly off the high voltage wire when the current is turned on? (When a high voltage current is turned on, a static electric charge arises on the bird's feathers, as a result of which the bird's feathers bristle and diverge (like the brushes of a paper sultan connected to an electrostatic machine diverge). This frightens the bird, it flies off the wire.)
∙ Analysis of calculation problems [Rymkevich A.P. Collection of problems in physics, 10-11 cells. - M .: Bustard, 2003.]:
698. At some point in the field, a force of 0.4 μN acts on a charge of 2 nC. Find the field strength at this point. (200 V/m)
699. What force acts on a charge of 12 nC placed at a point where the electric field strength is 2 kN/Cl? (24 µN)
Summing up the lesson.
Literature:
Textbook Physics 10, B. Krongar, V. Kem, N. Koishibaev, publishing house "Mektep" 2010
[Tulchinsky M.E. Qualitative problems in physics in high school. - M .: Education, 1972.]:
Rymkevich A.P. Collection of problems in physics, 10-11 cells. - M .: Bustard, 2003
V.A.Volkov. To help the school teacher.
Lesson type: problem-developing
The purpose of the lesson: Create conditions for:
- formation of ideas about the electric field and its effect on the body; electric force and its dependence on the distance between bodies.
- development of communicative competence through the ability to analyze, compare, draw conclusions;
- education of tolerance and conscious attitude to teaching.
Equipment:
- wooden ruler,
- glass and ebonite rod,
- electrostatic sleeves,
- portraits of D. Maxwell, O. Coulomb.
Lesson technology: dialog.
Forms of study: frontal, group, individual, in pairs.
Teaching methods: verbal and practical.
Stroke lesson
1. Organizational moment(1 min.)
Experience: the ruler lies on the back of the chair so that it is in balance. An ebonite charged stick is taken and slandered to the ruler without touching it. The line comes out of rest.
2. Actualization of knowledge.
- How can you explain the results of the experience?
- Why is the ruler moving?
When studying mechanics, we learned that the action of one body on another occurs directly during the interaction of bodies, and in this experiment we do not observe contact, but we observe movement.
- How to explain the interaction of bodies in this case?
We write down the key words on the board strength, interaction.
- It can be assumed that a space with special properties exists around a charged body. There is a problem that needs to be solved.
Writing on the blackboard on the left (sign?).
Let's designate the goals of our lesson (students formulate the goal of the lesson, and the teacher specifies). Experience is shown to solve the problem. A charged body ebonite rod approaches a quietly hanging sleeve, and then a glass one, while the distance between the sleeve and the charged body changes. The results of the experiment are analyzed by students.
Board writing:
- Repulsion.
- Attraction.
- What determines the force with which electrical bodies interact?
Writing on the board. From distance.
- How do they interact? (students conclude: the closer the distance between the bodies, the stronger the interaction forces and vice versa).
Having looked at and analyzed the experiments, we have studied how the interaction of charged bodies occurs, and by what means this interaction occurs, we still do not know.
Teacher: Many scientists have studied the interaction of charged bodies, but M. Faraday and D. Maxwell, O. Coulomb made a special contribution. As a result, it was found that every charged body is surrounded by a special property of matter, which is called an electric field.
So what is this space with special properties, through which the interaction between charged bodies is carried out?
Writing on the board. Electric field.
A summary appears on the board.
Work with a textbook, with reference literature (students give a definition of the electric field, features of the electric field).
3. Systematization of knowledge.
Teacher: today in the lesson we got acquainted with a special type of matter that exists independently of us and our knowledge about it. And this is called an electric field that exists around a charged body and the field of one charge acts on the field of another charge with some force, and this force is called electric force (work with a reference abstract).
Group work, in one minute you must find a solution to the problem that you will be offered.
- K-1. How, using an electric field near a charged stick, to make a piece of cotton soar in the air? Show the experience and give it an explanation.
- K-2. Show the action of the electric field using the material at hand and give an explanation.
- K-3. During the general cleaning in the house, polished surfaces, glass, we wipe with a dry cloth made of synthetic fabric, and painted with oil paint - raw? Why do we think differently about cleaning?
And then you need to evaluate your work in the lesson. Test sheets are provided. Where you have to answer questions. Then you will let your classmate check your answers, where he will already give you a mark.
4. Stage of reflection.
Knowledge Test Sheet