Presentation on the topic “Electroscope electric field. Video lesson "Electroscope
AMPER (Ampere) André Marie (1775 - 1836), an outstanding French scientist, physicist, mathematician and chemist, after whom one of the main electrical quantities is named - the unit of current strength - ampere. The author of the term "electrodynamics" as the name of the doctrine of electricity and magnetism, one of the founders of this doctrine.
PENDANT (Coulomb) Charles Augustin (1736-1806), French engineer and physicist, one of the founders of electrostatics. Investigated the deformation of the torsion of threads, established its laws. Invented (1784) torsion scales and discovered (1785) the law named after him. Established the laws of dry friction.
Faraday Michael (September 22, 1791 - August 25, 1867), English physicist and chemist, founder of the theory of the electromagnetic field, member of the Royal Society of London (1824).
James Clerk Maxwell (1831-79) - English physicist, creator of classical electrodynamics, one of the founders of statistical physics, predicted the existence electromagnetic waves, put forward the idea electromagnetic nature light, established the first statistical law - the law of the distribution of molecules by speed, named after him. Developing the ideas of Michael Faraday, he created the theory electromagnetic field(Maxwell's equations); introduced the concept of displacement current, predicted the existence of electromagnetic waves, put forward the idea of the electromagnetic nature of light. Established a statistical distribution named after him. Investigated the viscosity, diffusion and thermal conductivity of gases. Maxwell showed that the rings of Saturn are composed of separate bodies.
Goals:
students' knowledge of the electrification of bodies,
form students' perceptions of
electric field and its properties, introduce
with an electroscope (electrometer) device.
developing skills to draw more general conclusions and
generalizations from observations.
worldview ideas, the cognizability of phenomena and
properties of the surrounding world, increasing
cognitive interest of students with
using ICT.
After the lesson, the student knows:
- The structure and purpose of the electroscope
(electrometer). - Concepts electric field, electric forces.
- Conductors and dielectrics.
- Identify and systematize what they have
knowledge about the electrification of bodies. - Explain the action of an electric field on
included in it electric charge. - Deepens knowledge about the electrification of bodies.
- Develops intellectual skills.
Lesson structure:
- organizational stage.
- Repetition in order to update previous knowledge.
- Formation of new knowledge.
- Consolidation, including the application of new knowledge in
changed situation. - Homework.
- Summing up the lesson.
- Electroscope (1 copy).
- Electrometer (2 copies), metal
conductor, ball. - Electrophore machine.
- "Sultans".
- Glass and ebonite rod; (wool, silk).
- Presentation.
| Structural elements of the lesson | Teacher activity | Student activities |
| Organizing time | Ensures overall student readiness to work. | Listen to teachers. |
| Motivational - indicative | In order to repeat the material, learned in the previous lesson, conduct a brief front poll: 1. What are the two types of charges
Can the same body, for example ebonite Is it possible, when electrified by friction, to charge Is the expression correct: “During friction, 2. Offers to perform a test in writing | 1. Answer questions. 2. |
| Formation of new knowledge | The electrification of bodies can be carried out not only by friction, but also by contact. Demonstration of experience (for illustration theoretical conclusions): a) bring nael. b) the sleeve is attracted, and then repelled, c) checking for the presence of a negative charge on | Listen to the teacher, observe the progress experience, which serves as the starting point for experimental substantiation of electrization upon contact, participate in the conversation. Do notes in a notebook. |
| On the reviewed physical phenomenon based on the operation of devices such as electroscope and electrometer. Demonstration instruments a) electroscope instrument for detecting email charges; Their design is simple: plastic stopper in a metal frame passes through a metal rod, at the end which two sheets of thin paper are fixed. The frame is covered with glass on both sides. Demonstrating the device and principle of operation electroscope, the teacher asks students questions: how As for the angle of divergence of the leaves of the electroscope For experiments with electricity, use and | Listen to the teacher, observe the progress experiment, answer questions, find similarities and differences in the device and principle operation of devices, draw conclusions. |
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| Distinguish between substances that are conductors and non-conductors of electrical charge. Experience demonstration: charged the electroscope is connected to an uncharged first metal conductor, and then glass or ebonite rod, in the first case the charge passes, but in the second does not pass to uncharged electroscope. | Listen to the teacher, work with the textbook (p. 27 - p. 63), get acquainted with the conductors and dielectrics of electricity, draw conclusions from experience (identification of the second level of knowledge acquisition) |
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| All bodies that are attracted to charged bodies - are electrified, which means they forces of interaction act, these forces are called electric (forces with which el. Field applies to the email entered into it. Charge. Anything a charged body is surrounded by an electric field (special kind matter different from matter). The field of one charge acts on the field of another. | Listen to the teacher, write in a notebook, in answer questions during the conversation. |
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| Repetition and systematization knowledge | Conversation on questions to paragraphs 27, 28: | Answering questions (revealing third level of knowledge acquisition) decide quality tasks, applying knowledge in a new situations. |
| Like with pieces of paper detect if the body is electrified? |
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| Describe the device of the school electroscope. |
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| As for the angle of divergence of the leaves electroscope judge its charge? |
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| What is the difference between space surrounding electrified body, from space surrounding the non-electrified body? |
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| Decision quality objectives (application of knowledge in a new situation). |
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| Why is the rod of an electroscope always make metal? |
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| Why does the electrometer discharge if touch its ball (rod) with your fingers? |
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| In an electric field uniformly charged ball in t. A is charged speck of dust. What is the direction of the force acting on a speck of dust from the side of the field? |
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| Does the field of a dust particle act on the ball? | ||
| Why the lower end of the lightning rod need to be buried in the ground, working earthing appliances? |
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| Will they interact closely located electric charges in airless space (for example, on the moon, where no atmosphere) |
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| Organization of homework. | Read and answer questions p. 27-28. Invites students to make their own electroscope. | Recording homework in diaries exercise. |
| reflective | The teacher asks the students to answer questions: what question was the most interesting, the simplest, the most difficult. | They answer questions. |
Lesson Objectives: To get acquainted with the device of the electroscope. Get to know the electroscope. Introduce the concepts of conductors and dielectrics. Introduce the concepts of conductors and dielectrics. To form an idea about the electric field and its properties. To form an idea about the electric field and its properties. Convince yourself of the reality of the existence of an electric field on the basis of experiments that reveal the basic properties of an electric field. Convince yourself of the reality of the existence of an electric field on the basis of experiments that reveal the basic properties of an electric field.
What two types of charges exist in nature, what are they called and denoted? How do bodies with like charges interact with each other? How do objects with opposite charges interact with each other? Can the same body, for example, an ebonite stick, be electrified by friction, either negatively or positively? Is it possible to charge only one of the contacting bodies during electrification by friction? Justify the answer.
We know that sticks made of rubber, sulfur, ebonite, plastic, and cardboard are charged by rubbing against wool. Does it charge wool? a) Yes, because Electrification by friction always involves two bodies, in which both are electrified. b) No, only sticks are charged.
Homework Read and answer questions n Creative task: make a homemade electroscope.
Why is the shaft of an electroscope always made of metal? Why does an electrometer discharge when you touch its ball (rod) with your fingers? Will closely spaced electric charges interact in airless space (for example, on the Moon, where there is no atmosphere)? Why does the lower end of the lightning rod need to be buried in the ground, while working electrical appliances should be grounded?
In the electric field of a uniformly charged ball at point A there is a charged speck of dust. What is the direction of the force acting on the dust grain from the side of the field? Does the field of a dust particle act on the ball? In the electric field of a uniformly charged ball at point A there is a charged speck of dust. What is the direction of the force acting on the dust grain from the side of the field? Does the field of a dust particle act on the ball? What is the difference between the space surrounding an electrified body and the space surrounding a non-electrified body? How is the charge of an electroscope judged by the angle of divergence of the leaves of an electroscope? How is the charge of an electroscope judged by the angle of divergence of the leaves of an electroscope?
slide 2
Electroscope
slide 3
matter substance field solid state liquid state gaseous state plasma electric magnetic gravitational nuclear
slide 4
Comparison of field and substance properties
substance 1. Impenetrable 2. Has volume and shape 3. Field is felt visually and tactilely 1. Mutually permeable 2. Not limited in space 3. Not perceived by the senses
slide 5
Electric field properties
1. Exists around charged bodies 2. Invisibly, determined by the action and with the help of instruments 3. Depicted using lines of force 4. The lines indicate the direction of the force acting from the field on a positively charged particle placed in it.
slide 6
What charge do the balls have?
Slide 7
Count...
How many excess electrons are contained in a body with a charge of 4.8 10-16 C? The same metal balls with charges -7q and 11q brought into contact and moved apart to the same distance. What are the charges of the balls? 3. If the body lacks five electrons, then what is the sign and charge module on it?
Slide 8
Check yourself:
1. Identical metal balls with a charge of 7e and 15e were brought into contact, then moved apart to the same distance. What was the charge of the balls? 2. Is it possible to say that the charge of the system is the sum of the charges of the bodies included in this system? 3. What is the name of the process leading to the appearance of charges on the body? 4. What is the structure of Rutherford's atom?
Slide 9
5. If the body is electrically neutral, does this mean that it does not contain electric charges? 6. If the number of charges in a closed system has decreased, does this mean that the charge of the entire system has decreased? 7. How do opposite charges interact? 8. How many types of charges does a gold atom contain? 9. What is the structure of the Thomson atom?
View all slides
§ 1 Electroscope and electrometer, principle of operation
There are devices with which you can detect the electrification of bodies, this is an electroscope and an electrometer.
An electroscope (from the Greek words "electron" and skopeo - to observe, to detect) is a device used to detect electric charges.
Purpose of the device:
charge detection;
Determining the sign of the charge;
Estimating the magnitude of the charge.
An electroscope consists of a metal rod to which two easily movable strips of paper or foil are suspended. The rod is fixed with an ebonite plug inside a cylindrical metal case, closed with glass covers.
The principle of operation of the electroscope is based on the phenomenon of electrification. When a rubbed glass rod (positively charged) comes into contact with a device (electroscope), electric charges will flow through the rod to the leaves. Having the same charge sign, the bodies will start to repel, so the leaves of the electroscope will diverge at a certain angle. The consumption of leaves at an angle of a larger value occurs when a larger charge is imparted to the electroscope, which means that it leads to an increase in the repulsive force between the bodies (Fig.). Therefore, by the angle of divergence of the leaves, you can find out about the magnitude of the charge of the electroscope. If a body with a negative charge is brought to a positively charged device, we will notice that the angle between the leaves will decrease. Conclusion: the electroscope makes it possible to find out the sign of the charge of the investigated body.
In addition to the electroscope, one more device can be distinguished - an electrometer. The principle of operation of the devices is practically the same. The electrometer has a light aluminum pointer, with the help of which, by the angle of deviation, one can find out the amount of charge that has been imparted to the electrometer rod.
§ 2 Electric field and its characteristics
Bodies are electrified as follows: they transfer a positive or negative charge to them, increasing or decreasing the magnitude of the charge. In this case, bodies acquire different properties and are able to attract or repel other bodies. How does the body "understand" that the charge of another must be attracted or repelled? To answer this question, you need to find out a special form of matter - the "electric field".
Let's electrify with the same name (of the same sign) a metal ball on a plastic stand and a light cork ball on a thread (let's call it a test ball). We will move it to different points in space around a large ball. We will notice that at every point in space around an electrified body, a force is found acting on the test ball. The fact that it exists is observed by the deviation of the ball thread. As the ball moves away from the test ball, the ball on the thread deviates less, therefore, the force acting on it becomes less and less (by the angle of deviation of the thread from the equilibrium position).
So, at every point in space around electrified or magnetized bodies there is a so-called force field that can affect other bodies.
An electric field is a special kind of matter created by an electrically resting charge and acting with some force on a free charge placed in this field.
Field characteristics:
1. It is material, as it acts on material objects (light free body- sleeve).
2. It is real, as it exists everywhere and even in a vacuum (airless space) and independently of a person.
3. Invisibly and does not affect the human senses.
4. Does not have a specific size, border, shape.
5. Occupies all the space surrounding a given charged body.
6. As you move away from the charge, the field weakens.
7. Possesses energy.
8. For electric fields, two principles are inherent: the principle of independence (if there are several fields, then each field exists independently of the other), the principle of superposition (superposition) - the fields do not distort each other.
9. There is about a charged body, particles. Every charged body has its own electric field around it.
10. A field is detected by the action of a certain force on a freely suspended charged body, this force is called electric.
§ 3 Electric field lines
To graphically represent the field and find out its direction of propagation, it is necessary to use the method of field lines.
To do this, let's do an experiment.
Let's take two metal balls on plastic stands, as well as a needle, also mounted on a stand. We place the balls at a distance of 40-50 cm from each other, and between them - a stand with a needle. We balance a dry wooden chip on it. As you can see, the balls have different charge signs, we will see that the sliver will turn around so as to be on the straight line connecting the balls (see the top of the figure).
If we place a chip in different positions near the balls (see the figure), we note that it will take a position on the mentally drawn arcuate lines connecting the balls; this is what the electric field lines look like.
Let's demonstrate an interesting case: there are charged bodies. We place glass above them, and pour finely chopped hairs on the surface of the glass. Under the action of the field, they begin to orient themselves in an interesting way, a “picture” appears showing the location of the bodies. (see pictures below). Left and right, they are oriented around positively and negatively charged particles, and in the central part - around oppositely charged balls.
The lines of force are depicted as more “frequent” lines where a larger electric charge is found, and hence a large electric force when exposed to given field on the body. The model of lines of force shows the magnitude of the force and the direction of the field on particles placed in the field.
There is a device with which you can find out the magnitude and sign of the charge, which is important in electrical phenomena. Also, the electric field is "connected" to the charge. When the charge moves in the other direction, the field instantly follows it.
List of used literature:
- Physics. Grade 8: Textbook for educational institutions / A.V. Peryshkin. – M.: Bustard, 2010.
- Physics 7-9. Textbook. I.V. Krivchenko.
- Physics. Directory. O.F. Kabardin. - M.: AST-PRESS, 2010.
