Educational portal. Experiments on electrostatics Determination of the sign of the charge
Seletkov Mikhail
This work introduces students to static electricity, some of its properties, with interesting facts about the use of static electricity. The course of the experiments included in the work is described in detail. The work can be useful for students in the lessons of the surrounding world and physics.
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INTRODUCTION
Modern life is unthinkable without radio and television, telephones, computers, all kinds of lighting and heating devices, machines and devices, which are based on the possibility of using electricity. And just 200 years ago, very little was known about electricity. I learned that the science of electricity began with the study of static electricity. I wondered what static electricity was and wanted to do some experiments with electricity myself. So there was goal of the work :
Learn what static electricity is, empirically test its properties.
For this, it was necessary to solve the following tasks :
1. Study the literature on static electricity
2 Select and conduct the necessary experiments, create a conditional model of the electroscope
3. Find out how knowledge about static electricity is applied in the modern world
When working, I used the following methods:
Analysis of scientific and educational literature
Observation
Finding information on the Internet
Experiments
Construction
Photography-illustration
From the history of electricity
The first important discoveries and inventions in the field of electricity were made in the 17th and 18th centuries. But for the first time, people showed interest in electricity back in the 6th-7th centuries. BC NS. So the philosopher Thales from Miletus noticed that if amber is rubbed with wool or fur, it will begin to attract specks and threads. I have done a similar experience. Indeed, if you rub amber with wool, small particles are attracted to it. Why is this happening? In those distant times, there was no correct explanation for this phenomenon. Many centuries later, in 1600, the physician to Queen Elizabeth of England, William Hilbert, wrote the first scientific work on electricity and electrification by friction. He discovered that instead of amber, you can take diamond, sapphire, glass and other materials that, like amber, will attract light particles. He called these substances electrical (from the Greek word "electron", as the Greeks called amber). Therefore, subsequently, about bodies that, after rubbing, acquire the property of attracting other bodies to themselves, they began to say that they are electrified. But for several centuries, scientists tried to find out why objects are electrified and how it happens, until they discovered the secrets of this mysterious phenomenon inside the atom.
experimental part
Everyone knows this phenomenon: if you take off synthetic clothes, you will hear a slight crackle, and in the dark you can even see faint sparks, besides, threads, hairs and other small particles easily stick to synthetic clothes. All of these examples relate to a phenomenon called static electricity.
Static electricity- This is a phenomenon associated with the appearance of stationary electric charges in the body.
Static electricity has been proven to be caused by friction. I was convinced of this, by the example of experience
Experience 1.
Materials:
Glass stick
Plastic bag
Small pieces of paper
Progress
1. Take a glass stick and hold it to small light particles of paper. Nothing happens. This means that glass is electrically neutral in its normal state.
2.Then I will rub the glass rod with a plastic bag. Pieces of paper will immediately be attracted to her. This means that the wand has become electrified.
Conclusion: electrification occurs due to friction.
But how does this happen? The answer is found in the structure of the substance. All substances in nature are made up of tiny particles called atoms. Atoms, in turn, consist of even smaller particles: "+" charged protons located in the center of the atom and electrons, which are charged "-" and are located farther from the center. The positive and negative charges in an atom are equal in magnitude, and in general the atom is electrically neutral. When we rub two objects against each other, one of them captures individual electrons from the surface of the other and receives a negative charge. An object that has lost some of its negative particles becomes positively charged. This means that all bodies are electrified either negatively or positively. It was proposed to consider the charge of an electrified rod made of plastic (ebonite) negative, and the charge of a glass rod positive. It is known that like charges repel, and unlike charges attract. I was able to verify the reliability of this law in the course of the experiment.
Experience 2.
Materials:
Rack fixture
Foil balls
Glass stick
Plastic bag
Ebony stick
Woolen fabric
Progress
1. Rub a glass stick on polyethylene and bring it to the ball.
2. I do the same with an ebony stick, worn against wool.
I saw that the ball was attracted to the electrified stick.
3. Then I place two closely spaced pieces of foil on the counter and touch both pieces with an ebonite stick. They will push off.
4. I touch both pieces with a glass rod. They will push off
5. Now I will touch one piece of foil with a glass stick, and the other with an ebony one. They will be attracted to each other.
1.Conclusion : Electricity can attract and repel, the same charges repel, and different ones are attracted to each other.
During the experiments, I noticed that the electrification of the object quickly ceases. Why does it depend? The reason for this is that the extra electrons attached to the atom are either scattered in the air or go to other bodies. Such bodies, which conduct electricity well, are called conductors. Thus, all substances are divided into conductors and dielectrics. This can be verified by experience.
Experience 3. Materials:
Ebony stick
Plastic ballpoint pen
- Wooden pencil
- Eraser
- Metal spoon
- Small pieces of paper
Progress
1. At the counter, I hung a ballpoint pen, a wooden pencil, and a piece of rubber on a thread. He spread small pieces of paper on the table. 2. With the charged stick touched the top of the pen, pencil and rubber. Nothing happens.
3.Hang a metal spoon on the counter. When he touched the top of the spoon, the scraps of paper on the table stirred and jumped. This means that the charge from the upper part of the spoon spread throughout the entire spoon.
Output : Metal conducts electricity well, but rubber, wood and plastic do not.
Now I understand why wires are made of metals, and so that the charge does not "go away" where it should not be, they are dressed in a sheath made of rubber or plastic.
So, all substances in nature are divided into conductors and non-conductors, in addition, there are two types of electric charges, the same ones repel, and the opposite ones attract. It is possible to find out whether a body is a conductor or a dielectric, whether it has an electric charge, its magnitude and sign, using a special device - an electroscope. I was able to construct a primitive model of an electroscope. (See the appendix for the appearance of the model) I did some experiments with the electroscope.
Experience 4.
Materials:
Ebony stick
Woolen fabric
Glass stick
Plastic bag
Wooden ruler
Plastic ruler
Experience 4.1.
Progress
1. I touch the electroscope with a charged ebony stick. The leaves instantly disperse, as if repelling each other. This is due to the fact that they received a negative charge of the same name, transferred from the ebony stick.
2. I touch the metal wire with my hand. The leaves fall off. The charge goes into the hand.
3. I touch the wire with a wooden ruler rubbed with wool. Nothing happens.
Conclusion: With the help of an electroscope, I saw that the human body conducts electricity well, and the tree is not electrified and is a dielectric.
Experience 4.2.
Progress
1. Take a plastic ruler, rubbed with wool and touch the electroscope. The leaves diverge.
2. Now I touch the electroscope with a charged ebony stick. The discrepancy has increased. This is clearly seen on our conventional scale. This means that the charge on the plastic ruler is the same as the charge on the ebony stick. The stronger the electric charge, the more the leaves diverge.
Conclusion: With the help of an electroscope, you can determine the charge of a body if the charge of another body is known.
Experience 4.3.
Progress
1. I touch the electroscope with a charged glass rod. The leaves diverge.
2. I bring a charged ebony stick to the electroscope. The leaves fall off instantly.
Output: a body whose charge is known can be discharged by a body charged oppositely.
Applying knowledge of static electricity.
Static electricity is a phenomenon that often occurs in nature, everyday life and technology. Everyone knows the most striking example of static electricity. This is lightning. During a thunderstorm, clouds rub against the air and are charged negatively. They attract the opposite charge to themselves, which accumulates on the soil, on trees, on houses. When the cloud charge becomes too large, an electrical discharge occurs - lightning, that is, a sharp and very strong movement of electrical charges from the cloud to the ground. Lightning is visible as a bright flash of light. It can be very dangerous. The first lightning rod (lightning rod) was invented by Benjamin Franklin in 1752. He realized that lightning is a huge discharge of energy and a pointed metal rod can attract this discharge to itself. Modern lightning rods have a grounded wire. Through it, electric charges go into the ground.
Man learned to apply knowledge about static electricity in other areas of his life and work. Here are some examples. When rubbing against the air, the plane is electrified. Therefore, after landing, a metal ladder is not immediately fed to the aircraft; a discharge may occur and cause a fire. First, the plane is unloaded: a metal cable connected to the skin of the plane is lowered to the ground and the discharge goes into the ground. The electrification of tires on a dry road also occurs. Therefore, not for beauty, metal chains are suspended from behind tank cars carrying flammable substances. Static electricity is also dangerous in industrial premises where there is a vapor or dust of combustible substances. There are cases when static electricity discharges in such rooms led to explosions and fires. A lot of troubles are caused by static electricity in everyday life. Motes adhere to clothes, especially synthetic ones, static electricity discharges are harmful to health and can damage household appliances such as a computer. Knowledge about the nature of static electricity has made it possible to invent many useful things in everyday life: air ionizers, antistatic agents for clothes, hair and linen conditioners, and so on. But static electricity can also be beneficial. On this principle, dust collectors are made in large factories. A negatively charged rod is attached to the factory chimney, and smoke particles that are positively charged are deposited on it. As a result, environmental pollution is reduced.
CONCLUSION
Working on the topic, I managed to achieve my goal. I learned what static electricity is, through experiments I tested some of its properties, got acquainted with interesting facts about the use of static electricity. I consider my work to be relevant and promising. For more than a decade, mankind has been looking for new sources of energy. Static electricity is also considered among such sources. That is why it is necessary to know well its properties and capabilities. My work can be useful for students in the lessons of the surrounding world and physics. The experiments I have carried out can serve as a basis for showing tricks. And designing various models in childhood often serves as an impetus for choosing a profession.
BIBLIOGRAPHY
1. Halperstein L.Ya. Entertaining physics: M: Publishing house "Rosmen", 1998
2. Puig M., Vives J. Physics School Atlas: M: "Rosmen", 1998
3. Tomilin A. Stories about electricity: M .: Det. lit., 1987
4. Zhukov V. Cognitive experiences at school and at home: M: "Rosmen", 2001
5. Big book of experiments / ed. A. Meiyani: "Publishing house" ROSMEN-PRESS ", 2004
6. T. Tit Scientific fun. Physics: experiments, tricks and entertainment: - M: AST: Astrel, 2008
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"Are familiar to every person now. Electricity is used in transportation, in our homes, in factories, factories, in agriculture, etc. But in order to understand what he is, you must first familiarize yourself with a large range of phenomena called electric.
Some of these phenomena were discovered in ancient times. The ancient Greek scientist Thales (VII-VI centuries BC) noticed that amber rubbed with wool begins to attract light pieces of other materials (straws, wool, etc.). Two thousand years later, the English physicist W. Hilbert (1544-1603) discovered that not only rubbed amber but also diamond, sapphire, glass and some other materials have a similar ability. He called all these substances electrical, that is, similar to amber (since the Greek word "electron" means "amber").
Subsequently, about the body, which after rubbing acquired the property of attracting other bodies to itself, they began to say that it electrified, or what is communicated to him. And the process of imparting an electric charge to the body began to be called electrification.
A physical quantity called electric charge, denote by the letter q:
q - .
The unit of electrical charge in SI is called pendant(1 Kl) in honor of the French physicist C. Coulomb (1736-1806). The definition of this quantity will be given in § 10.
A body that has q is not equal to zero, they call charged, and the body, which q equal to zero, - neutral(uncharged).
Let's turn to experience. Take a glass stick and bring it up to the small pieces of paper. We will see that nothing happens. This suggests that in its normal state, glass (like most other bodies) is electrically neutral. Now rub the stick on a piece of paper and again bring it to the pieces of paper. We will see how they will immediately be attracted to it (Fig. 1). This means that as a result of friction on the paper, the stick became electrified: its electric charge became non-zero.
A similar phenomenon can be observed when brushing dry hair. Hair pulling against the comb is also the result of electrification.
By bringing an electrified stick closer to a thin stream of water, one can make sure that not only solids, but also liquids are capable of attracting (Fig. 2).
Holding an electrified object to your hand or placing your hand near the screen of a working TV, on the surface of which there are also electric charges, you can hear a slight crackling, and in the dark you can sometimes see even small sparks. This is also a manifestation of electricity.
Electric charges arising from electrification by friction are sometimes called static electricity... Most often, it is harmless (for example, when you pull synthetic clothes over your head, shuffle your feet on the carpet, or fidget in a chair during class). But sometimes it can be dangerous too. For example, the electrification of a liquid when rubbing against a metal, on the surface of which it flows, should be taken into account when pouring gasoline from a tank. Failure to take special precautions to discharge the electrical charge could result in the gasoline igniting and exploding.
It should be remembered that as a result of electrification by friction, both bodies acquire an electric charge. For example, when a glass rod and rubber come into contact, both glass and rubber become electrified. Rubber, like a glass rod, begins to attract light bodies to itself (Fig. 3).
To electrify bodies, one touch is usually not enough. The bodies should, tightly pressed, rub against each other. This is done in order to reduce the distance between the bodies and at the same time increase the area of contact between them.
A glass stick that is rubbed against silk attracts light objects (such as pieces of paper). The same pieces will be attracted to the ebony stick, which is rubbed against the fur. Does this mean that the charges acquired by these bodies are no different from each other?
Let's turn to experiments. We electrify an ebonite stick suspended on a thread by rubbing it against the fur. Let us bring another similar stick close to it, electrified by friction against the same piece of fur. We will see that the sticks push off (fig. 4). Since the sticks are the same and electrified them by friction against the same body, it can be argued that they had charges of the same kind. Experience has shown that bodies with charges of the same kind repel each other.
Now we bring a glass stick, rubbed against silk, to an electrified ebony stick suspended by a thread. We will see that they will be attracted. If the glass rod had a charge of the same kind as the ebony rod, they would be repelled. We see attraction (Fig. 5). This means that the charge formed on the glass, rubbed against silk, is of a different kind than on ebony, rubbed against fur. Experience suggests that bodies with different kinds of charges are attracted to each other.
Approaching the suspended electrified ebony stick charged bodies made of various substances: rubber, plexiglass, plastic, nylon, etc., we will see that in some cases the stick is repelled from them, while in others it is attracted.
All these experiments show that there are two kinds of electric charges in nature.
A charge of the kind that occurs on glass worn against silk is called positive(+), and the charge of the kind that appears on amber worn against wool was called negative (-).
As a result of experiments on electrification, it was found that all substances can be arranged in rows in which the previous body is electrified by friction against the next body positively, and the next one is negative. For example, one of these rows: rabbit fur, glass, quartz, wool, silk, cotton, wood, amber, rubber.
The experiments described above show that the nature of the interaction of charged bodies obeys a simple rule: bodies with electric charges of the same sign mutually repel, and bodies with charges of the opposite sign mutually attract... More succinctly, this rule is formulated as follows: like charges repel each other, and unlike charges attract.
???
1. What is called electrification?
2. What Greek word comes from the term "electricity"?
3. Are one or both bodies electrified by friction?
4. What two kinds of electric charges exist in nature? From what experiments does it follow that there are really two of them?
5. Formulate a rule describing the nature of the interaction of charged bodies.
6. A piece of wood was rubbed on silk. What charges (according to the sign) appeared on a piece of wood and what on silk?
7. What is the name of the unit of charge?
8. After completing the experimental tasks, describe the experiments shown in Figure 6.
Experimental tasks.
1. Inflate a baby balloon, then rub it against wool, fur or your hair. Why does the ball start to stick to various objects and even to the ceiling?
2. Wrap the pencil with metal foil and carefully peel the sleeve off the pencil. Hang it on a silk or nylon thread. Touch the cartridge case with an electrified body, the charge sign of which is known. Then electrify other bodies (plastic handle, comb, glass cup, etc.) and, bringing them to the sleeve, determine the sign of the charge of these bodies. Write down the results of the experiments in a notebook.
S.V. Gromov, I.A. Homeland, Physics Grade 9
Lesson content lesson outline support frame lesson presentation accelerative methods interactive technologies Practice tasks and exercises self-test workshops, trainings, cases, quests homework discussion questions rhetorical questions from students Illustrations audio, video clips and multimedia photos, pictures charts, tables, schemes humor, jokes, jokes, comics parables, sayings, crosswords, quotes Supplements abstracts articles chips for the curious cheat sheets textbooks basic and additional vocabulary of terms others Improving textbooks and lessonsbug fixes in the tutorial updating a fragment in the textbook elements of innovation in the lesson replacing outdated knowledge with new ones For teachers only perfect lessons calendar plan for the year methodological recommendations of the discussion program Integrated lessonsIf you have any corrections or suggestions for this lesson,
ELECTROSTATIC EXPERIENCES
Equipment
To study the phenomenon of electrification of bodies, we will make sultans, sleeves, an electroscope and a "carousel" from a long ruler mounted on a light bulb. You will also need balloons, a table tennis ball and a plastic (polyvinyl) tube - such tubes are used to insulate wires, and greenhouse frames are also made of them. The larger the diameter, the more the tube is electrified. The tube can be replaced with a plastic comb, a ballpoint pen body, or a piece of styrofoam. Also stock up on woolen, fur, silk scraps, pieces of leather, plastic wrap..gif "alt =" (! LANG: http: //*****/2002/19/no19_07.gif" align="left" width="185" height="180">круглого карандаша, а кончик скрутите фантиком. Привяжите к кончику нитку длиной 30–40 см. Второй конец нитки закрепите на ковровом колечке или скрепке. Сделайте две такие гильзы. Хранить их удобно в футляре от фотопленки или в коробочке от «киндер-сюрприза». Сделайте также две гильзы из папиросной бумаги и еще один комплект – из пенопласта или пластика. В пенопласт легко воткнуть булавку, а к головке булавки удобно крепить нитку.!}
Remember, the sleeves should be light - the electrostatic forces are small. If the sleeves are wrinkled, they can be easily restored with a round pencil.
To carry out the experiments, you also need a stand for attaching the sleeves.
· Electroscope. Take any clear glass jar with a plastic lid and make a small hole in the lid, into which you insert a nail or thick wire. Bend the tip of the nail and secure a strip of foil or tissue paper folded in half on it (Fig. A).
You can make a miniature electroscope from a pharmacy vial. Take a copper wire and thread it through the stopper. Attach two pins to the end of the wire. To increase the capacity of the electroscope, roll the outer end of the wire into a snail (Fig. B).
Another way: take a plastic bottle, cut off its upper conical part, cover both the inside and the outside of the bottle with food foil, attach (you can use ordinary pharmaceutical rubber) to the outside of the "broom" of narrow strips of light paper (Fig. C).
· "Carousel". Place a long ruler on the stand - for comparison, take three: wood, metal and plastic. An ordinary burned-out light bulb in a jar of mayonnaise can serve as a stand (Fig. A). But it is better to make a stand from a glass bottle with a cork: insert a needle into the cork in the center, and put an inverted glass cup on the needle (Fig. B).
· Take a ping-pong ball and cover it with graphite (paint over with a simple pencil). The ball can be replaced with a chicken egg, after removing its contents, rinsing and drying thoroughly, but the eggshell is very fragile and requires careful handling.
· 
Arrow. A simplified version is a strip of paper folded in half, dressed on the tip of a needle inserted into an eraser (Fig. A). The arrow made according to the "pattern" (Fig. B) is more stable. Make the second arrow out of foil.
Experiments. Remember: there should be no water near the experimenter's table. Experiments on electrostatics do not work well in wet weather. Water is a good conductor, so static charges can drain quickly in humid environments.
Experiments
1. Rub the plastic stick against a piece of paper or thin plastic wrap. The bodies will stick to each other. This interaction is called electrostatic, and the rod became electrified. Two bodies are electrified at once: a sheet of paper (or plastic wrap) and a stick. Electrostatic interaction is explained by the redistribution of electrical charges.
2. Bring an electrified stick to the sultan made of "rain" or magnetic tape, but do not touch the sultan. The foil strips will reach behind the stick and move along with it. A sultan made of threads will behave similarly. We see electrification from a distance.
In the weaving industry, the electrification of the threads, which occurs due to their friction during the movement of the shuttle, is a big problem. Electrified threads get tangled, torn. To partially eliminate the undesirable effect in the workshops, high humidity is artificially maintained.
3. Charge the wand by rubbing it on any piece of cloth. Bring her to 
shredded pieces of paper. The leaves will stick to the stick, and will begin to "react" even before they come into contact with it. We say that the charge, creating an electric field around itself, acts at a distance on these pieces of paper and electrifies them.
If the size of the pieces of paper is significant and the force of gravity is commensurate with the electrical force, the sheets will only rise, they may even stand on the edge, but will not come off the table. With a comb electrified on the hair, you can place an 8x8 cm leaf vertically.
Experiment with scraps of thread, pieces of fabric, polyethylene, that is, with dielectrics. You will observe similar behavior.
Take pieces of foil or metallized film, i.e. metal conductors. Light pieces of foil will bounce, hit the charged stick and bounce off sharply. When in contact with an electrified stick, the foil is charged. Similarly charged bodies repel, which we observe. The experience with metallic confetti looks very impressive!
Clean your home: wipe dust from the TV screen, from polished furniture with a cloth. The dust will re-settle on these surfaces very quickly. The reason is the same electrification of the surface and the attraction of light dust particles to it.
Please note that linoleum floors collect dust very quickly. When we walk on the floor, we electrify it, so the dust actively settles on it. In addition, static electricity persists for a long time on linoleum. This amount of dust does not settle on wooden floors. Let's try to explain this.
Take a wooden stick and electrify it by rubbing it against the shreds. Bring an electrified wooden stick near a sultan or an electroscope - and make sure that the tree is weakly electrified. Here is the answer about dust on the wooden floor.
Let's check by experience how metals are electrified, for example, a metal ruler. Since the human body is a good conductor of electricity, wear a rubber glove, otherwise the charge on the ruler will not accumulate. Testing a charged ruler on a sultan or an electroscope shows that metals are poorly electrified.
All solids are electrified, but to varying degrees.
4. Bring an electrified stick or comb to the stream of water flowing out of the tap. The jet will be attracted to the stick. Consequently, liquids are also electrified. Electrification of flammable liquids due to friction during transportation is dangerous, therefore fuel tanks are grounded.
5. Soap bubbles are also electrified. But observing this phenomenon requires patience, since soap bubbles burst quickly, especially in an electric field. A simplified version of the experiment - blow out a bubble on a horizontal surface (semi-bubble) and slowly bring a charged stick. You will see how it stretches.
6. Swipe an electrified stick over a sheet of paper, a metal clip, scissors - you will hear a slight crackle, reminiscent of discharges. The same thing happens when you take off your synthetic clothing. All day she rubbed against your body - electrified - but your body was electrified too. The body received a charge of one sign, clothes - another. When disconnected, you hear a characteristic crackling sound and feel some tingling sensation. Tiny lightning bolts can even be seen in the dark. If you are wearing a synthetic fur coat, then touching metal objects, you feel a fairly strong electric discharge.
This does not happen in clothes made from cotton and natural fibers. Scientists have determined that it is harmful for the cells of a living organism to be in a charged state. Hence the conclusion: despite the convenience and relative cheapness of synthetic clothing, you should not get carried away with it.
7. Another colorful experience with electrification at a distance. Bring an electrified stick to a wooden "carousel" ruler. The ruler will polarize and begin to gravitate towards the stick. With a charged stick, you can make the ruler rotate.
Do this experiment with a metal ruler. Due to the phenomenon of electrostatic induction, the metal ruler will also be attracted to the stick and rotate behind it.
The situation is more complicated with plastic rulers. There are materials that will repel rather than be attracted to the charged stick. These are transparent polystyrene rulers. The phenomenon is explained by the fact that there are "frozen" charges in them. During the production process, when the material was still liquid, it was exposed to a random electric field, which caused charges to its surface. When the material cooled down, they lost their mobility. Materials with these properties are called electrets. (Physical encyclopedic dictionary. - M .: Soviet Encyclopedia, 1984, p. 862.)
8. Another variant of the experiment with a "carousel" made of a bottle and an inverted glass. Place the scissors open with the letter "X" on the glass. If you bring an electrified stick to them, then you can achieve the rotation of the scissors.
9. Place an electrified hairbrush on the stand. Bring your fingers to it - the comb will move! (The experience is described in the book .: Physics quizzes in high school. - M., 1977.) If the experiment fails, wet your hands.
Replace the hairbrush with a "strange" plastic ruler (see experiment 7). It can also be set in motion by bringing your fingers to it. Apparently, the material from which the ruler is made has static memory.
10. Hang the foil sleeve on the stand. Bring an electrified stick to it. The sleeve will start moving: first it touches the stick, then it will sharply fly off in the opposite direction. An attempt to re-touch the sleeve with an electrified stick will end in failure - it will go to the side. The fact is that, touching a charged wand, the cartridge case was charged with the same name, and the bodies of the same name were repelled, which we are convinced of.
To remove the charge from the cartridge case, it is enough to touch it with your hand. The human body is a good conductor of electricity.
Repeat the experiment, but with casings made of a different material. You will get the same result.
11. Hang two sleeves on a stand at a short distance from each other. Adjust the thread length - the sleeves should hang at the same level. Charge one of them. Start bringing the other closer. If the sleeves are fixed on rings, then this is not difficult to do. At the first moment, they will be attracted to each other, touch and scatter sharply in different directions. Continue to bring the rings together until they are in full contact, however, the sleeves will remain apart, at an angle to each other. Once again we are convinced: equally charged bodies are repelled.
Place a stick with the same charge sign between the sleeves - the sleeves will disperse to a greater angle. Move the stick - and the sleeves will "accompany" it. In this experience, we have three equally charged bodies repelling each other.
Place the sleeves some distance apart. Charge one of them. To determine which of them is charged, it is enough to bring your hand to the sleeve: an unloaded sleeve will not react to your hand, but a loaded one will be attracted to your hand!
12. Electric pendulum. For this experiment, you will need a metal shield, which is easy to make from a sheet of cardboard with metal foil taped to it. Place the foil sleeve between the screen and the electrified stick. You will observe the following picture: the sleeve will be attracted to the wand, bounce off sharply, hit the screen, again be attracted to the wand, etc., i.e., it will begin to vibrate. An uncharged sleeve is attracted to an electrified rod, touching it, charges, is abruptly repulsed like a similarly charged body and hits a metal screen, to which it gives off its charge. The process starts over again. Since the sleeve removes a large electrical charge, the oscillations are damped, so the wand must be constantly recharged.
If you use an electrostatic machine, you will observe continuous oscillations.
Repeat the experiment replacing the metal screen with a cardboard one. The sleeve touches the dielectric screen and "sticks" to it: the screen is polarized, that is, its surface facing the stick is charged positively, so the sleeve "stuck".
Electrical vibrations can be observed by hanging the sleeve on a pencil between two cut-off and foil-wrapped plastic bottles. Bring a charged stick at some distance to the installation. The sleeve will touch the electroscope closest to the stick, and will be charged from it with the same charge on the sign. Then, as a similarly charged one, it will push off from it, hit the second electroscope, give it a charge, be attracted to the first, etc. We will observe the oscillations of the sleeve, that is, the model of a "perpetual motion machine"!
13. Bring the charged stick to the electroscope. The pins (or leaves) of the electroscope will disperse. Hence, they turned out to be equally charged. Remove the wand - they will come together again. We observe the phenomenon of electrostatic induction (Fig. A).
Place an inverted metal tin can on the lid of the electroscope (Fig. B). Reapply the charged stick without touching the can. The leaves of the electroscope will not react in any way to the electric field. This means that there is no electric field inside the metal can. For this reason, the cases of many devices are metal - they shield devices from external electric fields, interference, unwanted signals.
14. Touch the metal rod of the electroscope with a charged stick - its leaves will disperse and remain in this position. This means that we have transferred the charge to the leaves. Electrify the stick again and touch the electroscope again - its leaves will deflect to a larger angle, since the charge on the electroscope has increased.
Cover the rod with a tin can and touch it with a charged stick - the electroscope leaves will not diverge more. Again we are convinced of the screening of the electric field.
15. Rubbing the plastic stick with a piece of scrap, touch the piece to the rod of the electroscope. The leaves will part at a small angle. Now touch with an electrified stick. The leaves will immediately drop. This means that the electroscope is discharged. Consequently, the stick and the shred had charges of the opposite sign.
16. Check by rubbing paper on paper, plastic on plastic, etc., to see if these substances are electrified.
17. Take a plastic ping-pong ball and bring a charged stick to it - the ball will obediently roll after it. Cover it with graphite to enhance the effect.
18. Take a plastic bottle covered with foil and place a strip of paper folded in half on the edge of the bottle. Bring the electrified stick once from the side of the paper strip and once from the opposite side of the cylinder. In the first case, the strip will be attracted to the stick, in the second, it will stick to the cylinder foil. Now charge the cylinder with an electrified stick. Repeat experiment. You will get the opposite result!
19. "Electric" compass. Take the paper arrow. Cover it with a glass jar on top. Rub a piece of wool over the glass in one place. The paper arrow will be attracted to this location.
Repeat the experiment with the clear plastic jar. Plastic is more easily electrified, and the effect is greater. Start turning the can - the arrow will also turn behind it.
Bring the charged stick to the arrow under the can. The arrow will react sensitively to a change in the position of the stick, i.e., to an electric field. Dielectrics do not screen electric fields.
Experiments with balloons are very spectacular.
20. Electrify the balloon by rubbing it on your hair. As you lift the balloon above your head, you will feel the hair pulling behind it. Isn't it a sultan?
21. Check how small objects stick to the electrified ball: paper, thread, metal foil, etc. The effect is greater than from an electrified stick. If you carry out the experiment with granulated sugar, salt, flour, then the ball will be covered with "snow".
22. Lean the electrified ball against a vertical wall or ceiling - it will hang in this position for a long time.
23. Take two balloons. Electrify them and place them on a smooth table surface. The balls will repel each other and prevent them from coming together. Please note: they lie on the table with the electrified side.
24. Take the strings of electrified balls in one hand. The "obstinate" balls fly in different directions. (This experience may not work with "heavy" balloons.)
Sometimes ordinary objects show supernatural abilities at first glance: a plastic stick can attract paper, just like a magnet attracts iron or styrofoam sticks to clothes. Static electricity is responsible for these small miracles.
Static electricity is generated by the interaction of electrically charged particles - negative electrons and positive protons of atoms. Bodies are usually in an electrically neutral state because they are composed of an equal number of evenly distributed negative and positive particles. However, gaining or losing electrons, neutral bodies can become charged.
Bodies are charged by friction (rubbing), which strips some substances of some of their electrons, making these substances positively charged. For example, rubbing a plastic stick with fur transfers electrons from the fur to the plastic. As a result, the plastic acquires a negative charge, and the fur - a positive one. If the negatively charged plastic is then brought close to the electrically neutral pieces of paper, they will begin to adhere to the plastic. The "magic" attraction is caused by the formation of a negative charge in the plastic.
Basic rule of electricity
The fundamental law of electricity states that charges of opposite sign (+ -) attract, and charges of the same name (++ or -) repel each other. The magnitude of the forces of attraction and repulsion depends on the distance: the closer the charged bodies are to each other, the greater the corresponding force.
Contactless electrification
If a negatively charged rod is held near a neutral body, the rod's charge will move the surface electrons of the body (blue cubes with a "-" sign) to its far side. The side of the body closest to the rod will become positively charged (pink cubes with a “+” sign).
Friction magic
Friction when rubbing a plastic stick with fur causes the stick to acquire electrons (-), creating a negative charge on it. After that, the stick will begin to attract the paper to itself.
Determination of the sign of the charge
Some materials contain an increased amount of "free" electrons, which can freely move between atoms (-). Other materials firmly bind their electrons to positively charged nuclei (+). When two materials, such as styrofoam and feathers, rub against each other, the one that contains the most free electrons (in this case, feathers) will lose them and gain a positive charge.
Fragment of the lesson on the topic: "Electrification of bodies"
Malgina Vera Borisovna, physics teacher,
Education Center №80 of the Central District of St. Petersburg
Keywords:experiments on electrifying bodies; with a minimum investment of time, get the maximum effect in the development of thinking, creative abilities of students; continue the formation of students' skills in making devices for experiments and experiments, conduct an experiment, plan their actions, argue their conclusions; fostering a sense of comradely mutual assistance, ethics of group work.
In order to organize the work of each student with the greatest return, it is suggested to bring to the lesson to conduct experiments the following materials: three balloons, 25cm nylon fabric, threads, plastic bag, tape or duct tape, three plastic combs, scissors, nylon stocking, metal paper clip, popcorn kernels, wool or fur, cocktail straw.
One experiment is conducted by a group of 2 students. A sheet with a description of the experience is issued for the group. The group conducts the experiment at the desk, prepares an explanation of the observed phenomenon and presents the experience to the whole class. If the description of the experience contains exercise, it is discussed by the whole class.
1. Phenomena of electrification of bodies.
Experiment "Static glue"
Materials:
* Ebony stick
*fur
* pieces of paper
* glass rod
*newspaper
Sequencing
With an ebony stick, touch the small pieces of paper lying on the table, and raise the stick - the paper pieces will remain on the table. This indicates that the force of gravitational interaction between the paper leaves and the stick is insufficient to attract them to the stick.
We rub the ebony stick on the bellows and bring it to the same pieces of paper - they will jump and stick to the stick, and after a while, bounce off it. Then we repeat the experiment, bringing a glass stick close to the pieces of paper, rubbing it with a newspaper. Papers are intensely attracted to the stick.
Explanation As a result of contact and friction with fur or silk, the ebony stick acquired a new quality, expressed, in particular, in the fact that it became capable of attracting light bodies to itself with a force much exceeding the force of gravitational attraction. The observed phenomenon is the electrification of bodies. When electrified, bodies acquire an electrical charge.
Experience "Everything can be charged"
Materials:
* three balls
* two threads 30 cm long
* a piece of woolen cloth or felt
*duct tape
*newspaper.
Sequencing
Attach one inflated balloon below the table surface. Rub the ball (more than 20 movements) with a piece of cloth. Let go of the ball and it will hang freely. Rub the second ball with a piece of wool. Take it by the end of the thread and bring it to the first one.
What will happen to the balls? Attach the second balloon close enough to the first so that it looks like they are flying apart from each other.
Explanation Most bodies initially have a neutral charge (i.e. have no charge). However, if they are rubbed with certain materials, they will acquire a positive or negative charge. This phenomenon is called electrification.
When rubbing a balloon with wool, invisible negative charges move from the wool to the balloon. As a result, the charge equilibrium of the ball is violated. Charges coming from outside will give the ball an overall negative charge. Once moved, the tiny charges will remain in place (hence the word static).
If two charged balls are at a great distance from each other, then their charges are not enough to act on each other. When approaching, the balls are repelled, because both are negatively charged. This force will cause them to scatter and stop at some distance from each other.
Exercise!
1) Bring the third charged ball to the first two. What shape do the repelling balls form as a result?
2) Electrify one ball on a newspaper and the other on a piece of woolen cloth. Hang them some distance apart. Why are they attracted?
3) Their interaction is especially clearly visible, if one of them is rolled on the surface of the table, then the other will roll behind it. Why?
Experience "Positive charge"
Materials (edit)
* 25cm nylon fabric
* scissors
* plastic bag
Sequencing
Cut out a piece of fabric. Fold the plastic bag in half and hold it in your hand. Place a piece of nylon fabric between these halves and run the bag over the nylon several times. What happens when you put the package away? What makes nylon behave this way?
Explanation Unlike wool, polyethylene does not give up its negative charges so easily. On the contrary, it is easier for him to acquire negative charges. When you run the bag over the nylon, negative charges flow to the polyethylene. This causes the nylon to acquire a positive charge. Since both halves of nylon have the same charge, they repel each other and separate.
Exercise!
Will a plastic bag be charged if rubbed with wool?
An experience"Turn the arrow"
Materials:
* Metal paper clip
* a piece of wool
* plastic comb
* paper
* scissors
Sequencing:
Unfold a paper clip as shown in the illustration. The unbent part of the paper clip should lie flat on the table. Draw the arrow below on a piece of paper and cut it out with scissors. Bend the arrow slightly along the dotted lines with the edges down. Where the lines intersect is the center of balance. Carefully place the balance arrow on the point of the staple.
Load the plastic comb with a piece of wool. Bring the comb to the versorium. What do you see? Can you make the arrow make a complete revolution around its axis?
Explanation A charged comb induces a positively charged area on the arrow. This positively charged area and the negatively charged comb are attracted to each other. The force generated is sufficient to rotate the arrow in any direction.
Exercise!
Can you make an arrowhead out of aluminum foil?
Experience "Make an electroscope »
A device that allows you to detect even weak electrification of bodies.
In the laboratory, scientists measure the static charge using an electroscope (skpeo (Greek) - I observe). This device displays the relative amount of charge.
Materials (edit)
* Transparent plastic cup
* plasticine
* scissors
* two pieces of aluminum foil
* balloon
* fur
* metal paper clip
Sequencing
Make a small hole with the paperclip wire diameter in the center of the bottom of the glass. Cut out 0.5 x 4 cm pieces of aluminum foil. Unfold the paperclip and shape it into a hook. Hook the leaves. Insert the fully bent upper part of the paper clip into the hole in the bottom of the glass and secure with a piece of plasticine. The leaves should not touch the glass and should be clearly visible to you. Roll a small ball out of a piece of foil. Place the ball on the point of a paper clip sticking out of the glass. Put the glass on the table. Charge the balloon by rubbing it with a piece of wool or fur. Slowly bring the balloon to the foil balloon. What will happen to the leaves in the electroscope? Take away the balloon. How will the leaves react to this?
Explanation When you bring a balloon near an electroscope, it induces a charge. The balloon's negative charge repels the electrons in the aluminum foil balloon. These electrons flow down the paper clip to the leaves. Each leaf takes on a negative charge. Since the charges of the same name are repelled, the leaves fly in different directions. Why is the electroscope charged with a smaller charge, if we touch it with one point of an electrified ebony stick, and becomes infected with a large charge, if we run it over the ball with an ebony stick?
Experience "Magic Wand"
" Come to me. Listen to me. I command you. Turn around. " Do you dream of a magic wand? What do you want her to be able to do? Maybe use it to control the movement of various objects? If so, do you have a chance to get such a magic wand? Can all sticks be magic?
Materials (edit)
· table tennis ball
· plastic handle
· wool
Sequencing:
Place the table tennis ball on a flat surface so that it does not move. Rub the wool over the plastic handle. Then bring the pen close enough to the ball. What will happen? Try to move the handle so that the ball moves after it. Did you do it?
Explanation Since you rubbed the pen with wool, negative charges have shifted. These charges left the wool and accumulated on the handle. The pen has become negatively charged. When you brought the pen to the ball, its electric field affected the charges on the ball. Negative charges on the area of the ball closest to the handle are repelled from the handle and move inside the ball, which makes one side of the ball positively charged. This positively charged side of the ball and the negatively charged handle are attracted to each other. If inertia and friction are overcome, then the ball begins to move behind the handle.
Ghost Foot Experience
Materials:
* Nylon stocking
*plastic bag
* smooth wall
*balloon
* a piece of wool
Sequencing
Take a stocking in one hand, holding it by the upper end. With the other hand, rub the stocking several times with a plastic bag in one direction. Then remove the package. Make sure the stocking doesn't touch anything (not even you). What will happen to its shape? Can you explain what you see? Now bring the stocking up to the wall. What will happen to him? Is it like a balloon sticking to a wall if you rub the balloon with a piece of wool? Are there any differences? Charge the balloon again and see if it adheres well to wood, metal, or glass.
Explanation As the plastic bag moved along the stocking, it took away negative charges. This led to the stocking acquiring an overall positive charge. Since the positive charges were distributed throughout the stocking, they began to repel each other. This caused the stocking to "expand" and take the shape of a leg, which would be a template for making it. What happened when you put the stocking up against the wall? A positively charged stocking acts like a negatively charged ball and induces a charge of the opposite sign on the wall surface. Negative and positive charges are attracted, and the stocking sticks to the wall.
Experiment "Radio signal"
S… o… s... When the Titanic began to sink, its radio operator sent this signal for help. Each time the key is pressed to transmit messages using Morse code, the electrical circuit is temporarily closed. This short-circuit creates a spark, and signals are sent from the antenna of the sinking ship in the form of energy waves. These waves are received by antennas on other ships. From the antenna, the signal travels through wires to the radio. In a radio receiver, invisible waves are converted into audible sounds.
Experience will show you how you can use a spark to send a message using Morse code.
Materials and equipment
*carpet
* metal door handle
*radio
Sequencing
Turn on the radio. Tune it to a frequency that does not receive any signals. If you turn on the sound, the radio will only transmit atmospheric interference.
Walk in your shoes on the carpet. Go to the doorknob and touch it while listening to the radio. What do you hear?
Explanation A spark produces an electromagnetic wave, a special kind of energy. This wave propagates through space. The radio antenna can receive this type of energy. The signal is "captured" and carried over the wires to the radio circuit. In it, the signal is converted into sound, which is amplified and reproduced through a speaker.
An experience"Jumping grains"
Popcorn kernels are an excellent material for scientific experiments. Since they are very light, it does not take much force to move them. In addition, puffed grains carry electrical charges very well. Make sure of this and conduct an experiment.
Materials (edit)
* popcorn grains
* a piece of wool or fur
*balloon
Sequencing
Place a few beans in a balloon. Inflate the balloon. Rub the ball with a piece of wool or fur. If the fabric is not at hand, then rub the ball on your hair. Take the ball by the place where it is tied. Look at the grains inside the ball. Are they stationary or moving? Touch the ball with the fingers of your other hand. How will the grains behave? If nothing happens, recharge the balloon by rubbing it twice as long.
Explanation
Since you rubbed it with a ball of hair, it became negatively charged. This negative charge induces a positive charge on the side of the grains closest to the ball. This area of positive charge is attracted to the ball, causing the grains to adhere to the negatively charged surface of the ball.
When you touch the ball with your fingers. Things are changing. The negative charge flows from the balloon down your fingers. This creates positively charged areas on the ball. At the same time, the charges on the grains have not yet had time to move. As a result, the positively charged surfaces of the grains and the ball are repelled from each other, the grains jump to neighboring places.
Exercise!
Try touching the ball with a wooden stick. How will this change the behavior of the corn kernels in the ball?
An experience"Funny Bubbles"
Bubble is an example of a delicate balance of power. The surface tension of the water creates a force that tends to compress the thin film that forms the bubble. The soap in the water compensates for this force and makes the bubble resistant. As a result, a light sphere is formed, whose shape easily changes under the influence of static forces.
Materials (edit)
* soap solution
*mug
* cocktail tube
*balloon
Sequencing
Fill the mug 1/3 full with soapy water. Dip a tube into the solution. Blow slowly into the tube for a while. A lot of bubbles are formed, which fill the mug and fly over the edges.
Charge the balloon. Rubbing it on your hair. Bring the ball to the bubbles. What's happening? Describe how the shape of the bubbles changes. Is the force of attraction between the molecules in the film sufficient to expand the bubble to the diameter of the circle?
Explanation Like foam and puffed corn, bubbles react very well to static charges. Their light weight and high charging capacity make them an ideal subject for studying the effects of static attraction. When you bring a charged ball to the bubbles, the nearest electrons of the bubble react to it. These negatively charged particles move to the opposite side of the bubble. Therefore, one side of the bubble becomes positively charged. This side is attracted by a negatively charged ball. The attraction causes the bubble to expand and take the shape of an egg.
Exercise!
Will a bubble directly blown out of the tube also react to a charged balloon?
An experience"Combs"
Equipment
* hang two combs on a thread
Exercise!
How do you know which of these combs is electrified (nothing else can be used)?
Answer: Need one comb in hand? Thus, discharge it on yourself if it was charged. Then, holding the combs by the threads, bring them closer together and see how they behave now. If they interact, then the second comb is charged. If no interaction is observed, then the first comb has been charged.
Experiment - focus
Materials (edit)
* thin-walled glass
* steel needle
* ebony stick
*fur
Sequencing
There is a thin-walled glass on the table, almost filled to the top with water. Using tweezers, gently place the steel needle on the surface of the water - the needle floats. A "magic wand" is brought to the edge of the glass, and the needle starts to move, begins to move away. What's the matter?
Explanation The stick is taken pre-electrified by rubbing against the fur. Not only the needle is attracted to such a stick, but also water. Due to the attraction of water, its surface becomes inclined, the needle rolls down like a sled slide.
2. Any bodies interact with electrified bodies and become electrified themselves.
The teacher shows the following experiments.
Have you ever sat in a plastic chair with your bare hands on its armrests? If so, then you felt a "sticking" force acting on the tiny hairs on your hands. This force is caused by the charged plastic. As your body fidgets in your chair, electrons move onto the plastic, creating a "sticky" feeling.
Consider the cases of interaction of electrified bodies:
2.1with solids
Materials (edit)
* Wooden ruler 100 cm or wooden profile
* ebony or glass stick
* sharp support
* fur for ebony stick
Sequencing
1 We electrify the ebony stick by rubbing it against the fur, and bring it to a ruler balanced on a sharp support - the ruler will turn and be attracted to the stick.
Upon contact with an electrified stick, the ruler will push off from it. We used a 100cm ruler for the experiment.
2. To a large wooden board, horizontally suspended on two ropes, we bring an electrified ebony stick. We observe the turn of the board to the stick.We used a wooden platband 350 cm for the experiment.
2.2.1with liquids
Materials (edit)
* Fine jet of tap water
* ebony or glass stick
* fur for ebony stick
* glass rod newspaper
Sequencing
Let us bring an electrified ebonite or glass rod to the stream of water flowing out of the tap and find that the stream and water droplets are attracted to the rod and repel each other. Why is the jet deflected towards the stick?
Explanation When an electrified stick is brought to the stream, charges are induced in it, which interact with the charges of the stick. As a result, the jet deflects towards the stick. And the same charges are induced on the water droplets, so they are repelled.
2.2.2with liquids
Equipment
*tripod
* funnel with a rubber tube at the end and with a clip
* cotton wool for collecting water
* capacitor plates
* electrophore machine
Sequencing
Attach the funnel with a rubber tube at the end and with a clip to the tripod. Fill the funnel with water and get a thin stream that will flow between the condenser plates. Place a bathtub below to collect water. Connect the capacitor plates to the poles of the electrophoretic machine. While the machine is not running, there is no electric field. Water flows vertically. But as soon as the electrophoretic machine starts to work, the water jet is deflected. Moreover, the deflection of the jet alternates. It deviates to one plate, then to another. This alternation occurs at great speed. The stream of water "writes" between the plates of the capacitor, like an electron beam in a picture tube. Why is the jet deflected?
Experience is obtained even with a small charge of the capacitor plates. The distance between the plates in our experiment was 15 cm.
2.2.3with gases
Materials and equipment
* Glass vessel with a tube in the bottom
* copper shavings
*Nitric acid
* ebony stick
*fur
Sequencing
Pour some copper shavings into the vessel, fill them with nitric acid and close the vessel lid. A brown jet of nitric oxide ( N O2). Let us bring an electrified ebonite stick to it and find that the gas jet is attracted to the stick.
Output : This series of experiments proves that all bodies - gases, liquids, solids, light and heavy - interact with electrified bodies and become electrified themselves.
Used Books
1. Gorev LA Entertaining experiments in physics. A book for a teacher. - M .: Education, 1985
2. Methodical newspaper for teachers of physics, astronomy. Publishing house FIRST OF SEPTEMBER
3.Specio M. Di, Entertaining experiments: Electricity and magnetism, - M.: AST Astrel, 2004
Before the experiment, it is necessary to hold an ebonite stick through the flame of a gas burner in order to remove any random charges that may be on it; without this precaution, pieces of paper can be attracted to the stick without rubbing it against the fur.
Versorium is a device that is used to detect static electricity. Its name means "the thing that turns". The versorium got its name from the inventor who invented it about four hundred years ago, and although time has changed, the laws by which this device operates have been preserved.
Experience in a fume hood.
Fragment of the lesson
