Explain to the child what electric current is. Children's story about electricity

The level of curiosity of the baby usually rolls over in all respects, but the study of some phenomena can be extremely dangerous. Such knowledge includes the understanding of such a harmless thing as an electric current.

How to explain to a little why-do-it-yourselfer what it is and how his research of the world around him can end?

What is electric current: options for explaining to a child

Explanation options depend on the imagination of the parent and the meticulousness of the child. The most elementary way is to tell the kid that a strict Uncle Tok lives in all the sockets and wires, who really doesn’t like it when little children bother him, and can hurt them.

Parents who want not only to forbid the baby to climb where they don’t need to, but also to explain why it’s impossible to do this, can tell you that there are many small balls - electrons in all wires, sockets and electrical appliances. While we do not use electricity, the balls jump in place. But as soon as we turn on the light, TV, iron, the balls start to run fast. And if they come across a child's hand or a mother's finger on the way, the balls do not like it. They continue to run forward, pierce the handle and fingers, and it hurts a lot. Instead of balls, you can use the analogy with bees, which can sting painfully. True, not every kid will understand why bees are bad, because. most likely did not encounter their bites.

Also, cartoons will help parents, for example, “Advice from Aunt Owl” or “Fixies”, which tells about electric current and electrical appliances in a simple and accessible form.

Experiments with electric current for children

There is no need to say that any experiments related to electricity should be carried out under the vigilant supervision of adults. Here are a few experiments that will clearly demonstrate to the baby what an electric current is:

Take a 9V battery (so-called "pill") and have your child put it on the tip of the tongue. Explain to him that a slight burning sensation on the tongue is the little balls that ran, and they did not like that they were prevented from running. There are only a few balls in a small battery, so they beat quite a bit. And in sockets and wires there are much more such balls, so they will hit much more painfully.
A very visual demonstration is obtained using a 12 V light bulb. Turn it on in a normal electrical network. Naturally, it will burn out instantly, and it is very significant - with a sharp pop, and black spots will remain on the inner surface of the flask. Explain to the child that the balloons were very angry because they were forced to work in vain, so they ruined the light bulb.
Take a plastic stick, rub it on a piece of woolen cloth or hair, and then apply it to the pieces of paper. Explain to the child that the paper sticks to the stick because the balls jump out, grab the paper and do not let go. But if you touch the stick with your hand, the balls will get angry, because they do not have the strength to hold your hand, and they will painfully push it away.
Older children can demonstrate how electricity is made. To do this, take a flashlight that runs on a battery, or a small lamp. As a battery, use a lemon or a potato tuber, into which stick two wires - one copper, the second galvanized. Carefully connect the ends of the wire to the contacts of a flashlight or light bulb - they should light up. Particularly advanced parents can connect several tubers in series to get a higher voltage at the output. In a child, such a spectacle causes stormy delight.

Also, if you have the means at hand, design a simple dynamo for the baby and show him that the light is on only when you turn the knob, and as soon as you stop, the light goes out. At least a short respite and silence in the house after demonstrating such a miracle of technology is provided to you.

Tell the child, but don't make a mistake yourself

You should be aware that even after your explanations, the child will want to see for himself how painful the bees can sting from the outlet. Therefore, take all precautions related to electrical current. Here are the most simple and effective recommendations:

All sockets must be specially protected against interference by children.
If possible, do not use extension cords, children love to explore them.
Do not use faulty electrical appliances or sockets that are not securely fixed in sockets.
Try not to leave your baby alone in a room with electrical appliances turned on.
Punish the child for unauthorized inclusion of electrical appliances in the outlet.

Also be sure to teach your child that if smoke, cod, sparks and other signs of electrical wiring or electrical appliances malfunction, he should urgently call his parents for help and in no case go there himself. We wish you success!

Cognitive journey-acquaintance "Electricity and electrical appliances"

Scenario of a cognitive journey

Krivyakova Elena Yuryevna, teacher of the speech therapy group, MBDOU child development center - kindergarten No. 315, Chelyabinsk

Description:

Your attention is invited to the scenario of cognitive travel. Section "Child and the world around". The scenario of a cognitive journey is aimed at expanding and generalizing knowledge about electricity and electrical appliances, education of safe behavior in relation to electricity and electrical appliances, interest in objects around everyday life, use of acquired knowledge in gaming activities. The prepared material will be useful for teachers additional education, educators of speech therapy and general education groups.
Integration of educational areas:"Cognition", "Communication", "Security", "Socialization".
Types of children's activities: playful, cognitive, communicative, experimental.
Target: Development of interest in phenomena and objects in the surrounding world. Expanding knowledge of safe behavior.
Tasks
Educational:
1. Expand knowledge about electricity and electrical appliances.
2. Summarize children's knowledge about the benefits and dangers of electricity.
3. Fill up the children's dictionary with new concepts of "hydroelectric power station", "battery", "electric current".
Correction-developing:
4. Activate the speech and mental activity of children. To promote the ability to clearly and competently articulate their thoughts.
5. Automate sound pronunciation in children with onomatopoeia.
6. Develop visual and auditory attention, verbal-logical thinking, memory, creative imagination.
7. Develop children's social and communication skills in joint activities.
Educational:
8. Cultivate a friendly attitude towards peers through the ability to listen to a friend and accept the opinion of another.
9. To develop elementary skills of safe behavior in everyday life when handling electricity.
Expected Result: increasing interest in surrounding objects in everyday life and using the knowledge gained in everyday life.
Preliminary work: conversation "Journey into the past of an electric light bulb"; memorizing riddles and poems about electrical appliances; viewing illustrations depicting electrical appliances; selection of items powered by batteries, accumulators, batteries for the exhibition; children's stories from personal experience.
Equipment:
- a split picture depicting an electric light bulb;
- cards from the didactic game "Evolution of transport and things around us" using the example of a group of "lighting devices";
- candle;
- multimedia system;
- a toy set for conducting experiments in different branches of knowledge "Electric Siren" from a series of scientific toys "We study the world around us";
- exhibition of items powered by batteries, accumulators, batteries;
- easel;
- soft modules;
- models depicting safety rules when working with electrical appliances;
- emblems with the image of a light bulb according to the number of children.
Methods of training and education: artistic word (poems and riddles), demonstration material, use of TRIZ technology elements (techniques: “good - bad”, modeling), experimentation.
Terms and conditions: a spacious hall in which you can move freely; chairs according to the number of children; the table on which the exhibition is located; easel with inverted models of safe handling of electrical appliances.

Event progress:

Introductory word of the educator (stimulation for upcoming activities):
Dear Guys! I am glad to see you all healthy and cheerful. Today we will have an unusual journey, in which we will learn a lot of interesting things. And for starters...
Problem situation: pay attention to what is on the table? It looks like they are cut pieces of the picture. Take one part each, try to put together the big picture (children collect).
What happened? (electric lamp) .

Educator: Tell me, have people always used light bulbs for lighting? (children's answers).
Dive into the problem: I suggest you plunge into the past and trace how people illuminated their homes at different times.
Didactic game "Evolution of things around us"

Exercise: Before you are pictures of different lighting fixtures. Choose a picture that caught your attention and you liked it. And now, with their help, we will build a path from the past to the present. (Arrange the cards in chronological order, in accordance with the previous conversation: “Journey into the past of the light bulb”).
Educator: We have built a bridge from the past to the present. I will now take a candle, light it, and you follow me. (the child walking last collects pictures). We cross the "bridge" from the past to the "present".
Educator: Here we are in the present (the teacher invites the children to sit on chairs in front of the screen).
Riddle-poem:
I see an outlet up on the wall
And it becomes interesting to me

(Electricity)
Educator: Do you want to know how electricity comes to our house?
slide show

The teacher comments: This is a hydroelectric power plant. Under high pressure, water enters the turbine, where electricity is generated using a generator. It is supplied to special substations, and from them it then runs along wires to our homes, hospitals, factories and places where people cannot do without electricity.
Educator: Tell me, why do people still use electricity, besides lighting the room? (suggested answer of children: to use electrical appliances).
Game "Riddles-riddles"
Children take turns guessing riddles. After the children's answers, the correct answer appears on the multimedia screen.
1st child:
I see dust - I grumble,
I'll finish and swallow! (A vacuum cleaner)
Educator: What sounds can we hear when the vacuum cleaner is running? (J)
2nd child:
First load the laundry into it,
Pour the powder and plug it into the socket,
Do not forget to set the washing program
And then you can go to rest. (Washing machine)
Educator: What sounds do we hear when the washing machine is running? (RU).
3rd child:
Wrinkled dress? Nothing!
I'll smooth it out now
To work for me, not to get used to ...
Ready! Can be worn. (Iron)
Educator: What sounds can we hear while the iron is running? (PSh).
4th child:
Live there different products,
Cutlets, vegetables and fruits.
Sour cream, cream and sausages,
Sausages, milk and meat. (Fridge)
Educator: Well done, you and I not only solved all the riddles, but also remembered all the sounds that we hear when these electrical appliances are working.
I wonder what sounds we hear when the refrigerator is running? (answer DZ).
Guys, remember what electrical appliances we have not yet named, name them. (Children's answers are accompanied by a slide show). Did everyone remember?
Physical education minute (activation of attention and motor activity, restoration of working capacity).
Educator: Where is the refrigerator usually located in the apartment? (in the kitchen)
And we will imagine that we are in the kitchen (children perform movements in accordance with the text).
What's the noise in this kitchen?
We will fry cutlets.
We'll take a meat grinder
Let's quickly check the meat.
Beat together with a mixer
Everything we need for the cream.
To bake a cake soon
We turn on the electric stove.
Electrical appliances are amazing!
It would be hard for us to live without them.
Educator: Do you guys know that people have learned to tame electricity, and even hide it in special "houses": accumulators and batteries - they are called "batteries" (Show pictures on the slide).
Experiment (specially prepared table). Now we will conduct an experiment with you and check: is it true that the electrical system can operate on conventional batteries. And make sure that they really "live" electricity (Experiment with the "electric siren" set).

Educator: Guys, who knows where else people use these "houses" to store electricity: batteries, accumulators? (Answers: video camera, flashlights, control panel, camera). The teacher draws the attention of children to the exhibition, examine the exhibits.
Educator: Guys, think about it and tell me what benefits electricity brings to a person? (children's answers).
- Is there any harm? (children's answers).
Rules for safe handling when working with electrical appliances
Children sit down on soft modules opposite the easel.
Exercise: Using the models, we need to formulate the basic safety rules when working with electrical appliances. By showing the models, we formulate the rules.

Rule 1 Don't stick in electrical outlet foreign objects, especially metal!
Why? Because the current, like a bridge, will move over the subject on you and can greatly damage your health.

Rule 2 Do not touch bare wires with your hands!
Why? An electric current flows through a bare wire that is not protected by a winding, the impact of which can be fatal.

Rule 3 Do not touch the switched on devices with bare hands!
Why? You can get an electric shock as water is a conductor electric current.

Rule 4 Do not leave the included electrical appliances unattended!
Why? Because the included electrical appliances can cause a fire. When leaving home, always check whether the lights are out, whether the TV, tape recorder, electric heater, iron and other electrical appliances are turned off.
caregiver reads a poem:
ELECTRICITY
I see a socket down on the wall
And it becomes interesting to me
What kind of mysterious beast is sitting there,
Our devices to work orders?
The animal's name is electric current.
It's very dangerous to play with him, my friend!
Keep your hands away from the current.
Do not rush to put your fingers in the socket!
If you try to joke with the current,
He gets angry and can kill.
Current - for electrical appliances, understand
Better never tease him!
Summing up the educational journey.
So our journey ended - acquaintance with electricity and electrical appliances. What did you like and remember especially in our trip? (children's answers). I wish you to remember the importance of electrical appliances in our lives and not to forget about the insidiousness of electricity. Remember the safety rules for using electrical appliances. And such a cheerful electric light bulb - an emblem will remind us of our journey.

The teacher distributes to the children an emblem depicting an electric light bulb.

Electricity is perhaps the most significant discovery in human history. A previously unknown force has always existed and a vivid example of this is lightning. Faced with this phenomenon, scientists wondered where electricity came from and what is it?

The study of electricity continued for almost 2,700 years. From the very moment when the ancient philosopher Thales of Miletus discovered the attraction of small objects by amber rubbed on a piece of wool. Today we know that electricity is transmitted by electrons - small "balls" running through wires.

Experiment: put small pieces of paper on the table, and then take a simple plastic pen and rub it vigorously on a piece of wool or hair. By bringing the pen close to the pieces of paper, they will simply begin to stick to it. This is the attraction that arose as a result of a static charge.

In the process of research, scientists wondered where electricity comes from, and found more and more new sources. In nature, atmospheric electricity is static. The tiny droplets of water that make up clouds rub against each other. As a result, the friction builds up a charge and eventually discharges into each other or into the ground in the form of lightning.

electrostatic machine

The principle of its operation is based on the same friction, and modern electrostatic machines are demonstrated in physics lessons. The first such machine appeared in 1663. Then scientists noticed that when glass is rubbed against silk, one charge arises, and when resin rubs against wool, another charge arises. Opposite charges were then called "glassy and resinous electricity". Today we know that these are positive (+) and negative (-) charges.

Accumulated these charges in Leyden jar. It was the first capacitor, which was a glass jar wrapped in foil and filled with salt water. Water accumulated one charge, and foil - the second. When the contacts approach, a spark jumps between them, representing a small model of lightning.

Today it is an ordinary battery - a source direct current. The electric current in a battery is produced by a chemical reaction. You can also get it at home. Dip a simple nail into a glass of vinegar, and copper wire next to it. That's all - the battery is ready. The first galvanic cell was created by the outstanding physicist Volt. He took the zinc and silver circles and, alternating them in turn, arranged them with pieces of paper soaked in salt water. However, the clue for Volt was the experiment of Professor of Medicine Galvani. The scientist, studying anatomy, hung the frog's foot on a copper hook, and when he touched it with a steel object, the foot twitched. It took more than 10 years to unravel the mystery of where electricity came from, but in the end, Volt determined that it arose in the process of the interaction of different metals.

Generator

The first generator was created in 1831 by the famous physicist Faraday. The principle is based on the relationship between electricity and magnetism. The scientist wound a wire around the coil and when he moved a magnet inside the coil, an electric current appeared in the winding. The same principle is preserved in modern dynamos. Such devices are installed on the front wheel of the bicycle and connected to the headlight. There is a coil in the body, and a permanent magnet rotates in the middle. Modern industrial generators operating in power plants are more complex. In them, the permanent magnet was replaced with an excitation coil, that is, an electromagnet, but otherwise the same principle discovered by Faraday works.

As already mentioned, electricity is transmitted by electrons. In order for the electrons to start moving along the wires, they need additional energy. In simple generators, they get this energy from magnetic field, but in solar panels - from light. Small particles of light - photons, fall on a special matrix, which, under the influence of light, begins to give up electrons and an electric current arises.

modern electricity

Today it is difficult to imagine the existence of mankind without electricity. In addition, with the growth of technological capacities, one of the topical issues is where to get electricity from. Therefore, many different power plants are being built and operated in the world. Apart from the sun, all the rest produce electricity with the help of generators, but these generators rotate due to various forces.

Principle of operation various kinds power plants:

hydroelectric power station - rotation occurs due to the passage of water flow through the turbine (blades);
wind farm - rotation occurs due to the wind spinning the propeller blades;
thermal power plant - fuel is burned, heating water and turning it into steam. In turn, pressurized steam passes through the turbine and rotates the blades, and the rotation is transferred to the generator;
nuclear power plant - the principle is the same as that of a thermal one, only the water is heated not by the combustion of fuel, but by a delayed nuclear reaction.

This is where electricity comes from in our house. True, on its way, fast-moving electrons pass many more different installations, power stations and substations, where voltage is converted, power is distributed, etc. It is easier to explain to children where electricity comes from, saying that it is an invisible force obtained from nature itself - the flow of rivers, puffs of wind, fire. At the same time, it is imperative to warn that electric current is dangerous and does not forgive pranks, so it is better to stay away from sockets.

Zero

In an ordinary socket there are 2 contacts - phase and zero. Where does zero come from in electricity if plus and minus are phase variables? Each generator in the power plant has 3 windings and each generates a separate phase. Phases are denoted by Latin letters A, B and C. The ends of all 3 windings are closed, and the second ends are phase sources. The closing point of the windings is zero. Thus, the current from any of the windings passing through the load returns to the zero point. Additionally, in the panel house, zero is grounded, and the circuit is called "deeply grounded neutral". At overhead power line the neutral wire is grounded on the supports. This is done so that in the event of a short circuit, the current reaches a maximum sufficient to trigger the shut-off automation. In addition, if a break occurs on the main neutral wire, the earth will work as a collector and no accident will occur.

In some industrial electrical installations, an isolated neutral is performed, as this is provided for by the operational features of the installation itself. In houses, zero must be grounded.

The physics of electricity is something that each of us has to face. In the article we will consider the basic concepts associated with it.

What is electricity? For an uninitiated person, it is associated with a flash of lightning or with the energy that feeds the TV and washing machine. He knows that electric trains use electrical energy. What else can he say? Power lines remind him of our dependence on electricity. Someone can give a few other examples.

However, many other, not so obvious, but everyday phenomena are connected with electricity. Physics introduces us to all of them. We begin to study electricity (tasks, definitions and formulas) at school. And we learn a lot of interesting things. It turns out that a beating heart, a running athlete, a sleeping baby, and a swimming fish all generate electrical energy.

Electrons and protons

Let's define the basic concepts. From the point of view of a scientist, the physics of electricity is associated with the movement of electrons and other charged particles in various substances. Therefore, the scientific understanding of the nature of the phenomenon of interest to us depends on the level of knowledge about atoms and their constituent subatomic particles. The tiny electron is the key to this understanding. The atoms of any substance contain one or more electrons that move in various orbits around the nucleus, just as the planets revolve around the sun. Usually the number of electrons in an atom is equal to the number of protons in the nucleus. However, protons, being much heavier than electrons, can be considered as if fixed in the center of the atom. This extremely simplified model of the atom is quite enough to explain the basics of such a phenomenon as the physics of electricity.

What else do you need to know? Electrons and protons have the same electrical charge (but different sign), so they are attracted to each other. The charge of a proton is positive and that of an electron is negative. An atom that has more or less electrons than usual is called an ion. If there are not enough of them in an atom, then it is called a positive ion. If it contains an excess of them, then it is called a negative ion.

When an electron leaves an atom, it acquires some positive charge. An electron, deprived of its opposite - a proton, either moves to another atom, or returns to the previous one.

Why do electrons leave atoms?

This is due to several reasons. The most general is that under the influence of a pulse of light or some external electron, an electron moving in an atom can be knocked out of its orbit. Heat makes the atoms vibrate faster. This means that electrons can fly out of their atom. In chemical reactions, they also move from atom to atom.

Muscles provide a good example of the relationship between chemical and electrical activity. Their fibers contract when exposed to an electrical signal from the nervous system. Electric current stimulates chemical reactions. They lead to muscle contraction. External electrical signals are often used to artificially stimulate muscle activity.

Conductivity

In some substances, electrons under the action of an external electric field move more freely than others. Such substances are said to have good conductivity. They are called conductors. These include most metals, heated gases, and some liquids. Air, rubber, oil, polyethylene and glass are poor conductors of electricity. They are called dielectrics and are used to insulate good conductors. Ideal insulators (absolutely non-conductive) do not exist. Under certain conditions, electrons can be removed from any atom. However, these conditions are usually so difficult to meet that, from a practical point of view, such substances can be considered non-conductive.

Getting acquainted with such a science as physics (section "Electricity"), we learn that there is a special group of substances. These are semiconductors. They behave partly as dielectrics and partly as conductors. These include, in particular: germanium, silicon, copper oxide. Due to its properties, the semiconductor finds many applications. For example, it can serve as an electric valve: like a bicycle tire valve, it allows charges to move in only one direction. Such devices are called rectifiers. They are used both in miniature radios and in large power plants to convert alternating current into permanent.

Heat is a chaotic form of movement of molecules or atoms, and temperature is a measure of the intensity of this movement (in most metals, with decreasing temperature, the movement of electrons becomes freer). This means that the resistance to the free movement of electrons decreases with decreasing temperature. In other words, the conductivity of metals increases.

Superconductivity

In some substances at very low temperatures the resistance to the flow of electrons disappears completely, and the electrons, having begun to move, continue it indefinitely. This phenomenon is called superconductivity. At a temperature of several degrees above absolute zero (-273 ° C), it is observed in metals such as tin, lead, aluminum and niobium.

Van de Graaff generators

The school curriculum includes various experiments with electricity. There are many types of generators, one of which we would like to talk about in more detail. The Van de Graaff generator is used to produce ultra-high voltages. If an object containing an excess of positive ions is placed inside a container, then electrons will appear on the inner surface of the latter, and the same number of positive ions will appear on the outer surface. If we now touch the inner surface with a charged object, then all the free electrons will pass to it. On the outside, positive charges will remain.

In a Van de Graaff generator, positive ions from a source are applied to a conveyor belt that runs inside a metal sphere. The tape is connected to the inner surface of the sphere with the help of a conductor in the form of a comb. The electrons flow down from the inner surface of the sphere. Positive ions appear on its outer side. The effect can be enhanced by using two generators.

Electricity

The school physics course also includes such a concept as electric current. What is it? Electric current is due to the movement of electric charges. When an electric lamp connected to a battery is turned on, current flows through a wire from one pole of the battery to the lamp, then through its hair, causing it to glow, and back through the second wire to the other pole of the battery. If the switch is turned, the circuit will open - the current will stop flowing, and the lamp will go out.

Electron movement

Current in most cases is an ordered movement of electrons in a metal that serves as a conductor. In all conductors and some other substances there is always some random movement going on, even if there is no current flowing. Electrons in matter can be relatively free or strongly bound. Good conductors have free electrons that can move around. But in poor conductors, or insulators, most of these particles are strongly enough connected with atoms, which prevents their movement.

Sometimes, naturally or artificially, a movement of electrons in a certain direction is created in a conductor. This flow is called electric current. It is measured in amperes (A). Ions (in gases or solutions) and “holes” (lack of electrons in some types of semiconductors) can also serve as current carriers. The latter behave like positively charged electric current carriers. Some force is needed to make electrons move in one direction or another. In nature its sources can be: exposure to sunlight, magnetic effects and chemical reactions.Some of them are used to generate electric current.Usually for this purpose are: a generator using magnetic effects, and an element (battery) whose action is caused chemical reactions. Both devices, creating electromotive force(EMF) cause electrons to move in one direction along the circuit. The EMF value is measured in volts (V). These are the basic units of measurement for electricity.

The magnitude of the EMF and the strength of the current are interconnected, like pressure and flow in a liquid. Water pipes are always filled with water at a certain pressure, but water only starts flowing when the tap is turned on.

Similarly, an electrical circuit can be connected to a source of emf, but current will not flow until a path has been created for the electrons to move. It can be, say, an electric lamp or a vacuum cleaner, the switch here plays the role of a tap that “releases” the current.

Relationship between current and voltage

As the voltage in the circuit increases, so does the current. Studying a physics course, we learn that electrical circuits consist of several different sections: usually a switch, conductors and a device that consumes electricity. All of them, connected together, create a resistance to electric current, which (assuming a constant temperature) for these components does not change with time, but is different for each of them. Therefore, if the same voltage is applied to a light bulb and to an iron, then the flow of electrons in each of the devices will be different, since their resistances are different. Consequently, the strength of the current flowing through a certain section of the circuit is determined not only by voltage, but also by the resistance of conductors and devices.

Ohm's law

The magnitude of electrical resistance is measured in ohms (Ohm) in a science such as physics. Electricity (formulas, definitions, experiments) is a vast topic. We will not derive complex formulas. For the first acquaintance with the topic, what has been said above is enough. However, one formula is still worth deriving. She is quite uncomplicated. For any conductor or system of conductors and devices, the relationship between voltage, current and resistance is given by the formula: voltage = current x resistance. This is the mathematical expression of Ohm's law, named after George Ohm (1787-1854), who was the first to establish the relationship of these three parameters.

The physics of electricity is a very interesting branch of science. We have considered only the basic concepts associated with it. You learned what electricity is, how it is formed. We hope you find this information useful.

Electricity for dummies. School for electrician

We offer a small material on the topic: "Electricity for beginners." It will give an initial idea of the terms and phenomena associated with the movement of electrons in metals.

Term Features

Electricity is the energy of small charged particles moving in conductors in a certain direction.

With direct current, there is no change in its magnitude, as well as the direction of movement for a certain period of time. If a galvanic cell (battery) is chosen as the current source, then the charge moves in an orderly manner: from the negative pole to the positive end. The process continues until it completely disappears.

Alternating current periodically changes the magnitude, as well as the direction of movement.

AC transmission scheme

Let's try to understand what a phase is in electricity. Everyone has heard this word, but not everyone understands its true meaning. We will not go into details and details, we will choose only the material that is needed home master. A three-phase network is a method of transmitting electric current, in which current flows through three different wires, and it returns through one. For example, in electrical circuit there are two wires.

On the first wire to the consumer, for example, to the kettle, there is a current. The second wire is used for its return. When such a circuit is opened, there will be no passage of an electric charge inside the conductor. This diagram describes a single-phase circuit. What is a phase in electricity? A phase is a wire through which an electric current flows. Zero is the wire through which the return is made. AT three-phase circuit there are three phase wires at once.

The electrical panel in the apartment is necessary for the distribution of electric current to all rooms. Three-phase networks are considered economically feasible, since they do not require two neutral wires. When approaching the consumer, the current is divided into three phases, each with zero. The earthing switch, which is used in a single-phase network, does not carry a working load. He is a fuse.

For example, when there is short circuit there is a risk of electric shock, fire. To prevent such a situation, the current value should not exceed a safe level, the excess goes to the ground.

The manual "School for an electrician" will help novice craftsmen to cope with some breakdowns of household appliances. For example, if there are problems with the operation of the electric motor of the washing machine, the current will fall on the outer metal case.

In the absence of grounding, the charge will be distributed throughout the machine. When you touch it with your hands, a person will act as a ground electrode, having received an electric shock. If there is a ground wire, this situation will not occur.

Features of electrical engineering

The manual "Electricity for Dummies" is popular with those who are far from physics, but plan to use this science for practical purposes.

The beginning of the nineteenth century is considered the date of the appearance of electrical engineering. It was at this time that the first current source was created. The discoveries made in the field of magnetism and electricity have managed to enrich science with new concepts and facts of great practical importance.

The "School for an Electrician" manual assumes familiarity with the basic terms related to electricity.

Many collections of physics contain complex electrical circuits, as well as a variety of obscure terms. In order for beginners to understand all the intricacies of this section of physics, a special manual “Electricity for Dummies” was developed. An excursion into the world of the electron must begin with a consideration of theoretical laws and concepts. illustrative examples, historical facts used in Electricity for Dummies will help beginner electricians learn. To check progress, you can use tasks, tests, exercises related to electricity.

If you understand that you do not have enough theoretical knowledge to independently cope with the connection of electrical wiring, refer to the manuals for "dummies".

Safety and practice

First you need to carefully study the section on safety. In this case, during work related to electricity, there will be no emergencies hazardous to health.

In order to put into practice the theoretical knowledge gained after self-study of the basics of electrical engineering, you can start with the old household appliances. Before starting repairs, be sure to read the instructions that came with the device. Do not forget that electricity is not to be trifled with.

Electric current is associated with the movement of electrons in conductors. If a substance is not capable of conducting current, it is called a dielectric (insulator).

For the movement of free electrons from one pole to another, a certain potential difference must exist between them.

The intensity of the current passing through a conductor is related to the number of electrons passing through the cross section of the conductor.

The current flow rate is affected by the material, length, cross-sectional area of the conductor. As the length of the wire increases, its resistance increases.

Conclusion

Electricity is an important and complex branch of physics. The manual "Electricity for Dummies" considers the main quantities that characterize the efficiency of electric motors. Voltage units are volts, current is measured in amperes.

From any source electrical energy there is a certain amount of power. It refers to the amount of electricity generated by the device in a certain period of time. Energy consumers (refrigerators, washing machines, kettles, irons) also have power, consuming electricity during operation. If you wish, you can carry out mathematical calculations, determine the approximate fee for each household appliance.

Electricity

Classical electrodynamics

Electricity Magnetism

Electrostatics Magnetostatics Electrodynamics Electric circuit Covariant formulation Famous scientists

Classification

If charged particles move inside macroscopic bodies relative to a particular medium, then such a current is called electric conduction current. If macroscopic charged bodies are moving (for example, charged raindrops), then this current is called convection.

There are direct and alternating electric currents, as well as all kinds of alternating current. In such terms, the word "electric" is often omitted.

D.C - current, the direction and magnitude of which do not change with time.

Alternating current is an electric current that changes with time. Alternating current is any current that is not direct.

Periodic current - electric current, the instantaneous values of which are repeated at regular intervals in an unchanged sequence.

Sinusoidal current - periodic electric current, which is a sinusoidal function of time. Among the alternating currents, the main one is the current, the value of which varies according to a sinusoidal law. In this case, the potential of each end of the conductor changes with respect to the potential of the other end of the conductor alternately from positive to negative and vice versa, while passing through all intermediate potentials (including the zero potential). As a result, a current arises that continuously changes direction: when moving in one direction, it increases, reaching a maximum, called the amplitude value, then decreases, at some point becomes zero, then increases again, but in the other direction and also reaches the maximum value , falls off to then pass through zero again, after which the cycle of all changes resumes.

Quasi-stationary current - “a relatively slowly changing alternating current, for the instantaneous values of which the laws of direct currents are satisfied with sufficient accuracy” (TSB). These laws are Ohm's law, Kirchhoff's rules and others. Quasi-stationary current, as well as direct current, has the same current strength in all sections of an unbranched circuit. When calculating quasi-stationary current circuits due to the emerging e. d.s. capacitance and inductance inductions are taken into account as lumped parameters. Quasi-stationary are ordinary industrial currents, except for currents in long-distance transmission lines, in which the condition of quasi-stationarity along the line is not satisfied.

Current high frequency - alternating current, (starting from a frequency of approximately tens of kHz), for which such phenomena as the radiation of electromagnetic waves and the skin effect become significant. In addition, if the wavelength of the AC radiation becomes comparable to the dimensions of the elements of the electrical circuit, then the condition of quasi-stationarity is violated, which requires special approaches to the calculation and design of such circuits. (see long line).

Ripple current is a periodic electric current, the average value of which over the period is different from zero.

Unidirectional current is an electric current that does not change its direction.

Eddy currents

Main article: Eddy currents

Eddy currents (Foucault currents) are “closed electric currents in a massive conductor that occur when the magnetic flux penetrating it changes,” therefore eddy currents are induction currents. The faster the magnetic flux changes, the stronger the eddy currents. Eddy currents do not flow along certain paths in the wires, but, closing in the conductor, form vortex-like contours.

The existence of eddy currents leads to the skin effect, that is, to the fact that the alternating electric current and magnetic flux propagate mainly in the surface layer of the conductor. Eddy current heating of conductors leads to energy losses, especially in the cores of AC coils. To reduce energy losses due to eddy currents, the alternating current magnetic circuits are divided into separate plates, isolated from each other and located perpendicular to the direction of eddy currents, which limits the possible contours of their paths and greatly reduces the magnitude of these currents. At very high frequencies, instead of ferromagnets, magnetodielectrics are used for magnetic circuits, in which, due to the very high resistance, eddy currents practically do not occur.

Characteristics

It is historically accepted that current direction coincides with the direction of movement of positive charges in the conductor. In this case, if the only current carriers are negatively charged particles (for example, electrons in a metal), then the direction of the current is opposite to the direction of movement of charged particles.

Drift velocity of electrons

The speed (drift) of the directional movement of particles in conductors caused by an external field depends on the material of the conductor, the mass and charge of the particles, the ambient temperature, the applied potential difference and is much less than the speed of light. For 1 second, the electrons in the conductor move due to the ordered movement by less than 0.1 mm - 20 times slower than the speed of the snail [ source not specified 257 days]. Despite this, the propagation speed of the actual electric current is equal to the speed of light (the propagation speed of the electromagnetic wave front). That is, the place where the electrons change their speed of movement after a change in voltage moves with the speed of propagation electromagnetic oscillations.

Strength and current density

Main article: Current strength

Electric current has quantitative characteristics: scalar - current strength, and vector - current density.

Current strength - physical quantity, equal to the ratio of the amount of charge Δ Q (\displaystyle \Delta Q) , which has passed for some time Δ t (\displaystyle \Delta t) through the cross section of the conductor, to the value of this time interval.

I = ∆ Q ∆ t . (\displaystyle I=(\frac (\Delta Q)(\Delta t)).)

The current strength in the International System of Units (SI) is measured in amperes (Russian designation: A; international: A).

According to Ohm's law, the current I (\displaystyle I) in a circuit section is directly proportional to the voltage U (\displaystyle U) applied to this section of the circuit, and inversely proportional to its resistance R (\displaystyle R) :

I = U R . (\displaystyle I=(\frac (U)(R)).)

If the electric current is not constant in the circuit section, then the voltage and current strength are constantly changing, while for ordinary alternating current the average values of voltage and current strength are equal to zero. However, the average power of the heat released in this case is not equal to zero. Therefore, the following terms are used:

instantaneous voltage and current, that is, acting at a given moment in time.
peak voltage and current, that is, the maximum absolute values
effective (effective) voltage and current strength are determined by the thermal effect of the current, that is, they have the same values \u200b\u200bthat they have for direct current with the same thermal effect.

Current density is a vector, the absolute value of which is equal to the ratio of the current flowing through a certain section of the conductor, perpendicular to the direction of the current, to the area of this section, and the direction of the vector coincides with the direction of movement of positive charges that form the current.

According to Ohm's law in differential form, the current density in the medium j → (\displaystyle (\vec (j))) is proportional to the electric field strength E → (\displaystyle (\vec (E))) and the conductivity of the medium σ (\displaystyle \ \sigma ) :

J → = σ E → . (\displaystyle (\vec (j))=\sigma (\vec (E)).)

Power

Main article: Joule-Lenz law

In the presence of current in the conductor, work is done against the forces of resistance. The electrical resistance of any conductor consists of two components:

active resistance - resistance to heat generation;
reactance - "resistance due to the transfer of energy to an electric or magnetic field (and vice versa)" (TSB).

Generally, most of the work done by an electric current is released as heat. The power of heat loss is a value equal to the amount of heat released per unit time. According to the Joule-Lenz law, the power of heat loss in a conductor is proportional to the strength of the flowing current and the applied voltage:

P = I U = I 2 R = U 2 R (\displaystyle P=IU=I^(2)R=(\frac (U^(2))(R)))

Power is measured in watts.

In a continuous medium, the volumetric power loss p (\displaystyle p) is determined by the scalar product of the current density vector j → (\displaystyle (\vec (j))) and the electric field strength vector E → (\displaystyle (\vec (E))) in given point:

P = (j → E →) = σ E 2 = j 2 σ (\displaystyle p=\left((\vec (j))(\vec (E))\right)=\sigma E^(2)= (\frac (j^(2))(\sigma )))

Volumetric power is measured in watts per cubic meter.

Radiation resistance is caused by the formation of electromagnetic waves around the conductor. This resistance is in complex dependence on the shape and dimensions of the conductor, on the wavelength of the emitted wave. For a single rectilinear conductor, in which the current is of the same direction and strength everywhere, and the length of which L is much less than the length of the electromagnetic wave radiated by it λ (\displaystyle \lambda ) , the dependence of resistance on the wavelength and conductor is relatively simple:

R = 3200 (L λ) (\displaystyle R=3200\left((\frac (L)(\lambda ))\right))

The most used electric current with a standard frequency of 50 Hz corresponds to a wave with a length of about 6 thousand kilometers, which is why the radiation power is usually negligibly small compared to the heat loss power. However, as the frequency of the current increases, the length of the emitted wave decreases, and the radiation power increases accordingly. A conductor capable of radiating appreciable energy is called an antenna.

Frequency

Bias current

Main article: Displacement current (electrodynamics)

Sometimes, for convenience, the concept of displacement current is introduced. In Maxwell's equations, the displacement current is present on an equal footing with the current caused by the movement of charges. The intensity of the magnetic field depends on the total electric current, which is equal to the sum of the conduction current and the displacement current. By definition, the displacement current density j D → (\displaystyle (\vec (j_(D)))) is a vector quantity proportional to the rate of change of the electric field E → (\displaystyle (\vec (E))) in time:

J D → = ∂ E → ∂ t (\displaystyle (\vec (j_(D)))=(\frac (\partial (\vec (E)))(\partial t)))

The fact is that when the electric field changes, as well as when the current flows, a magnetic field is generated, which makes these two processes similar to each other. In addition, a change in the electric field is usually accompanied by energy transfer. For example, when charging and discharging a capacitor, despite the fact that there is no movement of charged particles between its plates, they speak of a displacement current flowing through it, carrying some energy and closing the electrical circuit in a peculiar way. The bias current I D (\displaystyle I_(D)) in a capacitor is given by:

I D = d Q d t = − C d U d t (\displaystyle I_(D)=(\frac ((\rm (d))Q)((\rm (d))t))=-C(\frac ( (\rm (d))U)((\rm (d))t))) ,

where Q (\displaystyle Q) is the charge on the capacitor plates, U (\displaystyle U) is the potential difference between the plates, C (\displaystyle C) is the capacitance of the capacitor.

Displacement current is not an electric current, because it is not related to the movement of an electric charge.

Main types of conductors

Unlike dielectrics, conductors contain free carriers of uncompensated charges, which, under the action of a force, usually a difference in electrical potentials, set in motion and create an electric current. The current-voltage characteristic (dependence of current strength on voltage) is the most important characteristic of a conductor. For metal conductors and electrolytes, it has the simplest form: the current strength is directly proportional to the voltage (Ohm's law).

Metals - here the current carriers are conduction electrons, which are usually considered as an electron gas, clearly showing the quantum properties of a degenerate gas.

Plasma is an ionized gas. Electric charge is carried by ions (positive and negative) and free electrons, which are formed under the influence of radiation (ultraviolet, X-ray and others) and (or) heating.

Electrolytes - "liquid or solid substances and systems in which ions are present in any noticeable concentration, causing the passage of an electric current." Ions are formed in the process of electrolytic dissociation. When heated, the resistance of electrolytes decreases due to an increase in the number of molecules decomposed into ions. As a result of the passage of current through the electrolyte, the ions approach the electrodes and are neutralized, settling on them. Faraday's laws of electrolysis determine the mass of the substance released on the electrodes.

There is also an electric current of electrons in a vacuum, which is used in cathode ray devices.

Electric currents in nature

Intracloud lightning over Toulouse, France. 2006

Atmospheric electricity is electricity that is contained in the air. For the first time, Benjamin Franklin showed the presence of electricity in the air and explained the cause of thunder and lightning. Subsequently, it was established that electricity accumulates in the condensation of vapors in the upper atmosphere, and the following laws were indicated, which atmospheric electricity follows:

at clear sky, as well as with cloudy weather, the electricity of the atmosphere is always positive, if at some distance from the observation point it does not rain, hail or snow;
the electricity voltage of the clouds becomes strong enough to release it from environment only when cloud vapors condense into raindrops, as evidenced by the fact that there are no lightning discharges without rain, snow or hail at the place of observation, excluding the return stroke of lightning;
atmospheric electricity increases with increasing humidity and reaches a maximum when rain, hail and snow fall;
the place where it rains is a reservoir of positive electricity, surrounded by a belt of negative electricity, which, in turn, is enclosed in a belt of positive. At the boundaries of these belts, the stress is zero. The movement of ions under the action of electric field forces forms a vertical conduction current in the atmosphere with an average density equal to about (2÷3)·10−12 A/m².

The total current flowing to the entire surface of the Earth is approximately 1800 A.

Lightning is a natural sparking electrical discharge. The electrical nature of the auroras was established. St. Elmo's fires are a natural corona electrical discharge.

Biocurrents - the movement of ions and electrons plays a very significant role in all life processes. The biopotential created in this case exists both at the intracellular level and in individual parts of the body and organs. The transmission of nerve impulses occurs with the help of electrochemical signals. Some animals ( electric ramps, electric eel) are capable of accumulating a potential of several hundred volts and use this for self-defense.

Application

When studying the electric current, many of its properties were discovered, which allowed him to find practical use in various areas of human activity, and even create new areas that would not be possible without the existence of electric current. After the electric current found practical application, and for the reason that the electric current can be obtained different ways, in the industrial sphere a new concept has arisen - the electric power industry.

Electric current is used as a carrier of signals of varying complexity and types in different areas (telephone, radio, control panel, door lock button, and so on).

In some cases, unwanted electric currents appear, such as stray currents or short circuit current.

The use of electric current as a carrier of energy

receiving mechanical energy in all kinds of electric motors,
obtaining thermal energy in heating devices, electric furnaces, during electric welding,
obtaining light energy in lighting and signaling devices,
excitation of electromagnetic oscillations of high frequency, ultrahigh frequency and radio waves,
receiving sound,
obtaining various substances by electrolysis, charging electric batteries. This is where electromagnetic energy is converted into chemical energy.
creating a magnetic field (in electromagnets).

The use of electric current in medicine

diagnostics - the biocurrents of healthy and diseased organs are different, while it is possible to determine the disease, its causes and prescribe treatment. The branch of physiology that studies electrical phenomena in the body is called electrophysiology.
- Electroencephalography is a method for studying the functional state of the brain.
- Electrocardiography is a technique for recording and studying electric fields during the work of the heart.
- Electrogastrography is a method for studying the motor activity of the stomach.
- Electromyography is a method for studying bioelectric potentials that occur in skeletal muscles.
Treatment and resuscitation: electrical stimulation of certain areas of the brain; treatment of Parkinson's disease and epilepsy, also for electrophoresis. Pacemaker that stimulates the heart muscle impulse current, used for bradycardia and other cardiac arrhythmias.

electrical safety

Main article: electrical safety

It includes legal, socio-economic, organizational and technical, sanitary and hygienic, medical and preventive, rehabilitation and other measures. Electrical safety rules are regulated by legal and technical documents, regulatory and technical framework. Knowledge of the basics of electrical safety is mandatory for personnel servicing electrical installations and electrical equipment. The human body is a conductor of electric current. Human resistance with dry and intact skin ranges from 3 to 100 kOhm.

The current passed through the human or animal body produces the following actions:

thermal (burns, heating and damage to blood vessels);
electrolytic (blood decomposition, violation of the physico-chemical composition);
biological (irritation and excitation of body tissues, convulsions)
mechanical (rupture of blood vessels under the action of steam pressure obtained by heating with blood flow)

The main factor determining the outcome of electric shock is the amount of current passing through the human body. According to safety measures, electric current is classified as follows:

safe a current is considered, the long passage of which through the human body does not harm him and does not cause any sensations, its value does not exceed 50 μA (alternating current 50 Hz) and 100 μA direct current;
minimally perceptible human alternating current is about 0.6-1.5 mA (alternating current 50 Hz) and 5-7 mA direct current;
threshold relentless called the minimum current of such a force at which a person is no longer able to tear his hands away from the current-carrying part by an effort of will. For alternating current, this is about 10-15 mA, for direct current - 50-80 mA;
fibrillation threshold is called an alternating current (50 Hz) of about 100 mA and 300 mA of direct current, the effect of which is longer than 0.5 s with a high probability of causing cardiac muscle fibrillation. This threshold is simultaneously considered conditionally lethal for humans.

In Russia, in accordance with the Rules technical operation electrical installations of consumers and the Rules for labor protection during the operation of electrical installations, 5 qualification groups for electrical safety have been established, depending on the qualifications and experience of the employee and the voltage of electrical installations.

How can I explain to a child what electricity is if I don’t understand it myself?

Svetlana52

You can very simply and clearly show what electricity is and how it is obtained, for this you need a flashlight that runs on batteries or a small lamp from a flashlight - the task is to get electricity, namely to make the light bulb light up. To do this, take a potato tuber and two copper and galvanized wires and stick it to the potato - use it as a battery - plus on the copper end, minus on the galvanized end - carefully attach it to a flashlight, or a light bulb - it should light up. To make the voltage higher, you can connect several potatoes in series. It is interesting to conduct such experiments with a child, and I think you will also enjoy it.

Rakitin Sergey

The simplest analogy is with water pipes through which hot water. The pump presses on the water, creating pressure - its analogue will be the voltage in the mains, the analogue of the current is the flow of water, the analogue of electrical resistance is the diameter of the pipe. Those. if the pipe is thin (large electrical resistance), then the trickle of water will also be thin (small current) to draw a bucket of water (get electrical power) a large pressure (high voltage) is needed through a thin pipe (therefore, high-voltage wires are relatively thin, low-voltage wires are thick, although the same power is transmitted through them).

Well, why is water hot - so that the child understands that electric current can burn no worse than boiling water, but if you put on a thick rubber glove (dielectric), then neither hot water nor current will burn you. Well, something like this (except perhaps one more thing - water molecules move in pipes, in electrical wires- electrons, charged particles of atoms of the metal from which these wires are made, in other materials, such as rubber, the electrons sit firmly inside the atoms, they cannot move, therefore such substances do not conduct current).

Inna interviewed

I just wanted to ask the question "What is electricity?" and got here. I know for sure that no one still knows how it happens that when a switch is turned on in one place, a light bulb instantly lights up in another (hundreds of kilometers away). What exactly is running through the wires? What is current? And how can it be explored if it beats, an infection))?

And the child can also show the mechanism of this process on potatoes, as advised in the Best Answer. But this number will not work with me!

Volck-79

Look how old he is. If 12-14 and he doesn't understand a belmez, then, excuse me, it's too late and hopeless. Well, if it’s five or eight years old (for example) - explain that all these things (holes, wires, all sorts of other beautiful objects) bite great, especially if you touch them, lick them, put your fingers in something, or vice versa poke.

Anfo-anfo

My daughter is 3 years old. At one time, I simply told her that it was dangerous, and now she does not climb into the sockets. And later I will explain that electricity is such an energy that gives light, from which a TV, computer and other equipment works. When she becomes a schoolgirl, she will study physics in more detail.

Ynkinamoy

you know many ways to explain to a child that it’s impossible, that it’s dangerous, I think that the child should be taught this, point to the rosette and say it’s impossible for you to go. If the child is still interested and he really wants to climb there, you need to install special if the child could not stick a finger or something metallic there, well, it’s best to use props and teach that it will hurt wow, that you can’t do it that it’s very bad that it will be bad for mom dad if he does it, bring to the child that you can’t do this, and use props. everything will be fine

Ksi Makarova

Now is the "age of the advanced Internet", ask any search engine a question, you can even with the wording "how to explain to a child what electricity is"))

Answering the tricky questions of my growing son, I managed to study a lot of topics in this way - it’s good for the child and useful for parents.

If you've ever looked at some electronic device and wondered, "How does it work?" and "Can I do it myself?" - or if your child has already grown out of the Znatok electronic construction set and is ready to move on, the Electronics for Children book is what you need, especially in such a rainy summer as this one. If you took your radio apart with rapture as a child, and now your son is asking how a computer works, this book is for you. The passage that we are publishing today will give children their first understanding of electricity and help them build their first device - a burglar alarm.

Before we start experiments with electricity - a little physics. How does electricity make a light bulb burn? A combination of four concepts is at work here. It:

Electrons
Voltage
Resistance

Everything that surrounds us is made up of atoms - particles so small that they can only be seen with a special type of microscope. But the atoms themselves are made up of even smaller particles—protons, neutrons, and electrons.

Protons and neutrons form the nucleus of an atom (its center), and electrons revolve around this nucleus, like planets around the Sun. Protons and electrons carry electrical charges, protons are positively charged and electrons are negatively charged.

That is why electrons are held in an atom: positive and negative charges attract each other like opposite poles of magnets.

Some substances have conductivity: if you act on them with energy (for example, stored in a battery), then the electrons in them begin to move from atom to atom!

By attaching a battery to a light bulb, you applied voltage to the light bulb filament. This voltage, measured in volts (V or V), pushes the electrons in one direction, causing them to move along the filament. The higher it is, the more electrons will move along the thread.

Imagine a thread in the form of a tube completely filled with balls. If a ball is pushed from one end of the pipe, another ball will immediately fall from its opposite end without any delay.

The more balls you push into one end of the pipe, the more they will fall out of the other. This is how electrons behave in the filament of a light bulb when voltage is applied to it.

Electric current is the flow of electrons through the filament of a light bulb. You may have heard the word current applied to a river: "This river has a strong current." This means that a lot of water flows through the river. Electric current is like this flow: when they say "strong current", it means that many electrons are flowing through the wire.

Current strength is measured in amperes (A). As the voltage in the circuit increases, so does the current. Just as water flows down a slope under the force of gravity, so current flows from the positive (+) battery terminal to the negative (-) terminal. In this case, the electrons themselves move in the opposite direction - from the negative terminal to the positive one. However, with regard to current, they always say that it flows from plus to minus.

Voltage causes electrons to move and thereby create an electric current, and resistance prevents this current. It's like playing with a garden hose: if you squeeze it, the resistance to the flow of water will increase and the flow will weaken, i.e., less water will flow. But if you open the faucet even more, the pressure will increase (it will be like increasing voltage), and the flow of water will increase, even if the hose remains compressed to the same degree. Resistance in electricity acts like squeezing a hose and is measured in ohms (ohms or Ω).

Now I will explain to you how electrons, current, voltage and resistance work together to make a light bulb glow.

The ends of the filament of the light bulb are connected to the details of its base: one - with the side surface of its body, the other - with the central contact. When you attach a light bulb to a battery, you create what is called an electrical circuit. A circuit is a path through which current can flow from the plus of the battery to the minus.

The voltage created by the battery causes the electrons to move along the circuit, of which the filament of the light bulb is a part. The thread has a resistance that limits the current in the circuit. When the electrons overcome the resistance of the filament, it becomes so hot that it begins to glow, i.e. emit light.

In order for a battery to make electrons move, the circuit between its terminals must not have breaks, that is, it must be closed.

For electricity to work, closed circuits are always needed. It is enough to open the circuit - to create at least one gap in it in any place, and the light bulb will immediately go out! Let's look at electrical circuits in more detail.

Let's continue looking at electricity by comparing it to the flow of water through pipes. Imagine a system of pipes in the form of a closed loop with a pump, which is completely filled with water. In one place, this system has a narrowing.

The pump plays the role of a battery that powers the circuit. The narrowing in the pipe reduces the flow of water. The same applies to resistance in an electrical circuit.

Now imagine that you could insert some kind of measuring device into this pipe system that would allow you to determine the amount of water flowing through it in one second. Note that here I'm only talking about how much water flows through one randomly selected spot in the pipe, not the total amount of water in the pipes. In the same way, we will talk about the strength of the current in the circuit: the strength of the current is the number of electrons flowing through a certain point in the circuit per second.

You use switches every time you turn the lights on or off. When the light in the room is on, the switch forms part of a closed circuit, since current flows through the lamp. But what happens when the switch is opened? The same thing happens as when the wire is disconnected in the circuit: the current through the lamp is interrupted and the lamp goes out, just as in the open circuit shown above.

You can find all sorts of switches around you, and they are very simple devices. They connect two wires to complete a circuit and disconnect them to open it. Even knowing only this, you can create good circuits, which is what we are going to do.

The switch can be made from a variety of things - even from a door. In this project, you'll turn a door into a giant switch to create a burglar alarm that will sound a warning every time someone tries to enter the room.

To create such an alarm, you need to attach several wires and a strip of aluminum foil to the door so that when the door is closed, the circuit is open and nothing happens, and when the door is opened, the circuit is closed, including the buzzer.

We will hang a bare (non-insulated) wire above the door, and glue a strip of foil on the upper edge of the door and connect these elements to different ends of the electrical circuit, which includes a buzzer. When the door is opened, the dangling bare wire will touch the foil and thereby complete the circuit, causing the buzzer to sound.

Materials and tools:

Buzzer. Buzzers are passive and active. Passive ones need an audio frequency input signal, while active ones need only voltage. For this project, you will need a 9-12V active buzzer (for example, KPIG2330E from KEPO. A buzzer sold at auto parts stores called "Audio Indicator (Repeater)" or "Audio Turn Signal" is also suitable. voltage 12 V).
Standard 9V battery to power the circuit.
Connector for connecting the battery to the circuit (block or terminal for "Krona" with wires).
Aluminium foil.
Bare wire. Flexible copper wire without insulation (do not confuse it with enameled winding wire, this is not good), an old guitar string or something like that will do.
Tape for fastening all elements. It can be electrical tape, adhesive tape, etc.
Nippers (side cutters) for wire and removal of insulation from wires.
Scissors (optional). They are great for cutting foil.

Step 1. Checking the buzzer. First of all, check if the buzzer is working. Press its red wire to the positive (+) terminal of the battery, and touch its black wire to the negative (-) terminal of the battery. The buzzer should make a loud sound. If you disconnect any of its wires from the battery, the sound should stop as the circuit is open.

Step 2 Preparing the Foil Cut a strip of foil about 2.5 cm wide and the entire width of the roll with scissors.

Step 3. Fixing the foil on the door. Secure both ends of the foil strip to the top edge of the door with two pieces of duct tape. This strip will serve as the contact for the battery and buzzer wires.

Step 4. Preparing the contact wire. Take a piece of bare wire about 25 cm long.

Step 5. Connecting the buzzer to the contact wire. Connect one end of the contact wire to the bare end of the black wire of the battery connector. To do this is simple: twist the bare ends of these wires together and wrap a piece of electrical tape around the twist.

After that, in the same way, connect the red wire of the battery connector to the red wire of the buzzer.

Step 6. Installing the buzzer and contact wire. Now install the buzzer and contact wire over the doorway. First, with adhesive tape, attach the contact wire to the door lintel so that when the door is closed, it hangs in front of the door, and when it opens, it lies on a strip of foil.

Now tape the buzzer over the lintel so that its black wire can touch the foil strip on the door. Tape the bare end of this wire to the foil.

Step 7. Connecting the power supply. Fix the battery over the door and connect the connector to it. Your signaling should now look something like this:

Step 8. Checking the alarm. Check the operation of the alarm. When opening the door, the bare contact wire should touch the foil on the door, thereby turning on the buzzer, which will make a loud sound. To make the test more reliable, ask someone else to open the door.

Step 9. If the alarm does not work. If the buzzer does not sound when the door is opened, try to adjust the position of the contact wire so that when the door is opened it exactly touches the foil. If the touch is correct, try replacing the battery. If this does not help, check the battery connector wire connections to the circuit wires and, if necessary, make them again.

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