Fundamentals of electrical engineering for beginners. Do-it-yourself electrician in your house. Basic electrical quantities and concepts

Electricity is used in many areas, it surrounds us almost everywhere. Electricity allows you to get safe lighting at home and at work, boil water, cook food, work on a computer and machine tools. However, you must be able to handle electricity, otherwise you can not only get injured, but also damage property. How to properly lay wiring, organize the supply of objects with electricity, is studied by such a science as electrical engineering.

The concept of electricity

All substances are made up of molecules, which in turn are made up of atoms. An atom has a nucleus and positively and negatively charged particles (protons and electrons) moving around it. When two materials are located next to each other, a potential difference arises between them (the atoms of one substance always have fewer electrons than the other), which leads to the appearance of an electric charge - the electrons begin to move from one material to another. This is how electricity is created. In other words, electricity is the energy resulting from the movement of negatively charged particles from one substance to another.

The speed of movement can be different. To move in the right direction and at the right speed, conductors are used. If the movement of electrons through the conductor is carried out in only one direction, such a current is called direct. If the direction of movement changes with a certain frequency, then the current will be variable. The most famous and simple source of direct current is a battery or car battery. Alternating current is actively used in households and in industry. Almost all devices and equipment work on it.

What does electrical engineering study

This science knows almost everything about electricity. It is necessary to study it for everyone who wants to get a diploma or qualification of an electrician. In most educational institutions, the course in which they study everything related to electricity is called "Theoretical Foundations of Electrical Engineering" or, for short, TOE.

This science was developed in the 19th century, when a direct current source was invented, and it became possible to build electrical circuits. Electrical engineering received further development in the process of new discoveries in the field of physics of electromagnetic radiation. In order to master science without problems at the present time, it is necessary to have knowledge not only in the field of physics, but also in chemistry and mathematics.

First of all, on the TOE course, the basics of electricity are studied, the definition of current is given, its properties, characteristics and directions of application are explored. Next, electromagnetic fields and the possibilities of their practical use are studied. The course ends, as a rule, with the study of devices that use electrical energy.

To deal with electricity, it is not necessary to enter a higher or secondary educational institution, it is enough to use a self-instruction manual or go through video tutorials “for dummies”. The knowledge gained is quite enough to deal with the wiring, replace a light bulb or hang a chandelier at home. But, if you plan to work professionally with electricity (for example, as an electrician or power engineer), then the appropriate education will be mandatory. It allows you to obtain a special permit to work with devices and devices powered by a current source.

Basic concepts of electrical engineering

Learning electricity for beginners, the main thing– deal with three key terms:

• Current strength;
• Voltage;
• Resistance.

The current strength is understood as the amount of electric charge flowing through a conductor with a certain cross section per unit of time. In other words, the number of electrons that have moved from one end of a conductor to the other in some time. The current strength is the most dangerous for human life and health. If you take a bare wire (and a person is also a conductor), then the electrons will pass through it. The more they pass, the more damage there will be, because in the course of their movement they release heat and start various chemical reactions.

However, in order for the current to flow through the conductors, there must be a voltage or potential difference between one and the other end of the conductor. Moreover, it must be constant so that the movement of electrons does not stop. To do this, the electrical circuit must be closed, and a current source must be placed at one end of the circuit, which ensures the constant movement of electrons in the circuit.

Resistance is a physical characteristic of a conductor, its ability to conduct electrons. The lower the resistance of the conductor, the more electrons pass through it per unit time, the higher the current strength. High resistance, on the contrary, reduces the current strength, but entails heating of the conductor (if the voltage is high enough), which can lead to a fire.

The selection of the optimal ratios between voltage, resistance and current strength in an electrical circuit is one of the main tasks of electrical engineering.

Electrical engineering and electromechanics

Electromechanics is a branch of electrical engineering. It studies the principles of functioning of devices and equipment that operate from an electric current source. Having studied the basics of electromechanics, you can learn how to repair various equipment or even design it.

As part of the lessons on electromechanics, as a rule, the rules for converting electrical energy into mechanical energy are studied (how an electric motor functions, the principles of operation of any machine, and so on). Inverse processes are also studied, in particular, the principles of operation of transformers and current generators.

Thus, without understanding how electrical circuits are composed, the principles of their functioning and other issues that electrical engineering studies, it is impossible to master electromechanics. On the other hand, electromechanics is a more complex discipline and is of an applied nature, since the results of its study are applied directly in the design and repair of machines, equipment and various electrical devices.

Safety and practice

When mastering a course in electrical engineering for beginners, it is necessary to pay special attention to safety issues, since non-compliance with certain rules can lead to tragic consequences.

The first rule to follow is to be sure to read the instructions. All electrical appliances in the instruction manual always have a section that deals with safety issues.

The second rule is to control the condition of the insulation of the conductors. All wires must be covered with special materials that do not conduct electricity (dielectrics). If the insulating layer is broken, first of all, it should be restored, otherwise damage to health is possible. In addition, for safety reasons, work with wires and electrical equipment should be done only in special clothing that does not conduct electricity (rubber gloves and dielectric boots).

The third rule is to use only special devices for diagnosing the parameters of the electrical network. In no case should you do this with your bare hands or try "on the tongue."

Note! Neglect of these elementary rules is the main cause of injuries and accidents in the work of electricians and electricians.

To get an initial understanding of electricity and the principles of operation of devices using it, it is recommended to take a special course or study the Electrical Engineering for Beginners manual. Such materials are designed specifically for those who are trying to master this science from scratch and gain the necessary skills to work with electrical equipment in everyday life.

The manual and video tutorials describe in detail how an electrical circuit works, what a phase is and what zero is, how resistance differs from voltage and current, and so on. Special attention is paid to safety precautions to avoid injury when working with electrical appliances.

Of course, studying courses or reading manuals will not allow you to become a professional electrician or electrician, but it will be quite possible to solve most household issues based on the results of mastering the material. For professional work, you already need to obtain a special permit and have a specialized education. Without this, it is prohibited to perform official duties by various instructions. If the enterprise allows a person without the necessary education to work with electrical equipment, and he gets injured, the manager will suffer a serious punishment, up to a criminal one.

Video

CONTENT:
INTRODUCTION


VARIETY OF WIRES
CURRENT PROPERTIES
TRANSFORMER
HEATING ELEMENTS


ELECTRICITY HAZARD
PROTECTION
AFTERWORD
POEM ABOUT ELECTRIC CURRENT
OTHER ARTICLES

INTRODUCTION

In one of the episodes "Civilization" I criticized the imperfection and cumbersomeness of education, because, as a rule, it is taught in a learned language, stuffed with incomprehensible terms, without visual examples and figurative comparisons. This point of view has not changed, but I am tired of being unfounded, and I will try to describe the principles of electricity in a simple and understandable language.

I am convinced that all difficult sciences, especially those describing phenomena that a person cannot comprehend with his five senses (sight, hearing, smell, taste, touch), for example, quantum mechanics, chemistry, biology, electronics, should be taught in the form of comparisons and examples. And even better - to create colorful educational cartoons about invisible processes inside matter. Now I will make electrically-technically literate people out of you in half an hour. And so, I begin the description of the principles and laws of electricity with the help of figurative comparisons ...

VOLTAGE, RESISTANCE, CURRENT

You can turn the wheel of a water mill with a thick stream with low pressure or a thin stream with high pressure. The pressure is the voltage (measured in VOLTS), the thickness of the jet is the current (measured in AMPERS), and the total force hitting the wheel blades is the power (measured in WATTs). The water wheel is figuratively comparable to an electric motor. That is, there can be high voltage and low current or low voltage and high current, and the power in both cases is the same.

The voltage in the network (socket) is stable (220 Volts), and the current is always different and depends on what we turn on, or rather on the resistance that the electrical appliance has. Current = voltage divided by resistance, or power divided by voltage. For example, it is written on the kettle - power (Power) 2.2 kW, which means 2200 W (W) - Watt, divided by the voltage (Voltage) 220 V (V) - Volt, we get 10 A (Amperes) - the current that flows when the kettle is working. Now we divide the voltage (220 Volts) by the operating current (10 Amperes), we get the resistance of the kettle - 22 Ohm (Ohm).

By analogy with water, resistance is like a pipe filled with a porous substance. To force water through this cavernous tube, a certain pressure (voltage) is needed, and the amount of fluid (current) will depend on two factors: this pressure, and how passable the tube is (its resistance). Such a comparison is suitable for heating and lighting devices, and is called ACTIVE resistance, and the resistance of electric coils. motors, transformers and el. magnets work differently (more on that later).

FUSES, AUTOMATICS, THERMOREGLATORS

If there is no resistance, then the current tends to increase to infinity and melts the wire - this is called a short circuit (short circuit). To protect against this email. fuses or circuit breakers (machines) are installed in the wiring. The principle of operation of the fuse (fusible insert) is extremely simple, this is a deliberately thin place in the email. chains, and where it is thin, it breaks there. A thin copper wire is inserted into the ceramic heat-resistant cylinder. The thickness (section) of the wire is much thinner than el. wiring. When the current exceeds the allowable limit, the wire burns out and "saves" the wires. In operating mode, the wire can become very hot, so sand is poured inside the fuse to cool it.

But more often, not fuses, but circuit breakers (automatic switches) are used to protect electrical wiring. The machines have two protection functions. One is triggered when too many electrical appliances are included in the network and the current exceeds the allowable limit. This is a bimetallic plate made of two layers of different metals, which expand differently when heated, one more, the other less. The entire operating current passes through this plate, and when it exceeds the limit, it heats up, bends (due to heterogeneity) and opens the contacts. The machine usually does not immediately turn back on, because the plate has not cooled down yet.

(Such plates are also widely used in thermal sensors that protect many household appliances from overheating and burnout. The only difference is that the plate is heated not by the transcendental current passing through it, but directly by the heating element of the device to which the sensor is tightly screwed. There are no contacts maintaining the set temperature.As if, without changing the strength of the fire of the burner, then put the kettle on it, then remove it.)

There is also a coil of thick copper wire inside the machine, through which the entire working current also passes. In the event of a short circuit, the strength of the magnetic field of the coil reaches a power that compresses the spring and draws in a movable steel rod (core) installed inside it, and it instantly turns off the machine. In operating mode, the coil force is not enough to compress the core spring. Thus, the machines provide protection against short circuits (short circuit), and from prolonged overload.

VARIETY OF WIRES

Electrical wires are either aluminum or copper. The maximum allowable current depends on their thickness (section in square millimeters). For example, 1 square millimeter of copper can withstand 10 amperes. Typical wire section standards: 1.5; 2.5; 4 "squares" - respectively: 15; 25; 40 Amperes - their allowable continuous current loads. Aluminum wires withstand current less than about one and a half times. The bulk of the wires have vinyl insulation, which melts when the wire overheats. The cables use insulation made of more refractory rubber. And there are wires with fluoroplastic (Teflon) insulation, which does not melt even in a fire. Such wires can withstand higher current loads than wires with PVC insulation. Wires for high voltage have thick insulation, for example on cars in the ignition system.

CURRENT PROPERTIES

Electricity requires a closed circuit. By analogy with a bicycle, where the leading star with pedals corresponds to the source of email. energy (generator or transformer), a star on the rear wheel - an electrical appliance that we plug into the network (heater, kettle, vacuum cleaner, TV, etc.). The upper segment of the chain, which transmits force from the leading to the rear star, is similar to the potential with voltage - phase, and the lower segment, which passively returns - to zero potential - zero. Therefore, there are two holes in the socket (PHASE and ZERO), as in a water heating system - an incoming pipe through which boiling water enters, and a return pipe - water that gives off heat in batteries (radiators) leaves through it.

Currents are of two types - direct and variable. Natural direct current that flows in one direction (like water in a heating system or a bicycle circuit) is produced only by chemical energy sources (batteries and accumulators). For more powerful consumers (for example, trams and trolleybuses), it is "rectified" from alternating current by means of semiconductor diode "bridges", which can be compared with a door lock latch - it is passed in one direction, locked in the other. But such a current turns out to be uneven, but pulsating, like a machine-gun burst or a jackhammer. To smooth the pulses, capacitors (capacitance) are placed. Their principle can be compared with a large full barrel, into which a "torn" and intermittent jet flows, and water flows steadily and evenly from its tap from below, and the larger the volume of the barrel, the better the jet. The capacitance of capacitors is measured in FARADs.

In all household networks (apartments, houses, office buildings and in production), the current is alternating, it is easier to generate it at power plants and transform (lower or increase). And most e. engines can only run on it. It flows back and forth, as if you take water into your mouth, insert a long tube (straw), immerse its other end in a full bucket, and alternately blow it out, then draw in water. Then the mouth will be similar to the potential with voltage - phase, and the full bucket - zero, which in itself is not active and not dangerous, but without it the movement of liquid (current) in the tube (wire) is impossible. Or, as when sawing a log with a hacksaw, where the hand will be the phase, the amplitude of movement will be voltage (V), the effort of the hand will be current (A), the energy will be frequency (Hz), and the log itself will be el. device (heater or electric motor), but instead of sawing - useful work. Sexual intercourse is also suitable for figurative comparison, a man is a “phase”, a woman is ZERO!, amplitude (length) is voltage, thickness is current, speed is frequency.

The number of oscillations is always the same, and always the same as that produced in the power plant and fed into the network. In Russian networks, the number of oscillations is 50 times per second, and is called the frequency of the alternating current (from the word often, not pure). The frequency unit is HERTZ (Hz), that is, our sockets are always 50 Hz. In some countries, the frequency in the networks is 100 Hertz. The frequency of rotation of most email depends on the frequency. engines. At 50 Hertz, the maximum speed is 3000 rpm. - on a three-phase power supply and 1500 rpm. - on single-phase (household). Alternating current is also necessary for the operation of transformers that step down high voltage (10,000 Volts) to normal household or industrial (220/380 Volts) in electrical substations. And also for small transformers in electronic equipment that lower 220 Volts to 50, 36, 24 Volts and below.

TRANSFORMER

The transformer consists of electrical iron (collected from a package of plates), on which a wire (varnished copper wire) is wound through an insulating coil. One winding (primary) is made of thin wire, but with a large number of turns. The other (secondary) is wound through a layer of insulation over the primary (or on an adjacent coil) of thick wire, but with a small number of turns. A high voltage comes to the ends of the primary winding, and an alternating magnetic field arises around the iron, which induces a current in the secondary winding. How many times there are fewer turns in it (secondary) - the voltage will be lower by the same amount, and how many times the wire is thicker - so much more current can be removed. As if, a barrel of water will be filled with a thin stream, but with a huge pressure, and from below a thick stream will flow out of a large tap, but with a moderate pressure. Similarly, transformers can be vice versa - step-up.

HEATING ELEMENTS

In heating elements, unlike transformer windings, the higher voltage will correspond not to the number of turns, but to the length of the nichrome wire from which the spirals and heating elements are made. For example, if you straighten the spiral of an electric stove at 220 volts, then the length of the wire will be approximately equal to 16-20 meters. That is, in order to wind a spiral at an operating voltage of 36 Volts, you need to divide 220 by 36, you get 6. This means that the length of the spiral wire at 36 Volts will be 6 times shorter, about 3 meters. If the spiral is intensively blown by a fan, then it can be 2 times shorter, because the air flow blows heat away from it and prevents it from burning out. And if, on the contrary, it is closed, then it is longer, otherwise it will burn out from a lack of heat transfer. You can, for example, turn on two heating elements of 220 volts of the same power in series at 380 volts (between two phases). And then each of them will be energized 380: 2 = 190 volts. That is, 30 volts less than the calculated voltage. In this mode, they will warm up a little (15%) weaker, but they will never burn out. It is the same with light bulbs, for example, you can connect 10 identical 24 Volt bulbs in series, and turn them on as a garland in a 220 Volt network.

HIGH VOLTAGE POWER LINES

It is advisable to transmit electricity over long distances (from a hydro or nuclear power plant to a city) only at high voltage (100,000 Volts) - so the thickness (section) of the wires on the supports of overhead power lines can be made minimal. If electricity were transmitted immediately under low voltage (as in sockets - 220 volts), then the wires of overhead lines would have to be made as thick as a log, and no aluminum reserves would be enough for this. In addition, high voltage more easily overcomes the resistance of the wire and the contacts of the connections (for aluminum and copper it is negligible, but it still runs decently over a length of tens of kilometers), like a motorcyclist rushing at breakneck speed, who easily flies through pits and ravines.

ELECTRIC MOTORS AND THREE-PHASE POWER

One of the main needs for alternating current is asynchronous el. engines, widely used because of their simplicity and reliability. Their rotors (the rotating part of the engine) do not have a winding and a collector, but are simply blanks made of electrical iron, in which the slots for the winding are filled with aluminum - there is nothing to break in this design. They rotate due to the alternating magnetic field created by the stator (the stationary part of the electric motor). To ensure the correct operation of motors of this type (and the vast majority of them) 3-phase power prevails everywhere. Phases, like three twin sisters, are no different. Between each of them and zero is a voltage of 220 Volts (V), the frequency of each is 50 Hertz (Hz). They differ only in time shift and "names" - A, B, C.

The graphical representation of the alternating current of one phase is depicted as a wavy line that wags a snake through a straight line - dividing these zigzags in half into equal parts. The upper waves reflect the movement of alternating current in one direction, the lower ones in the other direction. The height of the peaks (upper and lower) corresponds to the voltage (220 V), then the graph drops to zero - a straight line (the length of which represents time) and again reaches the peak (220 V) from the bottom side. The distance between the waves along a straight line expresses the frequency (50 Hz). The three phases on the chart are three wavy lines superimposed on each other, but with a lag, that is, when the wave of one reaches its peak, the other is already on the decline, and so on in turn - like a gymnastic hoop or a pan lid that has fallen to the floor. This effect is necessary to create a rotating magnetic field in three-phase asynchronous motors, which spins their moving part - the rotor. This is similar to bicycle pedals, on which the legs, like phases, press alternately, only here, as it were, three pedals are located relative to each other at an angle of 120 degrees (like the emblem of a Mercedes or a three-blade propeller of an airplane).

Three windings el. motor (each phase has its own) in the diagrams are depicted in the same way, like a propeller with three blades, one end connected at a common point, the other with the phases. The windings of three-phase transformers in substations (which lower high voltage to household voltage) are connected in the same way, and ZERO comes from a common winding connection point (transformer neutral). Generators producing el. energy have a similar scheme. In them, the mechanical rotation of the rotor (by means of a hydro or steam turbine) is converted into electricity in power plants (and in small mobile generators - by means of an internal combustion engine). The rotor, with its magnetic field, induces an electric current in three stator windings with a lag of 120 degrees around the circumference (like the Mercedes emblem). It turns out a three-phase alternating current with multi-temporal pulsation, which creates a rotating magnetic field. Electric motors, on the other hand, turn a three-phase current through a magnetic field into mechanical rotation. The winding wires have no resistance, but the current in the windings limits the magnetic field created by their turns around the iron, like gravity acting on a cyclist riding uphill and not allowing him to accelerate. The resistance of the magnetic field that limits the current is called inductive.

Due to the phases lagging behind each other and reaching the peak voltage at different instants, a potential difference is obtained between them. This is called line voltage and is 380 volts (V) in domestic applications. The linear (interphase) voltage is always greater than the phase voltage (between phase and zero) by 1.73 times. This coefficient (1.73) is widely used in the calculation formulas of three-phase systems. For example, the current of each phase el. motor = power in Watts (W) divided by line voltage (380 V) = total current in all three windings, which we also divide by a factor (1.73), we get the current in each phase.

Three-phase power supply creating a rotational effect for el. engines, due to the universal standard, it also provides power supply to domestic facilities (residential, office, retail, educational buildings) - where el. engines are not used. As a rule, 4-wire cables (3 phases and zero) come to common switchboards, and from there they diverge in pairs (1 phase and zero) to apartments, offices, and other premises. Due to the inequality of current loads in different rooms, the common zero is often overloaded, which comes to the email. shield. If it overheats and burns out, it turns out that, for example, neighboring apartments are connected in series (since they are connected by zeros on a common contact strip in the electrical panel) between two phases (380 Volts). And if one neighbor has powerful email. appliances (such as a kettle, heater, washing machine, water heater), while the other has low power (TV, computer, audio equipment), then the more powerful consumers of the first, due to the low resistance, will become a good conductor, and the second phase will appear in the sockets of the other neighbor instead of zero, and the voltage will be over 300 volts, which will immediately burn his equipment, including the refrigerator. Therefore, it is advisable to regularly check the reliability of the contact of zero coming from the supply cable with a common electrical distribution board. And if it heats up, then turn off the machines of all apartments, clean the soot and thoroughly tighten the contact of the common zero. With relatively equal loads on different phases, a larger proportion of reverse currents (through a common connection point of consumer zeros) will be mutually absorbed by adjacent phases. In three-phase el. motors, the phase currents are equal and completely go through neighboring phases, so they don’t need zero at all.

Single-phase el. motors operate from one phase and zero (for example, in domestic fans, washing machines, refrigerators, computers). In them, to create two poles - the winding is divided in half and located on two opposite coils on opposite sides of the rotor. And to create a torque, a second (starting) winding is needed, also wound on two opposite coils and with its magnetic field crosses the field of the first (working) winding at 90 degrees. The starting winding has a capacitor (capacitance) in the circuit, which shifts its impulses and, as it were, artificially emits a second phase, due to which a torque is created. Due to the need to divide the windings in half, the rotation speed of asynchronous single-phase el. engines cannot be more than 1500 rpm. In three-phase el. coil engines can be single, located in the stator through 120 degrees around the circumference, then the maximum rotation speed will be 3000 rpm. And if they are divided in half each, then you get 6 coils (two per phase), then the speed will be 2 times less - 1500 rpm, and the rotation force will be 2 times more. There may be 9 coils, and 12, respectively, 1000 and 750 rpm., With an increase in force as much as the number of revolutions per minute is less. The windings of single-phase motors can also be split more than in half with a similar decrease in speed and increase in force. That is, a low-speed engine is more difficult to hold on to the rotor shaft than a high-speed one.

There is another common type of email. engines - collector. Their rotors carry a winding and a contact collector, to which voltage comes through copper-graphite "brushes". It (the rotor winding) creates its own magnetic field. In contrast to the passively untwisted iron-aluminum "blank" asynchronous email. engine, the magnetic field of the rotor winding of the collector engine is actively repelled from the field of its stator. Such e. engines have a different principle of operation - like two poles of the same name of a magnet, the rotor (the rotating part of the electric motor) tends to push off the stator (the fixed part). And since the rotor shaft is firmly fixed by two bearings at the ends, the rotor is actively twisted out of "hopelessness". The effect is similar to a squirrel in a wheel, which the faster it runs, the faster the drum spins. Therefore, such e. motors have much higher and adjustable speed over a wide range than asynchronous ones. In addition, they, with the same power, are much more compact and lighter, do not depend on frequency (Hz) and operate on both alternating and direct current. They are used, as a rule, in mobile units: electric locomotives of trains, trams, trolleybuses, electric vehicles; as well as in all portable email. devices: electric drills, grinders, vacuum cleaners, hair dryers ... But they are significantly inferior in simplicity and reliability to asynchronous ones, which are used mainly on stationary electrical equipment.

ELECTRICITY HAZARD

Electric current can be converted into LIGHT (by passing through a filament, luminescent gas, LED crystals), HEAT (overcoming the resistance of nichrome wire with its inevitable heating, which is used in all heating elements), MECHANICAL WORK (through a magnetic field created by electric coils in electric motors and electric magnets, which respectively rotate and retract). However, e. current is fraught with a mortal danger to a living organism through which it can pass.

Some people say: "I was beaten by 220 volts." This is not true, because the damage is not caused by voltage, but by the current that passes through the body. Its value, at the same voltage, can differ tenfold for a number of reasons. Of great importance is the path of its passage. In order for a current to flow through the body, it is necessary to be part of an electrical circuit, that is, to become its conductor, and for this you must touch two different potentials at the same time (phase and zero - 220 V, or two opposite phases - 380 V). The most common dangerous current flows are from one hand to the other, or from the left hand to the feet, because this will lead through the heart, which can be stopped by a current of only one tenth of an ampere (100 milliamps). And if, for example, you touch the bare contacts of the socket with different fingers of one hand, the current will pass from finger to finger, and the body will not be affected (unless, of course, your feet are on a non-conductive floor).

The role of zero potential (ZERO) can be played by the earth - literally the soil surface itself (especially wet), or a metal or reinforced concrete structure that is dug into the ground or has a significant area of ​​\u200b\u200bcontact with it. It is not at all necessary to grab different wires with both hands, you can simply stand barefoot or in bad shoes on damp ground, concrete or metal floor, touch the bare wire with any part of the body. And instantly from this part, through the body to the legs, an insidious current will flow. Even if you go to the bushes out of necessity and inadvertently hit the bare phase, the current path will run through the (salty and much more conductive) urine stream, the reproductive system and legs. If there are dry shoes with thick soles on your feet or the floor itself is wooden, then there will be no ZERO and the current will not flow even if you cling to one bare PHASE live wire with your teeth (a vivid confirmation of this is birds sitting on bare wires).

The magnitude of the current largely depends on the area of ​​contact. For example, you can lightly touch two phases (380 V) with dry fingertips - it will hit, but not fatally. And you can grab onto two thick copper bars, to which only 50 volts are connected, with both wet hands - the contact area + dampness will provide conductivity ten times greater than in the first case, and the magnitude of the current will be fatal. (I have seen an electrician whose fingers were so hardened, dry, and calloused that he worked quietly under voltage, as if wearing gloves.) In addition, when a person touches voltage with his fingertips or the back of his hand, he reflexively withdraws. If you grab it like a handrail, then the tension causes contraction of the muscles of the hands and the person clings with a force that he has never been capable of, and no one can tear him off until the voltage is turned off. And the time of exposure (milliseconds or seconds) of electric current is also a very significant factor.

For example, in an electric chair, a person is put on a pre-shaved head (through a rag pad moistened with a special, well-conducting solution) tightly tightened wide metal hoop, to which one wire is connected - phase. The second potential is connected to the legs, on which (on the lower leg near the ankles) wide metal clamps are tightly tightened (again with wet special pads). For the forearms, the sentenced is securely fixed to the armrests of the chair. When the switch is turned on, a voltage of 2000 volts appears between the potentials of the head and legs! It is understood that with the received current strength and its path, loss of consciousness occurs instantly, and the rest of the "afterburning" of the body guarantees the death of all vital organs. Only, perhaps, the cooking procedure itself exposes the unfortunate person to such extreme stress that the electric shock itself becomes a deliverance. But do not be afraid - in our state there is no such execution yet ...

And so, the danger of hitting email. current depends on: voltage, current flow path, dry or wet (sweat due to salts has good conductivity) parts of the body, area of ​​​​contact with bare conductors, isolation of the feet from the ground (quality and dryness of shoes, soil dampness, floor material), current exposure time.

But to get under voltage, it is not necessary to grab onto a bare wire. It may happen that the insulation of the winding of the electrical unit is broken, and then the PHASE will be on its case (if it is metal). For example, there was such a case in a neighboring house - on a hot summer day, a man climbed onto an old iron refrigerator, sat on it with his bare, sweaty (and, accordingly, salty) thighs, and began to drill the ceiling with an electric drill, holding on to its metal part near the cartridge with his other hand ... Either he got into the armature (and it is usually welded to the general grounding contour of the building, which is equivalent to ZERO) of the concrete ceiling slab, or into his own electrical wiring ?? Just fell down dead, struck on the spot by a monstrous electric shock. The commission found a PHASE (220 volts) on the refrigerator case, which appeared on it due to a violation of the insulation of the compressor stator winding. Until you touch the body (with a lurking phase) and zero or "ground" (for example, an iron water pipe) at the same time, nothing will happen (chipboard and linoleum on the floor). But, as soon as the second potential (ZERO or another PHASE) is "found", the blow is inevitable.

GROUNDING is done to prevent such accidents. That is, through a special protective ground wire (yellow-green) to the metal cases of all el. devices is connected to ZERO potential. If the insulation is broken and the PHASE touches the case, then a short circuit (short circuit) with zero will instantly occur, as a result of which the machine will break the circuit and the phase will not go unnoticed. Therefore, electrical engineering switched to three-wire (phase - red or white, zero - blue, earth - yellow-green wires) wiring in single-phase power supply, and five-wire in three-phase (phases - red, white, brown). In the so-called euro-sockets, in addition to two sockets, grounding contacts (whiskers) were also added - a yellow-green wire is connected to them, and on euro-plugs, in addition to two pins, there are contacts from which the yellow-green (third) wire also goes to the body of the electrical appliance.

In order not to arrange a short circuit, RCDs (residual current device) have been widely used recently. The RCD compares the phase and zero currents (how much has entered and how much has left), and when a leak appears, that is, either the insulation is broken, and the winding of the motor, transformer or heater spiral "flashes" onto the case, or in general a person touches the current-carrying parts, then the "zero" current will be less than the phase one and the RCD will instantly turn off. Such a current is called DIFFERENTIAL, that is, third-party ("left") and should not exceed a lethal value - 100 milliamps (1 tenth of an ampere), and for household single-phase power this limit is usually 30 mA. Such devices are usually placed at the input (in series with automatic machines) of the wiring supplying damp dangerous rooms (for example, a bathroom) and protect against electric shock from hands - to the "ground" (floor, bath, pipes, water). From touching with both hands for the phase and the working zero (with a non-conductive floor), the RCD will not work.

The grounding (yellow-green wire) comes from one point with zero (from the common connection point of the three windings of a three-phase transformer, which is still connected to a large metal rod dug deep into the ground - GROUNDING at the electric substation supplying the microdistrict). In practice, this is the same zero, but "released" from work, just a "guard". So, in the absence of a ground wire in the wiring, you can use a neutral wire. Namely - in the euro-socket, put a jumper from the neutral wire to the grounding "whiskers", then if the insulation is broken and there is leakage to the case, the machine will work and turn off the potentially dangerous device.

And you can make the ground yourself - drive a couple of crowbars deep into the ground, spill it with a very salty solution and connect the ground wire. If you connect it to the common zero at the input (before the RCD), then it will reliably protect against the appearance of the second PHASE in the sockets (described above) and the combustion of household equipment. If it is not possible to reach it to a common zero, for example, in a private house, then the machine should be set to its own zero, as in a phase, otherwise, when the common zero burns out in the switchboard, the current of the neighbors will go through your zero to self-made grounding. And with the machine, support for neighbors will be provided only up to its limit and your zero will not suffer.

AFTERWORD

Well, it seems that I have described all the main common nuances of electricity that are not related to professional activities. Deeper details will require even longer text. How clear and intelligible it turned out is to be judged by those who are generally distant and incompetent in this topic (was :-).

A deep bow and blessed memory to the great European physicists who immortalized their names in units of measurement of electric current parameters: Alexandro Giuseppe Antonio Anastasio VOLTA - Italy (1745-1827); André Marie AMPER - France (1775-1836); Georg Simon OM - Germany (1787-1854); James WATT - Scotland (1736-1819); Heinrich Rudolf HERZ - Germany (1857- 1894); Michael FARADEY - England (1791-1867).

POEM ABOUT ELECTRIC CURRENT:

Wait, don't talk, let's talk a bit.
You wait, don't hurry, don't drive the horses.
You and I are alone in the apartment tonight.

electric current, electric current,
Tension similar to the Middle East,
From the time I saw the Bratsk hydroelectric power station,
I have taken an interest in you.

electric current, electric current,
They say you can be cruel sometimes.
Can take life from your insidious bite,
Well, let me, anyway, I'm not afraid of you!

electric current, electric current,
They say that you are a stream of electrons,
And chatting to the same idle people,
That you are controlled by the cathode and anode.

I don't know what "anode" and "cathode" means,
I have a lot of worries without it,
But while you're flowing, electric current
Boiling water will not dry up in my saucepan.

Igor Irteniev 1984

Now it is impossible to imagine life without electricity. This is not only lights and heaters, but all electronic equipment from the very first vacuum tubes to mobile phones and computers. Their work is described by a variety of, sometimes very complex formulas. But even the most complex laws of electrical engineering and electronics are based on the laws of electrical engineering, which in institutes, technical schools and colleges studies the subject "Theoretical Foundations of Electrical Engineering" (TOE).

Basic laws of electrical engineering

• Ohm's law
• Joule-Lenz law
• Kirchhoff's first law

Ohm's law- the study of TOE begins with this law, and not a single electrician can do without it. It states that current is directly proportional to voltage and inversely proportional to resistance. This means that the higher the voltage applied to the resistance, motor, capacitor or coil (with other conditions unchanged), the higher the current flowing through the circuit. Conversely, the higher the resistance, the lower the current.

Joule-Lenz law. Using this law, you can determine the amount of heat released on the heater, cable, electric motor power or other types of work performed by electric current. This law states that the amount of heat generated when an electric current flows through a conductor is directly proportional to the square of the current strength, the resistance of this conductor, and the time the current flows. With the help of this law, the actual power of electric motors is determined, and also on the basis of this law the electric meter works, according to which we pay for the consumed electricity.

Kirchhoff's first law. With its help, cables and circuit breakers are calculated when calculating power supply circuits. It states that the sum of the currents entering any node is equal to the sum of the currents leaving that node. In practice, one cable comes from the power source, and one or more goes out.

Kirchhoff's second law. It is used when connecting several loads in series or a load and a long cable. It is also applicable when connected not from a stationary power source, but from a battery. It states that in a closed circuit, the sum of all voltage drops and all EMFs is 0.

How to start learning electrical engineering

It is best to study electrical engineering in special courses or in educational institutions. In addition to the opportunity to communicate with teachers, you can use the material base of the educational institution for practical classes. The educational institution also issues a document that will be required when applying for a job.

If you decide to study electrical engineering on your own or you need additional material for classes, then there are many sites where you can study and download the necessary materials to your computer or phone.

Video lessons

There are many videos on the Internet that help you master the basics of electrical engineering. All videos can be watched online or downloaded using special programs.

Electrician video tutorials- a lot of materials that tell about various practical issues that a novice electrician may encounter, about programs that you have to work with and about equipment installed in residential premises.

Fundamentals of the theory of electrical engineering- here are video tutorials that clearly explain the basic laws of electrical engineering. The total duration of all lessons is about 3 hours.

zero and phase, wiring diagrams for light bulbs, switches, sockets. Types of tools for electrical installation;
1. Types of materials for electrical installation, electrical circuit assembly;
2. Switch connection and parallel connection;
3. Installation of an electric circuit with a two-gang switch. Model of power supply of the room;
4. Model of power supply of a room with a switch. Fundamentals of safety.

Books

The best adviser there has always been a book. Previously, it was necessary to borrow a book from the library, from friends or buy. Now on the Internet you can find and download a variety of books necessary for a novice or experienced electrician. Unlike video tutorials, where you can see how a particular action is performed, in a book you can keep it nearby while you work. The book may contain reference materials that will not fit in the video lesson (as in school - the teacher tells the lesson described in the textbook, and these forms of learning complement each other).

There are sites with a large amount of electrical literature on a variety of issues - from theory to reference materials. On all these sites, the desired book can be downloaded to a computer, and later read from any device.

For example,

mexalib- various kinds of literature, including electrical engineering

books for electrician- this site has a lot of tips for a beginner electrical engineer

electrical specialist- a site for novice electricians and professionals

Electrician's Library- many different books mainly for professionals

Online Tutorials

In addition, there are online textbooks on electrical engineering and electronics with an interactive table of contents on the Internet.

These are such as:

Beginner electrician course- Electrical Engineering Tutorial

Basic concepts

Electronics for beginners- basic course and basics of electronics

Safety

The main thing when performing electrical work is to comply with safety regulations. If improper operation can lead to equipment failure, then failure to follow safety precautions can lead to injury, disability or death.

Main Rules- this is not to touch live wires with bare hands, to work with a tool with insulated handles and, when the power is turned off, to hang out a poster "do not turn on, people are working." For a more detailed study of this issue, you need to take the book "Safety regulations for electrical installation and adjustment work."

Today, the transmission of electrical energy over a distance is always performed at an increased voltage, which is measured in tens and hundreds of kilovolts. All over the world, power plants of various types generate gigawatts of electricity. This electricity is distributed to towns and villages by means of wires, which we can see, for example, along highways and railways, where they are invariably fixed on high poles with long insulators. But why is the transmission always carried out at a high voltage? We will talk about this further...

Alternating current, in the traditional sense, is the current obtained due to the alternating, harmonically changing (sinusoidal) voltage. Alternating voltage is generated in a power plant and is always present in any wall outlet.It is also alternating current that is used to transmit electricity over long distances, since alternating voltage is easily increased with the help of a transformer, and thus electrical energy can be transmitted over a distance with minimal losses, and then lowered back ...

Metals are excellent conductors of electricity. They conduct electricity because they have free carriers of electric charge - free electrons. And if at the ends, for example, of a copper wire, a potential difference is created using a source of constant EMF, then an electric current will arise in such a conductor - the electrons will come into translational motion from the negative terminal of the EMF source to its positive terminal.Dielectrics, on the contrary, are not conductors of electric current, since there are no free carriers inside them ...

The first practical use of a magnet was in the form of a piece of magnetized steel floating on a cork in water or oil. In this case, one end of the magnet always points to the north, and the other - to the south. It was the first compass used by sailors.Just as long ago, several centuries before our era, people knew that a resinous substance - amber, if rubbed with wool, acquires for some time the ability to attract light objects: scraps of paper, pieces of thread, fluff. This phenomenon was called electrical. Later it was noticed that being electrified by friction ...

To answer the question “why doesn’t a dielectric conduct an electric current?” First, let’s remember what an electric current is, and also name the conditions that must be met for the occurrence and existence of an electric current. And after that, let's compare how conductors and dielectrics behave in relation to the search for an answer to this question.An electric current is an ordered, that is, directed, movement of charged particles under the influence of an electric field. Thus, firstly, for the existence of an electric current, the presence of free charged particles is necessary ...

The concept of energy is used in all sciences. At the same time, it is known that bodies with energy can produce work. The law of conservation of energy states that energy does not disappear and cannot be created from nothing, but appears in its various forms (for example, in the form of thermal, mechanical, light, electrical energy, etc.).One form of energy can be transformed into another, and at the same time, exact quantitative ratios of various types of energy are observed. Generally speaking, the transition from one form of energy to another is never complete...

Today there is not a single field of technology where electricity would not be used in one form or another. Meanwhile, the type of current that feeds them is connected with the requirements for electrical apparatus. And although alternating current is now very widespread throughout the world, there are nevertheless areas where you simply cannot do without direct current.The first sources of usable direct current were galvanic cells, which in principle gave chemically direct current., which is the flow of electrons ...

Electricity is now generally defined as "electric charges and their associated electromagnetic fields." The very existence of electric charges is revealed through their forceful effect on other charges. The space around any charge has special properties: electric forces act in it, which manifest themselves when other charges are introduced into this space. Such a space is a force electric field.While the charges are stationary, the space between them has the properties of an electric (electrostatic) field...

At present, it is already quite stable service market, including in the area household electrics.

Highly professional electricians, with undisguised enthusiasm, do their best to help the rest of our population, while receiving great satisfaction from the quality of work performed and modest remuneration. In turn, our population also gets great pleasure from a high-quality, fast and completely inexpensive solution to their problems.

On the other hand, there has always been a fairly wide category of citizens who fundamentally consider it an honor - personally resolve absolutely any domestic issues arising on the territory of their own place of residence. Such a position certainly deserves both approval and understanding.
Moreover, all these Replacements, transfers, installations- switches, sockets, automatic machines, counters, lamps, connecting kitchen stoves etc. - all these types of services most demanded by the population, from the point of view of a professional electrician, at all are not hard work.

And in truth, an ordinary citizen, without an electrical engineering education, but having sufficiently detailed instructions, can quite cope with its implementation himself, with his own hands.
Of course, doing such work for the first time, a novice electrician can spend much more time than an experienced professional. But it’s not at all a fact that from this it will be performed less efficiently, with attention to detail and without any haste.

Initially, this site was conceived as a collection of similar instructions on the most common problems in this area. But in the future, for people who have absolutely never encountered the solution of such issues, the course "young electrician" of 6 practical classes was added.

Features of installation of electrical sockets hidden and open wiring. Sockets for electric cooker. Do-it-yourself electric stove connection.

Switches.

Replacement, installation of electrical switches, hidden and open wiring.

Automata and RCDs.

The principle of operation of Residual Current Devices and circuit breakers. Classification of automatic switches.

Electric meters.

Instructions for self-installation and connection of a single-phase meter.

Wiring replacement.

Indoor electrical installation. Features of installation, depending on the material of the walls and the type of their finish. Electrical wiring in a wooden house.

Lamps.

Installation of wall lamps. Chandeliers. Installation of spotlights.

Contacts and connections.

Some types of conductor connections, most commonly found in "home" electrics.

Electrical engineering-basics of theory.

The concept of electrical resistance. Ohm's law. Kirchhoff's laws. Parallel and series connection.

Description of the most common wires and cables.

Illustrated instructions for working with a digital universal electrical measuring instrument.

About lamps - incandescent, fluorescent, LED.

About "money."

The profession of an electrician was definitely not considered prestigious until recently. But could it be called underpaid? Below, you can find the price list of the most common services from three years ago.

Electrical installation - prices.