Fundamentals of electrical engineering for beginners. Basic concepts of electricity

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) is 2.2 kW, which means 2200 W (W) - Watt, divided by voltage (Voltage) 220 V (V) - Volt, we get 10 A (Amps) - the current that flows at kettle work. 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 transcendent current passing through it, but directly by the heating element of the device, to which the sensor is tightly screwed. In devices with the desired temperature (irons, heaters, washing machines, water heaters) the shutdown limit is set by the thermo-regulator knob, inside of which there is also a bimetallic plate. teapot 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. Short circuit force magnetic field 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, man - "phase", woman - ZERO!, amplitude (length) - voltage, thickness - current, speed - 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

Transmit electricity over long distances (from hydro or nuclear power plant to the city) is advisable only under 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 more powerful consumers of the first, due to low resistance, will become a good conductor, and in sockets another neighbor, instead of zero, a second phase will appear, 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 the 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, contact area with bare conductors, isolation of feet from the ground (quality and dryness of shoes, soil dampness, floor material), time current impact.

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 common ground loop 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 (mustache) 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 case 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 coil is "flashed" onto the housing, or in general a person has touched the current-carrying parts, then the "zero" current will be less than the phase current 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 all the main common nuances of electricity that do not concern professional activity I described. 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

Content:

There are many concepts that you cannot see with your own eyes and touch with your hands. The most striking example is electrical engineering, which consists of complex circuits and obscure terminology. Therefore, many simply retreat before the difficulties of the upcoming study of this scientific and technical discipline.

To gain knowledge in this area will help the basics of electrical engineering for beginners, presented in an accessible language. Backed up historical facts and illustrative examples, they become fascinating and understandable even for those who first encountered unfamiliar concepts. Gradually moving from simple to complex, it is quite possible to study the presented materials and use them in practical activities.

Concepts and properties of electric current

Electrical laws and formulas are required not only for any calculations. They are also needed by those who in practice perform operations related to electricity. Knowing the basics of electrical engineering, you can logically determine the cause of a malfunction and eliminate it very quickly.

The essence of electric current is the movement of charged particles that carry an electric charge from one point to another. However, during random thermal motion of charged particles, following the example of free electrons in metals, charge transfer does not occur. The movement of an electric charge through the cross section of the conductor occurs only under the condition that ions or electrons participate in an ordered movement.

Electric current always flows in a certain direction. Its presence is evidenced by specific signs:

• Heating a conductor through which current flows.
• Change in the chemical composition of the conductor under the influence of current.
• Rendering a force impact on neighboring currents, magnetized bodies and neighboring currents.

Electric current can be direct and variable. In the first case, all its parameters remain unchanged, and in the second, the polarity changes periodically from positive to negative. In each half-cycle, the direction of the electron flow changes. The rate of such periodic changes is the frequency, measured in hertz.

Basic current quantities

When an electric current occurs in the circuit, there is a constant transfer of charge through the cross section of the conductor. The amount of charge transferred in a certain unit of time is called measured in amperes.

In order to create and maintain the movement of charged particles, the action of a force applied to them in a certain direction is necessary. In the event of termination of such an action, the flow of electric current also stops. Such a force is called the electric field, it is also known as. It is she who causes the potential difference or voltage at the ends of the conductor and gives impetus to the movement of charged particles. To measure this value, a special unit is used - volt. There is a certain relationship between the main quantities, reflected in Ohm's law, which will be discussed in detail.

The most important characteristic of a conductor, directly related to electric current, is resistance, measured in ohms. This value is a kind of resistance of the conductor to the flow of electric current in it. As a result of the resistance, the conductor is heated. With an increase in the length of the conductor and a decrease in its cross section, the resistance value increases. A value of 1 ohm occurs when the potential difference in the conductor is 1 V, and the current strength is 1 A.

Ohm's law

This law refers to the basic provisions and concepts of electrical engineering. It most accurately reflects the relationship between such quantities as current, voltage, resistance and. The definitions of these quantities have already been considered, now it is necessary to establish the degree of their interaction and influence on each other.

In order to calculate this or that value, you must use the following formulas:

1. Current strength: I \u003d U / R (amps).
2. Voltage: U = I x R (volts).
3. Resistance: R = U/I (ohm).

The dependence of these quantities, for a better understanding of the essence of the processes, is often compared with hydraulic characteristics. For example, at the bottom of a tank filled with water, a valve is installed with a pipe adjacent to it. When the valve is opened, water begins to flow, because there is a difference between the high pressure at the beginning of the pipe and the low pressure at the end. Exactly the same situation occurs at the ends of the conductor in the form of a potential difference - voltage, under the influence of which the electrons move along the conductor. Thus, by analogy, voltage is a kind of electrical pressure.

The current strength can be compared with the flow of water, that is, its amount flowing through the pipe section for a set period of time. With a decrease in the diameter of the pipe, the flow of water will also decrease due to an increase in resistance. This limited flow can be compared to the electrical resistance of a conductor, which keeps the flow of electrons within certain limits. The interaction of current, voltage and resistance is similar to hydraulic characteristics: with a change in one parameter, all the others change.

Energy and power in electrical engineering

In electrical engineering, there are also such concepts as energy And power associated with Ohm's law. Energy itself exists in mechanical, thermal, nuclear and electrical forms. According to the law of conservation of energy, it cannot be destroyed or created. It can only be transformed from one form to another. For example, audio systems convert electricity into sound and heat.

Any electrical appliance consumes a certain amount of energy over a set period of time. This value is individual for each device and represents the power, that is, the amount of energy that a particular device can consume. This parameter is calculated by the formula P \u003d I x U, the unit of measurement is . It means moving one volt through a resistance of one ohm.

Thus, the basics of electrical engineering for beginners will help at first to understand the basic concepts and terms. After that, it will be much easier to use the acquired knowledge in practice.

Electrics for Dummies: Basics of Electronics

Each of us, when he begins to get involved in something new, immediately rushes into the “abyss of passion” trying to complete or implement difficult projects. homemade. So it was with me when I became interested in electronics. But as it usually happens, the first failures diminished the fuse. However, I was not used to retreat and began to systematically (literally from the basics) comprehend the mysteries of the world of electronics. And so the "guide for beginner techies" was born.

Step 1: Voltage, Current, Resistance

These concepts are fundamental and without getting to know them, it would be pointless to continue learning the basics. Let's just remember that every material is made up of atoms, and every atom in turn has three types of particles. The electron is one of these particles and has a negative charge. Protons, on the other hand, have a positive charge. In conductive materials (silver, copper, gold, aluminum, etc.) there are many free electrons that move randomly. Voltage is the force that causes electrons to move in a certain direction. The flow of electrons that moves in one direction is called current. When electrons move through a conductor, they encounter some kind of friction. This friction is called drag. The resistance "squeezes" the free movement of electrons, thus reducing the amount of current.

A more scientific definition of current is the rate of change in the number of electrons in a certain direction. The unit of current is Ampere (I). In electronic circuits, the current flow is in the milliamp range (1 amp = 1000 milliamps). For example, the inherent current for an LED is 20mA.

The unit of voltage measurement is Volt (V). The battery is the source of voltage. Voltage 3V, 3.3V, 3.7V and 5V is the most common in electronic circuits and devices.

Voltage is the cause and current is the result.

The unit of resistance is Ohm (Ω).

Step 2: Power Supply

A battery is a source of voltage or a “correct” source of electricity. The battery produces electricity through an internal chemical reaction. It has two terminals on the outside. One is the positive terminal (+V) and the other is the negative terminal (-V), or ground. There are usually two types of power supplies.

• Batteries;
• Batteries.

Batteries are used once and then disposed of. Batteries can be used multiple times. Batteries come in many shapes and sizes, from miniature ones used to power hearing aids and wristwatches to room-sized batteries that provide backup power for telephone exchanges and computer centers. Depending on the internal composition, power supplies can be different types. A few of the most common types used in robotics and technical projects are:

Batteries 1.5 V

Batteries with this voltage can have different sizes. The most common sizes are AA and AAA. Capacity range from 500 to 3000 mAh.

3V lithium "coin"

All of these lithium cells are rated at 3V nominal (under load) and with an open circuit voltage of about 3.6 volts. The capacity can reach from 30 to 500mAh. Widely used in handheld devices due to their tiny size.

Nickel metal hydride (NiMG)

These batteries have a high energy density and can be recharged almost instantly. Another important feature is the price. Such batteries are cheap (compared to their size and capacity). This type of battery is often used in robotics homemade.

3.7V lithium ion and lithium polymer batteries

They have good discharge capacity, high energy density, excellent performance and small size. Lithium polymer battery widely used in robotics.

9 volt battery

The most common shape is a rectangular prism with rounded edges and terminals on top. The capacity is about 600 mAh.

Lead acid

Lead-acid batteries are the workhorse of the entire radio-electronics industry. They are incredibly cheap, rechargeable and easy to buy. Lead-acid batteries are used in mechanical engineering, UPS (uninterruptible power supplies), robotics and other systems where a large amount of energy is needed, and weight is not so important. The most common voltages are 2V, 6V, 12V and 24V.

Series-parallel connection of batteries

The power supply can be connected in series or in parallel. When connected in series, the voltage value increases, and when connected in parallel, the current value increases.

There are two important moments regarding batteries:

Capacity is a measure (usually in amp-hours) of charge stored in a battery and is determined by the mass of active material it contains. Capacity is the maximum amount of energy that can be extracted under certain specified conditions. However, the actual energy storage capacity of a battery may differ significantly from the nominal declared value, and battery capacity is highly dependent on age and temperature, charging or discharging modes.

Battery capacity is measured in watt hours (Wh), kilowatt hours (kWh), ampere hours (Ah), or milliamp hours (mAh). A watt-hour is the voltage (V) multiplied by the current (I) (we get the power - the unit of measurement is Watts (W)), which the battery can produce for a certain period of time (usually 1 hour). Since the voltage is fixed and depends on the type of battery (alkaline, lithium, lead-acid, etc.), often only Ah or mAh is marked on the outer shell (1000 mAh = 1Ah). For a longer operation of the electronic device, it is necessary to take batteries with a low leakage current. To determine battery life, divide the capacity by the actual load current. A circuit that draws 10 mA and is powered by a 9 volt battery will last about 50 hours: 500 mAh / 10 mA = 50 hours.

With many types of batteries, you can't "take" all the energy (in other words, the battery can't be fully discharged) without causing serious, and often irreparable, chemical damage. The depth of discharge (DOD) of a battery determines the proportion of current that can be drawn. For example, if DOD is defined by the manufacturer as 25%, then only 25% of the battery capacity can be used.

The charging/discharging rates affect the nominal capacity of the battery. If the power supply is being discharged very quickly (i.e., the discharge current is high), then the amount of energy that can be drawn from the battery is reduced and the capacity will be lower. On the other hand, if the battery is discharged very slowly (low current is used), then the capacity will be higher.

The temperature of the battery will also affect the capacity. With more high temperatures battery capacity is generally higher than at lower temperatures. However, intentionally raising the temperature is not effective way increase the capacity of the battery, as this also reduces the life of the power supply itself.

C-capacity: The charge and discharge currents of any battery are measured relative to its capacity. Most batteries, with the exception of lead acid, are rated at 1C. For example, a battery with a capacity of 1000mAh will deliver 1000mA for one hour if the level is 1C. The same battery, with a level of 0.5C, delivers 500mA for two hours. With level 2C, the same battery delivers 2000mA for 30 minutes. 1C is often referred to as the one-hour discharge; 0.5C is like a two hour clock and 0.1C is like a 10 hour clock.

Battery capacity is usually measured with an analyzer. Current analyzers display information as a percentage based on the nominal capacitance value. A new battery sometimes delivers more than 100% current. In such a case, the battery is simply conservatively rated and may last longer than specified by the manufacturer.

The charger can be selected in terms of battery capacity or C value. For example, a charger rated C/10 will fully charge the battery in 10 hours, a charger rated 4C would charge the battery in 15 minutes. Very fast charging rates (1 hour or less) usually require the charger to closely monitor battery parameters such as voltage limits and temperature to prevent overcharging and damage to the battery.

The voltage of the galvanic cell is determined chemical reactions that pass within it. For example, alkaline cells - 1.5 V, all lead acid- 2 V, and lithium - 3 V. Batteries can consist of several cells, so you rarely see a 2-volt lead-acid battery. They are usually wired together internally to provide 6V, 12V, or 24V. Keep in mind that the nominal voltage in a "1.5V" AA battery actually starts at 1.6V, then quickly drops to 1.5V, then slowly drifts down to 1.0 V, at which the battery is already considered 'discharged'.

How best to choose a battery for crafts?

As you already understood, in the public domain, you can find many types of batteries with different chemical composition Thus, it is not easy to choose which nutrition is the best for your specific project. If the project is very volatile ( large systems sound and motorized homemade) should choose a lead-acid battery. If you want to build a portable under the tree, which will consume a small current, then you should choose a lithium battery. For any portable project (light weight and moderate power), choose a lithium-ion battery. You can choose a cheaper nickel metal hydride (NIMH) battery, although they are heavier, but are not inferior to lithium-ion in other characteristics. If you would like to do a power intensive project then a Lithium Ion Alkaline (LiPo) battery would be the best option because it is small, light compared to other types of batteries, recharges very quickly and delivers high current.

Do you want your batteries to last a long time? Use a high-quality charger that has sensors to maintain the correct charge level and trickle charge. A cheap charger will kill your batteries.

Step 3: Resistors

A resistor is a very simple and most common element in circuits. It is used to control or limit the current in an electrical circuit.

Resistors are passive components that only consume power (and cannot produce it). Resistors are typically added to a circuit where they complement active components such as op amps, microcontrollers, and other integrated circuits. They are typically used to limit current, separate voltages and I/O lines.

The resistance of a resistor is measured in ohms. Large values can be matched with a kilo-, mega-, or giga prefix to make the values ​​easy to read. It is common to see resistors labeled kΩ and MΩ range (mΩ resistors are much rarer). For example, a 4,700Ω resistor is equivalent to a 4.7kΩ resistor, and a 5,600,000Ω resistor can be written as 5,600kΩ or (more commonly) 5.6MΩ.

There are thousands of different types of resistors and many companies that make them. If we take a rough gradation, then there are two types of resistors:

• with clearly defined characteristics;
• general purpose, whose characteristics can "walk" (the manufacturer himself indicates a possible deviation).

An example of general characteristics:

• temperature coefficient;
• voltage factor;
• Frequency range;
• Power;
• physical size.

According to their properties, resistors can be classified as:

Line resistor- a type of resistor whose resistance remains constant as the potential difference (voltage) that is applied to it increases (the resistance and current that passes through the resistor does not change with the applied voltage). The features of the current-voltage characteristic of such a resistor are a straight line.

non linear resistor It is a resistor whose resistance changes depending on the value of the applied voltage or the current flowing through it. This type has a non-linear current-voltage characteristic and does not strictly follow Ohm's law.

There are several types of non-linear resistors:

• Resistors NTC (Negative Temperature Coefficient) - their resistance decreases with increasing temperature.
• PEC (Positive Temperature Coefficient) resistors - their resistance increases with temperature.
• Resistors LZR (Light-dependent resistors) - their resistance changes with a change in the intensity of the light flux.
• VDR resistors (Volt dependent resistors) - their resistance drops critically when the voltage value exceeds a certain value.

Non-linear resistors are used in various projects. LZR is used as a sensor in various robotic projects.

In addition, resistors come with a constant and variable value:

Constant value resistors- types of resistors, the value of which is already set during production and cannot be changed during use.

Variable resistor or potentiometer - a type of resistor whose value can be changed during use. This type usually has a shaft that is rotated or moved by hand to change the resistance value within a fixed range, such as from. 0 kΩ to 100 kΩ.

Resistance Store:

This type of resistor consists of a "package" that contains two or more resistors. It has several terminals through which the resistance value can be selected.

The composition of the resistors are:

Carbon:

The core of such resistors is cast from carbon and a binder, creating the required resistance. The core has cup-shaped contacts holding a resistor rod on each side. The entire core is filled with a material (like Bakelite) in an insulated housing. The package has a porous structure, so carbon composite resistors are sensitive to the relative humidity of the environment.

These types of resistors usually produce noise in the circuit due to the electrons passing through the carbon particles, so these resistors are not used in "important" circuits, although they are cheaper.

Carbon deposition:

A resistor that is made by depositing a thin layer of carbon around a ceramic rod is called a carbon-deposited resistor. It is made by heating ceramic rods inside a methane bulb and depositing carbon around them. The value of the resistor is determined by the amount of carbon deposited around the ceramic rod.

Film Resistor:

The resistor is made by depositing the sprayed metal in vacuum on the ceramic base of the rod. These types of resistors are very reliable, have a high resistance, and also have a high temperature coefficient. Although they are more expensive compared to others, they are used in basic systems.

Wirewound Resistor:

A wirewound resistor is made by winding a metal wire around a ceramic core. The metal wire is an alloy of various metals selected according to the declared features and resistances of the required resistor. This type of resistor is highly stable and can handle high power, but is generally more bulky than other types of resistors.

Metal-ceramic:

These resistors are made by firing some metals mixed with ceramics on a ceramic substrate. The proportion of mixture in a mixed metal-ceramic resistor determines the resistance value. This type is very stable and also has a precisely measured resistance. They are mainly used for surface mounting on printed circuit boards.

Precision Resistors:

Resistors whose resistance value lies within tolerance, so they are very accurate (the nominal value is in a narrow range).

All resistors have a tolerance, which is given as a percentage. Tolerance tells us how close to nominal value resistance may change. For example, a 500Ω resistor that has a tolerance value of 10% could have a resistance between 550Ω or 450Ω. If the resistor has a tolerance of 1%, the resistance will only change by 1%. So a 500Ω resistor can range from 495Ω to 505Ω.

A precision resistor is a resistor that has a tolerance level of only 0.005%.

Fusible resistor:

A wire resistor designed to burn out easily when the rated power exceeds the limit threshold. So the fusible resistor has two functions. When the power is not exceeded, it serves as a current limiter. When the rated power is exceeded, it functions as a fuse, after a burnout, the circuit becomes open, which protects the components from short circuits.

Thermistors:

A heat-sensitive resistor whose resistance value changes with the operating temperature.

Thermistors display either positive temperature coefficient (PTC) or negative temperature coefficient (NTC).

How much resistance changes with changes in operating temperature depends on the size and design of the thermistor. It's always best to check the reference data to know all the thermistor specifications.

Photoresistors:

Resistors whose resistance varies depending on the light flux that falls on its surface. In a dark environment, the resistance of the photoresistor is very high, several M Ω. When intense light hits a surface, the resistance of the photoresistor drops significantly.

Thus, photoresistors are variable resistors, the resistance of which depends on the amount of light that falls on its surface.

Output and non-lead types of resistors:

Lead Resistors: This type of resistor was used in the earliest electronic circuits. The components were connected to the output terminals. Over time, printed circuit boards began to be used, in the mounting holes of which the leads of radioelements were soldered.

Surface Mount Resistors:

This type of resistor has been used more and more since the introduction of surface mount technology. Usually this type of resistor is created using thin film technology.

Step 4: Standard or Common Resistor Values

The naming convention has its origins going back to the beginning of the last century, when most resistors were carbon based with relatively poor manufacturing tolerances. The explanation is quite simple - using a 10% tolerance, you can reduce the number of produced resistors. It would be inefficient to manufacture 105 ohm resistors, since 105 is within the 10% tolerance range of a 100 ohm resistor. The next market category is 120 ohms because a 100 ohm resistor with 10% tolerance will have a range between 90 and 110 ohms. A 120 ohm resistor has a range between 110 and 130 ohms. By this logic, it is preferable to produce resistors with a 10% tolerance of 100, 120, 150, 180, 220, 270, 330 and so on (rounded accordingly). This is the E12 series shown below.

Tolerance 20% E6,

Tolerance 10% E12,

Tolerance 5% E24 (and usually 2% tolerance)

Tolerance 2% E48,

E96 1% tolerance,

E192 0.5, 0.25, 0.1% and higher tolerances.

Standard resistor values:

E6 series: (20% tolerance) 10, 15, 22, 33, 47, 68

E12 series: (10% tolerance) 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82

E24 series: (5% tolerance) 10, 11, 12, 13, 15, 16, 18, 20, 22, 24, 27, 30, 33, 36, 39, 43, 47, 51, 56, 62, 68, 75, 82, 91

E48 series: (2% tolerance) 100, 105, 110, 115, 121, 127, 133, 140, 147, 154, 162, 169, 178, 187, 196, 205, 215, 226, 237, 249, 261, 274, 287, 301, 316, 332, 348, 365, 383, 402, 422, 442, 464, 487, 511, 536, 562, 590, 619, 649, 681, 715, 750, 787, 825, 8 66, 909, 953

E96 series: (1% tolerance) 100, 102, 105, 107, 110, 113, 115, 118, 121, 124, 127, 130, 133, 137, 140, 143, 147, 150, 154, 158, 162, 165 169 174 178 182 187 191 196 200 205 210 215 221 226 232 237 243 249 255 261 267 274 280 287 2 94, 301, 309, 316, 324, 332, 340, 348, 357, 365, 374, 383, 392, 402, 412, 422, 432, 442, 453, 464, 475, 487, 491, 511, 523, 5 36, 549, 562, 576, 590, 604, 619, 634, 649, 665, 681, 698, 715, 732, 750, 768, 787, 806, 825, 845, 866, 887, 909, 931, 959, 9 76

E192 series: (0.5, 0.25, 0.1 and 0.05% tolerance) 100, 101, 102, 104, 105, 106, 107, 109, 110, 111, 113, 114, 115, 117, 118, 120, 121, 123, 124, 126, 127, 129, 130, 132, 133, 135, 137, 138, 140, 142, 143, 145, 147, 149, 150, 152, 154, 156, 1 58, 160, 162, 164, 165, 167, 169, 172, 174, 176, 178, 180, 182, 184, 187, 189, 191, 193, 196, 198, 200, 203, 205, 208, 210, 2 13, 215, 218, 221, 223, 226, 229, 232, 234, 237, 240, 243, 246, 249, 252, 255, 258, 261, 264, 267, 271, 274, 277, 280, 284, 2 87, 291, 294, 298, 301, 305, 309, 312, 316, 320, 324, 328, 332, 336, 340, 344, 348, 352, 357, 361, 365, 370, 374, 379, 383, 3 88, 392, 397, 402, 407, 412, 417, 422, 427, 432, 437, 442, 448, 453, 459, 464, 470, 475, 481, 487, 493, 499, 505, 511, 517, 5 23, 530, 536, 542, 549, 556, 562, 569, 576, 583, 590, 597, 604, 612, 619, 626, 634, 642, 649, 657, 665, 673, 681, 690, 698, 7 06, 715, 723, 732, 741, 750, 759, 768, 777, 787, 796, 806, 816, 825, 835, 845, 856, 866, 876, 887, 898, 909, 920, 931, 942, 9 53, 965, 976, 988

When designing equipment, it is best to stick to the lowest partition, i.e. it is better to use E6, not E12. So that the number various groups in any equipment was minimized.

To be continued

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 basis 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. Further studies electromagnetic fields and the possibility of their practical use. The course ends, as a rule, with the study of devices that use electrical energy.

To understand electricity, it is not necessary to go to higher or secondary educational institution, just use the tutorial 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 in electromechanics, as a rule, the rules for converting electrical energy into mechanical (how the 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 from scratch this science 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 It is required to obtain a special permit and the presence of specialized education. Do without it official duties prohibited by various regulations. 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

Electrical Engineer. Worked in electrical networks. He specialized in relay protection and electric automation devices. Author of two books from the Electrician's Library series. Published in electrical engineering journals. Currently lives in Israel. 71 years old Pensioner.

Ha-esh`har str., 8\6, Haifa, 35844, Israel

To the reader

It is probably not necessary to explain to you the importance of electricity for the normal functioning of every human being. It would not be an exaggeration to say that today it is the same integral part of it as water, heat, food. And if the lights go out in the house, you, burning your fingers on a lit match, immediately call us.

Electricity travels a long and difficult path before it reaches your home. Produced from fuel at a power plant, it travels through transformer and switching substations, through thousands of kilometers of lines, reinforced on tens of thousands of supports.

Electricity today is a perfect technology, reliable and high-quality power supply, care for the consumer and his service.

However, that's not all. The final link in the electrical chain is the electrical equipment of your home. And it, like any other, requires some knowledge for its proper operation. Therefore, we call on you to cooperate with us and for this purpose we give some recommendations and warnings. Warnings are highlighted in red.

It will be about the following:

1. Legal aspects. The subscriber must be familiar with his rights, duties and responsibilities in relation to the energy supply organization. The same - in relation to the energy supply organization to him.

2. Acquaintance with apartment electrical wiring, switching equipment and installation products.

4. Electricity requires not only certain knowledge, but also strict adherence to certain rules from the user. It is dangerous, both for those who do not know how to use it, and for undisciplined "craftsmen". Therefore, we will introduce you to the basics of electrical safety.

We urge you to treat our recommendations and warnings with understanding. We also hope that you will not cause damage to the network facilities and electrical equipment mentioned above.

We wish you all the best, including those provided by electricity.