Basics of electrical engineering for beginners. Fundamentals of theoretical electrical engineering for beginners. Description of the discipline “Theoretical Foundations of Electrical Engineering”

It’s not a trivial task, I’ll tell you. :) In order to facilitate the assimilation of the material, I introduced a number of simplifications. Completely delusional and anti-scientific, but more or less clearly showing the essence of the process. The “sewer electrics” technique has successfully proven itself in field tests, and therefore will be used here as well. I just want to point out that this is just a visual simplification, valid for the general case and a specific moment in order to understand the essence and has practically nothing to do with the real physics of the process. Why is it then? And to make it easier to remember what’s what and not to confuse voltage and current and understand how resistance affects all this, otherwise I’ve heard enough of this from students...

Current, voltage, resistance.

If you compare an electrical circuit with a sewer system, then the power source is the drain tank, the flowing water is the current, the water pressure is the voltage, and the shit rushing through the pipes is the payload. The higher the cistern, the greater the potential energy of the water in it, and the stronger the pressure-current passing through the pipes, which means the more crap-load it can wash away.
In addition to the flowing crap, the flow is impeded by friction against the walls of the pipes, creating losses. The thicker the pipes, the less loss (gee hee gee now you remember why audiophiles use thicker wires for their powerful acoustics;)).
So, let's summarize. An electrical circuit contains a source that creates a potential difference - voltage - between its poles. Under the influence of this voltage, current rushes through the load to where the potential is lower. The flow of current is hindered by the resistance formed by the payload and losses. As a result, the tension-pressure weakens the more strongly, the greater the resistance. Well, now, let's put our sewerage system in a mathematical channel.

Ohm's law

For example, let's calculate the simplest circuit consisting of three resistances and one source. I will draw the circuit not as is customary in textbooks on TOE, but closer to the real circuit diagram, where they take the point of zero potential - the body, usually equal to the minus of the supply, and the plus is considered a point with a potential equal to the supply voltage. To begin with, we assume that we know the voltage and resistance, which means we need to find the current. Let's add up all the resistances (read the sidebar for the rules for adding resistances) to get the total load and divide the voltage by the resulting result - the current has been found! Now let's see how the voltage is distributed across each resistance. Let's turn Ohm's law inside out and start calculating. U=I*R since the current in the circuit is the same for all series resistances, it will be constant, but the resistances will be different. The result was that Usource = U1 +U2 +U3. Based on this principle, you can, for example, connect 50 light bulbs rated at 4.5 volts in series and easily power them from a 220 volt outlet - not a single light bulb will burn out. What will happen if in this connection, in the middle, you insert one hefty resistance, say one kiloohm, and take the other two smaller ones - one ohm? And from the calculations it will become clear that almost all the voltage will drop across this large resistance.

Kirchhoff's law.

According to this law, the sum of the currents entering and exiting the node is equal to zero, and currents flowing into the node are usually designated with a plus, and currents flowing out with a minus. By analogy with our sewer system, water from one powerful pipe disperses into a bunch of small ones. This rule allows you to calculate the approximate current consumption, which is sometimes simply necessary when calculating circuit diagrams.

Power and losses
The power consumed in a circuit is expressed as the product of voltage and current.
P = U * I
Therefore, the greater the current or voltage, the greater the power. Because The resistor (or wires) does not perform any useful load, then the power falling out of it is a loss in its pure form. In this case, power can be expressed through Ohm’s law as follows:
P= R * I 2

As you can see, an increase in resistance causes an increase in power spent on losses, and if the current increases, then the losses increase quadratically. In the resistor, all the power goes into heating. For the same reason, by the way, batteries heat up during operation - they also have internal resistance, on which part of the energy is dissipated.
This is why audiophiles use thick copper wires with minimal resistance for their heavy-duty sound systems in order to reduce power losses, since there are considerable currents there.

There is a law of total current in a circuit, although in practice it has never been useful to me, but it doesn’t hurt to know it, so grab some textbook on TOE (theoretical foundations of electrical engineering) from the network, it’s better for secondary schools, everything is described there much simpler and more clearly - without going into higher mathematics.

Each of us, when we begin to get involved in something new, immediately rushes into the “abyss of passion”, trying to complete or implement difficult projects homemade. This happened to me when I became interested in electronics. But as usually happens, the first failures diminished the passion. However, I was not used to retreating and began to systematically (literally from the beginning) 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 familiarity with them, continuing to teach the basics would be pointless. Let's just remember that every material is made up of atoms, and each atom in turn has three types of particles. An electron is one of these particles that has a negative charge. Protons have a positive charge. Conducting materials (silver, copper, gold, aluminum, etc.) have many free electrons that move randomly. Voltage is the force that causes electrons to move in a certain direction. A flow of electrons that moves in one direction is called a current. When electrons move through a conductor, they encounter some kind of friction. This friction is called resistance. 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 flowing is in the milliamp range (1 ampere = 1000 milliamps). For example, the typical current for an LED is 20mA.

The unit of measurement for voltage is Volt (V). The battery is a source of voltage. Voltages of 3V, 3.3V, 3.7V and 5V are 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

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

• Batteries;
• Batteries.

Batteries are used once and then disposed of. Batteries can be used several 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 of different types. A few of the most common types used in robotics and engineering projects are:

Batteries 1.5 V

Batteries with this voltage can come in 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 (on load) and with an open circuit voltage of around 3.6V. The capacity can reach from 30 to 500 mAh. Widely used in handheld devices due to their tiny size.

Nickel metal hydride (NiMH)

These batteries have high energy density and can charge 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 products.

3.7V lithium-ion and lithium-polymer batteries

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

9 volt battery

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

Lead-acid

Lead-acid batteries are the workhorse of the entire 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 supply 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 parallel. When connected in series, the voltage increases, and when connected in parallel, the current value increases.

There are two important points 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 contained in it. Capacity represents the maximum amount of energy that can be extracted under certain specified conditions. However, the actual energy storage capacity of a battery may vary significantly from the nominal stated value, and battery capacity is highly dependent on age and temperature, charging or discharging conditions.

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 power - the unit of measurement is Watts (W)) that a 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 longer operation of an electronic device, it is necessary to take batteries with 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 run for about 50 hours: 500 mAh / 10 mA = 50 hours.

With many types of batteries, you cannot "drain" the energy completely (in other words, the battery cannot be completely discharged) without causing serious, and often irreparable, damage to the chemical constituents. The depth of discharge (DOD) of a battery determines the fraction 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.

Charging/discharging rates affect the nominal battery capacity. If the power supply discharges very quickly (ie, the discharge current is high), then the amount of energy that can be extracted 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.

Battery temperature will also affect capacity. At higher temperatures, battery capacity is generally higher than at lower temperatures. However, intentionally increasing the temperature is not an effective way to increase battery capacity, as it 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 produces 1000mA for one hour if the level is 1C. The same battery, at 0.5C, produces 500mA for two hours. With a 2C level, the same battery produces 2000mA for 30 minutes. 1C is often referred to as the one-hour discharge; 0.5C – like a two-hour clock and 0.1C – like a 10-hour clock.

Battery capacity is usually measured using an analyzer. Current analyzers display information as a percentage based on the rated capacity value. A new battery sometimes produces more than 100% current. In this case, the battery is simply rated conservatively and can last longer than what the manufacturer specifies.

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 carefully monitor battery parameters, such as voltage limits and temperature, to prevent overcharging and damage to the battery.

The voltage of a galvanic cell is determined by the chemical reactions that take place inside it. For example, alkaline cells are 1.5 V, all lead acid cells are 2 V, and lithium cells are 3 V. Batteries can be made up of multiple cells, so you will rarely see a 2 V lead acid battery. They are typically wired together internally to provide 6V, 12V, or 24V. Keep in mind that the nominal voltage of a "1.5V" AA battery actually starts at 1.6V, then quickly drops to 1.5, then slowly drifts down to 1.0 V, at which point the battery is considered 'discharged'.

How to choose the best battery for crafts?

As you already understand, there are many types of batteries with different chemical compositions available in the public domain, so it is not easy to choose which power is best for your particular project. If the project is very energy dependent (large sound systems and motorized homemade products) should choose a lead-acid battery. If you want to build a portable under the tree, which will consume little current, then you should choose a lithium battery. For any portable project (light weight and moderate power supply), 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-hungry project, a lithium-ion alkaline (LiPo) battery would be the best option because it is small in size, lightweight 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 proper charge levels and low current charging. 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 current in an electrical circuit.

Resistors are passive components that only consume energy (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 separate I/O lines.

The resistance of a resistor is measured in Ohms. Larger values ​​can be associated with the kilo-, mega-, or giga prefix to make the values ​​easy to read. You can often see resistors labeled kOhm and MOhm range (mOhm resistors are much less common). 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, there are two types of resistors:

• with clearly defined characteristics;
• general purpose, whose characteristics may “walk” (the manufacturer himself indicates the possible deviation).

Example of general characteristics:

• Temperature coefficient;
• Voltage factor;
• Frequency range;
• Power;
• Physical size.

According to their properties, resistors can be classified as:

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

Non linear resistor 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 nonlinear resistors:

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

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

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

Fixed resistors- types of resistors whose value 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 turned or moved manually to change the resistance value over a fixed range, e.g. 0 kOhm to 100 kOhm.

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 resistors is:

Carbon:

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

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 flask of methane 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 sprayed metal in a vacuum onto a ceramic rod base. These types of resistors are very reliable, have high stability and also have a high temperature coefficient. Although they are expensive compared to others, they are used in basic systems.

Wirewound resistor:

A wirewound resistor is made by winding metal wire around a ceramic core. The metal wire is an alloy of various metals selected according to the stated features and resistance of the required resistor. This type of resistor has high stability and can also handle high power, but they are generally bulkier than other types of resistors.

Metal-ceramic:

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

Precision resistors:

Resistors whose resistance value lies within a 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. The tolerance tells us how close to the nominal value the resistance can vary. 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 1% tolerance, the resistance will only change by 1%. So a 500Ω resistor can vary from 495Ω to 505Ω.

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

Fusible resistor:

The wirewound resistor is designed to burn out easily when the rated power exceeds the limiting threshold. Thus the fusible resistor has two functions. When the supply is not exceeded, it serves as a current limiter. When the rated power is exceeded, the oa functions as a fuse; once blown, the circuit becomes open, which protects the components from short circuits.

Thermistors:

A heat-sensitive resistor whose resistance value changes with 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 is always better to check the reference data to know all the specifications of the thermistors.

Photoresistors:

Resistors whose resistance changes 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 the 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.

Leaded and leadless types of resistors:

Terminal 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, into the mounting holes of which the leads of radio elements were soldered.

Surface Mount Resistors:

This type of resistor has become increasingly used since the introduction of surface mount technology. Typically this type of resistor is created by using thin film technology.

Step 4: Standard or Common Resistor Values

The designation system has origins that go back to the beginning of the last century, when most resistors were carbon with relatively poor manufacturing tolerances. The explanation is quite simple - using a 10% tolerance you can reduce the number of resistors produced. It would be ineffective to produce 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, 866 , 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, 294 , 301, 309, 316, 324, 332, 340, 348, 357, 365, 374, 383, 392, 402, 412, 422, 432, 442, 453, 464, 475, 487, 491, 511, 523, 536 , 549, 562, 576, 590, 604, 619, 634, 649, 665, 681, 698, 715, 732, 750, 768, 787, 806, 825, 845, 866, 887, 909, 931, 959, 976

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, 158 , 160, 162, 164, 165, 167, 169, 172, 174, 176, 178, 180, 182, 184, 187, 189, 191, 193, 196, 198, 200, 203, 205, 208, 210, 213 , 215, 218, 221, 223, 226, 229, 232, 234, 237, 240, 243, 246, 249, 252, 255, 258, 261, 264, 267, 271, 274, 277, 280, 284, 287 , 291, 294, 298, 301, 305, 309, 312, 316, 320, 324, 328, 332, 336, 340, 344, 348, 352, 357, 361, 365, 370, 374, 379, 383, 388 , 392, 397, 402, 407, 412, 417, 422, 427, 432, 437, 442, 448, 453, 459, 464, 470, 475, 481, 487, 493, 499, 505, 511, 517, 523 , 530, 536, 542, 549, 556, 562, 569, 576, 583, 590, 597, 604, 612, 619, 626, 634, 642, 649, 657, 665, 673, 681, 690, 698, 706 , 715, 723, 732, 741, 750, 759, 768, 777, 787, 796, 806, 816, 825, 835, 845, 856, 866, 876, 887, 898, 909, 920, 931, 942, 953 , 965, 976, 988

When designing hardware, it is best to stick to the lowest section, i.e. It's better to use E6 rather than E12. In such a way that the number of different groups in any equipment is minimized.

To be continued

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

The basics of electrical engineering for beginners, presented in accessible language, will help you gain knowledge in this area. Supported by historical facts and clear examples, they become fascinating and understandable even for those who are encountering unfamiliar concepts for the first time. 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 carrying out any calculations. They are also needed by those who practically perform operations related to electricity. Knowing the basics of electrical engineering, you can logically determine the cause of the malfunction and eliminate it very quickly.

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

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

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

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

Basic current quantities

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

In order to create and maintain the movement of charged particles, it is necessary to have a force applied to them in a certain direction. If this action stops, the flow of electric current also stops. This force is called the electric field, also known as. It is this that 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 basic 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 Omaha. This value is a kind of resistance of the conductor to the flow of electric current in it. As a result of the influence of resistance, the conductor heats up. As the length of the conductor increases and its cross-section decreases, the resistance value increases. A value of 1 ohm occurs when the potential difference in the conductor is 1 V and the current is 1 A.

Ohm's law

This law relates to the basic provisions and concepts of electrical engineering. It most accurately reflects the relationship between quantities such as current, voltage, resistance, etc. 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 = 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 with a pipe adjacent to it is installed. When the valve opens, 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 arises at the ends of the conductor in the form of a potential difference - voltage, under the influence of which electrons move along the conductor. Thus, by analogy, voltage is a kind of electrical pressure.

The current strength can be compared with the water flow, that is, the amount of water flowing through the cross-section of the pipe over a set period of time. As the pipe diameter decreases, the water flow will also decrease due to increased 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 related to 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 electrical energy 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 power, that is, the amount of energy that a particular device can consume. This parameter is calculated by the formula P = 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 you understand the basic concepts and terms at first. After this, it will be much easier to use the acquired knowledge in practice.

Electrics for dummies: electronics basics

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

Features of the term

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

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

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

AC transmission circuit

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

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

An electrical panel in the apartment is necessary for current in all rooms. are considered economically feasible, since they do not require two. When approaching the consumer, the current is divided into three phases, each with a zero. The ground electrode, which is used in a single-phase network, does not carry a working load. He is a fuse.

For example, if a short circuit occurs, there is a threat of electric shock or fire. To prevent such a situation, the current value should not exceed a safe level; the excess goes into the ground.

The manual “School for Electricians” will help novice craftsmen cope with some breakdowns of household appliances. For example, if there are problems with the functioning of the electric motor of the washing machine, current will flow to the outer metal casing.

If there is no grounding, the charge will be distributed throughout the machine. When you touch it with your hands, a person will act as a grounding conductor and receive an electric shock. If there is a ground wire, this situation will not arise.

Features of electrical engineering

The textbook “Electricity for Dummies” is popular among those who are far from physics, but plan to use this science for practical purposes.

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

The “School for Electrician” manual assumes familiarity with the basic terms related to electricity.

Many physics books contain complex electrical diagrams and a variety of confusing terms. In order for beginners to understand all the intricacies of this section of physics, a special manual “Electricity for Dummies” was developed. An excursion into the world of the electron must begin with a consideration of theoretical laws and concepts. Illustrative examples and historical facts used in the book “Electricity for Dummies” will help novice electricians acquire knowledge. To check your progress, you can use assignments, tests, and exercises related to electricity.

If you understand that you do not have enough theoretical knowledge to independently cope with connecting electrical wiring, refer to reference books for “dummies”.

Safety and Practice

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

In order to put into practice the theoretical knowledge gained after self-studying the basics of electrical engineering, you can start with old household appliances. Before starting repairs, be sure to read the instructions included with the device. Don't forget that you shouldn't joke with electricity.

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

For free electrons to move from one pole to another, there must be a certain potential difference between them.

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

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

Conclusion

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

Everyone has a certain power. It refers to the amount of electricity generated by a device over a certain period of time. Energy consumers (refrigerators, washing machines, kettles, irons) also have power, consuming electricity during operation. If you wish, you can carry out mathematical calculations and determine the approximate price for each household appliance.

Electrical engineering is like a foreign language. Some have already mastered it perfectly for a long time, others are just beginning to get acquainted with it, and for others it is still an unattainable, but alluring goal. Why do many people want to explore this mysterious world of electricity? People have been familiar with it for only about 250 years, but today it is difficult to imagine life without electricity. To get acquainted with this world, there are theoretical foundations of electrical engineering (TOE) for dummies.

First acquaintance with electricity

At the end of the 18th century, the French scientist Charles Coulomb began to actively study the electrical and magnetic phenomena of substances. It was he who discovered the law of electric charge, which was named after him - the coulomb.

Today it is known that any substance consists of atoms and electrons rotating around them in an orbital. However, in some substances, electrons are held very tightly by atoms, while in others this bond is weak, which allows electrons to freely break away from some atoms and attach to others.

To understand what it is, you can imagine a large city with a huge number of cars that move without any rules. These machines move chaotically and cannot do useful work. Fortunately, the electrons do not break apart, but bounce off each other like balls. To benefit from these little workers , three conditions must be met:

1. Atoms of a substance must freely give up their electrons.
2. A force must be applied to this substance, which will force the electrons to move in one direction.
3. The circuit along which charged particles move must be closed.

It is the observance of these three conditions that underlies electrical engineering for beginners.

All elements are made up of atoms. Atoms can be compared to the solar system, only each system has its own number of orbits, and each orbit can contain several planets (electrons). The further the orbit is from the nucleus, the less attraction the electrons in this orbit experience.

Attraction does not depend on the mass of the nucleus, but from different polarities of the nucleus and electrons. If the nucleus has a charge of +10 units, the electrons must also have a total of 10 units, but of a negative charge. If an electron flies away from the outer orbit, then the total energy of the electrons will already be -9 units. A simple example for addition +10 + (-9) = +1. It turns out that the atom has a positive charge.

It also happens the other way around: the nucleus has a strong attraction and captures a “foreign” electron. Then an “extra”, 11th electron appears in its outer orbit. Same example +10 + (-11) = -1. In this case, the atom will be negatively charged.

If two materials with opposite charges are placed in an electrolyte and connected to them through a conductor, for example, a light bulb, then current will flow in a closed circuit and the light bulb will light up. If the circuit is broken, for example through a switch, the light bulb will go out.

Electric current is obtained as follows. When one of the materials (electrode) is exposed to an electrolyte, an excess of electrons appears in it, and it becomes negatively charged. The second electrode, on the contrary, gives up electrons when exposed to the electrolyte and becomes positively charged. Each electrode is respectively designated “+” (excess electrons) and “-” (lack of electrons).

Although electrons have a negative charge, the electrode is marked “+”. This confusion occurred at the dawn of electrical engineering. At that time, it was believed that charge transfer occurs by positive particles. Since then, many circuits have been drawn up, and in order not to redo them, they left everything as is .

In galvanic cells, electric current is generated as a result of a chemical reaction. The combination of several elements is called a battery; such a rule can be found in electrical engineering for dummies. If the reverse process is possible, when chemical energy accumulates in the element under the influence of electric current, then such an element is called a battery.

The galvanic cell was invented by Alessandro Volta in 1800. He used copper and zinc plates dipped in a salt solution. This became the prototype of modern batteries and batteries.

Types and characteristics of current

After receiving the first electricity, the idea arose to transmit this energy over a certain distance, and here difficulties arose. It turns out that electrons passing through a conductor lose part of their energy, and the longer the conductor, the greater these losses. In 1826, Georg Ohm established a law that traces the relationship between voltage, current and resistance. It reads as follows: U=RI. In words, it turns out: voltage is equal to the current multiplied by the resistance of the conductor.

From the equation it can be seen that the longer the conductor, which increases the resistance, the less current and voltage will be, therefore, the power will decrease. It is impossible to eliminate resistance; to do this, you need to lower the temperature of the conductor to absolute zero, which is only possible in laboratory conditions. Current is necessary for power, so you can’t touch it either, all that remains is to increase the voltage.

For the end of the 19th century, this was an insurmountable problem. After all, at that time there were no power plants generating alternating current, no transformers. Therefore, engineers and scientists turned their attention to radio, although it was very different from modern wireless. The governments of various countries did not see the benefits of these developments and did not sponsor such projects.

To be able to transform the voltage, increase or decrease it, alternating current is required. You can see how this works in the following example. If the wire is rolled into a coil and a magnet is quickly moved inside it, an alternating current will arise in the coil. This can be verified by connecting a voltmeter with a zero mark in the middle to the ends of the coil. The arrow of the device will deviate to the left and to the right, this will indicate that the electrons are moving in one direction, then in the other.

This method of generating electricity is called magnetic induction. It is used, for example, in generators and transformers, receiving and changing current. According to its form alternating current can be:

• sinusoidal;
• impulsive;
• straightened.

Types of conductors

The first thing that affects electric current is the conductivity of the material. This conductivity is different for different materials. Conventionally, all substances can be divided into three types:

• conductor;
• semiconductor;
• dielectric.

A conductor can be any substance that freely passes electric current through itself. These include hard materials such as metal or semi-metal (graphite). Liquid - mercury, molten metals, electrolytes. This also includes ionized gases.

Based on this, conductors are divided into two types of conductivity:

• electronic;
• ionic.

Electronic conductivity includes all materials and substances that use electrons to create an electric current. These elements include metals and semimetals. Carbon also conducts current well.

In ionic conduction, this role is played by a particle that has a positive or negative charge. An ion is a particle with a missing or extra electron. Some ions are not averse to capturing an “extra” electron, while others do not value electrons and therefore freely give them away.

Accordingly, such particles can be negatively charged or positively charged. An example is salt water. The main substance is distilled water, which is an insulator and does not conduct current. When salt is added, it becomes an electrolyte, that is, a conductor.

Semiconductors in their normal state do not conduct current, but when exposed to external influences (temperature, pressure, light, etc.) they begin to conduct current, although not as well as conductors.

All other materials not included in the first two types are classified as dielectrics or insulators. Under normal conditions, they practically do not conduct electric current. This is explained by the fact that in the outer orbit the electrons are held very firmly in their places, and there is no room for other electrons.

When studying electrics for dummies, you need to remember that all the previously listed types of materials are used. Conductors are primarily used to connect circuit elements (including in microcircuits). They can connect a power source to a load (for example, a cord from a refrigerator, electrical wiring, etc.). They are used in the manufacture of coils, which, in turn, can be used unchanged, for example, on printed circuit boards or in transformers, generators, electric motors, etc.

The conductors are the most numerous and diverse. Almost all radio components are made from them. To obtain a varistor, for example, a single semiconductor (silicon carbide or zinc oxide) can be used. There are parts that contain conductors of different types of conductivity, for example, diodes, zener diodes, transistors.

Bimetals occupy a special niche. It is a combination of two or more metals, which have different degrees of expansion. When such a part heats up, it deforms due to different percentage expansion. Typically used in current protection, for example, to protect an electric motor from overheating or to turn off the device when it reaches a set temperature, as in an iron.

Dielectrics mainly serve a protective function (for example, insulating handles on power tools). They also allow you to isolate elements of an electrical circuit. The printed circuit board on which the radio components are mounted is made of dielectric. The coil wires are coated with insulating varnish to prevent short circuits between turns.

However, a dielectric, when a conductor is added, becomes a semiconductor and can conduct current. The same air becomes a conductor during a thunderstorm. Dry wood is a poor conductor, but if it gets wet, it will no longer be safe.

Electric current plays a huge role in the life of modern man, but, on the other hand, it can pose a mortal danger. It is very difficult to detect it, for example, in a wire lying on the ground; this requires special equipment and knowledge. Therefore, extreme caution must be exercised when using electrical appliances.

The human body is composed primarily of water, but it is not distilled water, which is a dielectric. Therefore, the body becomes almost a conductor for electricity. After receiving an electric shock, the muscles contract, which can lead to cardiac and respiratory arrest. With further action of the current, the blood begins to boil, then the body dries out and, finally, the tissues become charred. The first thing to do is to stop the current, if necessary, provide first aid and call doctors.

Static voltage occurs in nature, but most often it does not pose a danger to humans, with the exception of lightning. But it can be dangerous for electronic circuits or parts. Therefore, when working with microcircuits and field-effect transistors, grounded bracelets are used.