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 is like a two-hour clock and 0.1C is 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 battery types, 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
Welcome to the electrical training video course. This video tutorial will help everyone who deals with electricity at home, as well as many novice electricians, to understand the basic terms and skills. A training video course by a young electrician will help you in life and save your life from electric shock.
Young electrician course
The author of the course, Vladimr Kozin, will help you learn with video examples what an electrical circuit is and how it consists and works. You will learn how an electrical circuit works with a switch, as well as with a two-gang switch.
Brief course content: The video course consists of 5 parts, each with 2 lessons. course Young electrician course with a total duration of about 3 hours.
- In the first part you will be introduced to the basics of electrical engineering, consider the simplest diagrams for connecting light bulbs, switches, sockets and learn about the types of electrician's tools;
- In the second part you will be told about the types and purposes of materials for the work of an electrician: cables, wires, cords and you will assemble a simple electrical circuit;
- In the third part you will learn how to connect a switch and parallel connections in electrical circuits;
- In the fourth part you will see the assembly of an electrical circuit with a two-button switch and a model of the power supply of the room;
Ultimate learning goal: In the fifth part, you will consider a complete model of the electrical supply of a room with a switch and receive tips on safety when working with electrical equipment.
Lesson 1. Young electrician course.
Lesson 2. Electrician's tool.
Lesson 3. Materials for electrical installation cable AVVG and VVG.
Lesson 4. Simple electrical circuit.
Lesson 5. Electric circuit with a switch.
Lesson 6. Parallel connection.
Lesson 7. Electric circuit with a two-gang switch
Lesson 8. Premises power supply model
Lesson 9. Model of power supply for a room with automatic shutdown
Lesson 10. Safety.
The electrician profession has been and will be in demand, because... Every year, electricity consumption is only increasing, and electrical networks are spreading more and more throughout the planet. In this article we want to tell readers how to become an electrician from scratch, where to start and where to study in order to be a professional in your field.
First of all, it should be noted that an electrician can be an electrician, an electronics engineer, an auto electrician, an electrical engineer, a designer, an electromechanic, an electrical engineer, and even a power engineer, in general. As you understand, each profession has its own characteristics. To become an electrician, first you must choose a suitable specialty with which you decide to further connect your life or a separate period of time.
Our advice is that if you are really interested in everything related to electricity, it is better to plan ahead, choosing promising areas that are the key to scientific and technological progress. A very interesting job today is the profession of a power supply designer or an auto electrician diagnostician.
Where to start learning?
Today, you can become an electrician from scratch by studying at a university, technical school, college, vocational school, or even taking special emergency courses. It cannot be said that a higher educational institution is the foundation through which one can become a professional electrical installer. Quite a lot of specialists are generally self-taught, who graduated from technical school just to get their degrees and get a job at an enterprise.
Let's look at some of the most popular ways to become an electrician:
- University Duration of training is from 4 to 5.5 years. Graduates can be engineers because... undergo the most comprehensive theoretical and practical course. Training may be free.
- Technical College. When entering after 9th grade, the course of study lasts from 3 to 4 years. After 11th grade, you will have 1.5 to 3 years to study. The qualification that graduates receive is a technician. There is an opportunity to study for free.
- College, vocational school – training from 1 to 3 years. After graduation, you can become an electrician repairing electrical equipment. As in the two previous cases, you can get education for free.
- Emergency courses – from 3 weeks to 2 months. The fastest way to become an electrician from scratch. Today, you can even learn a profession online thanks to Skype conferences and individual training. The cost of courses ranges from 10 to 17 thousand rubles (prices for 2017).
- Self-learning. Only suitable if you want to become an electrician at home. There are many books, paid courses and even websites, like ours, where you can learn almost everything in order to do simple electrical installation work yourself. We will dwell in more detail on this method, which allows you to become a competent electrician from scratch.
First steps to learning
A few words about self-taught
If you are interested in the profession of an electrician only in order to independently perform simple electrical installation work, then it will be enough to study all the material from books and video courses, and then carry out simple connections and repairs from scratch. More than once we have met quite competent electricians who performed complex work without education, and we can say with confidence that they did it very professionally. At the same time, there were also would-be electricians with higher education, whom one would not dare call engineers.
All this leads to the fact that it is possible to become an electrician at home, but it still won’t hurt to consolidate the knowledge gained by taking courses. Another way to learn all the necessary skills is to ask to be an electrician’s assistant at a construction site. You can also advertise on various forums that you agree to help electrical installers on their “coven” for free or for a small percentage of the profit. Many specialists will not refuse help, such as “lifting it to the floor,” drilling it, or helping with something else for a couple of hundred rubles. You, in turn, will be able to gain experience by watching a master at work. After a few months of such mutually beneficial work, you can start connecting sockets, circuit breakers, or even repairing lamps yourself. And then only experience and new objects will help you become a good electrician without education.
Well, the last thing we recommend is to learn the basics using our advice. To begin with, you can study the section, then go to and so on for all sections. In addition to this, it would not hurt to study the books that we will also talk about and find a suitable video course. As a result, if you have the desire and you pay attention to all the assigned tasks, you will certainly succeed in becoming an electrician at home.
So that you understand the prospects of such a profession, today there are a lot of lawyers, economists and other specialties where mental work is more needed. But enterprises are sorely short of labor. As a result, if you really want to, you can learn and find a high-paying job if you really show yourself as a specialist. The average salary of an electrician for 2017 is 35,000 rubles. Taking into account additional on-call work and an increase in rank, it will not be difficult to earn much more - from 50,000 rubles. These figures already clarify the picture more about whether it is promising to become an electrician.
In addition to all that has been said, I would like to recommend several sources of information:
- – the minimum set must be present from the very beginning of training.
- – a section in which we consider all the nuances and dangerous situations that you, as a beginner, should know about. Do not forget that the profession of an electrician has its main disadvantage - the work is dangerous, because... you will be dealing with electrical current.
CONTENT:
INTRODUCTION
TYPE OF WIRE
PROPERTIES OF CURRENT
TRANSFORMER
HEATING ELEMENTS
ELECTRICITY HAZARD
PROTECTION
AFTERWORD
POEM ABOUT ELECTRIC CURRENT
OTHER ARTICLES
INTRODUCTION
In one of the episodes of "Civilization" I criticized the imperfection and cumbersomeness of education, because it, as a rule, is taught in a studied language, stuffed with incomprehensible terms, without clear 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 simple and understandable language.
I am convinced that all difficult sciences, especially those describing phenomena that a person cannot comprehend with his five senses (vision, hearing, smell, taste, touch), for example, quantum mechanics, chemistry, biology, electronics, should be taught in the form of comparisons and examples. And even better - create colorful educational cartoons about invisible processes inside matter. Now in half an hour I will turn you into electrically and technically literate people. And so, I begin to describe the principles and laws of electricity using figurative comparisons...
VOLTAGE, RESISTANCE, CURRENT
You can rotate the wheel of a water mill with a thick jet with low pressure or a thin jet with high pressure. The pressure is the voltage (measured in VOLTS), the thickness of the jet is the current (measured in AMPERES), and the total force striking the wheel blades is the power (measured in WATTS). A 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 options is the same.
The voltage in the network (socket) is stable (220 Volts), but 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, on the kettle it is written - Power 2.2 kW, which means 2200 W (W) - Watt, divided by voltage (Voltage) 220 V (V) - Volt, we get 10 A (Ampere) - the current that flows at operation of the kettle. Now we divide the voltage (220 Volts) by the operating current (10 Amperes), we get the resistance of the kettle - 22 Ohms (Ohms).
By analogy with water, resistance is similar to a pipe filled with a porous substance. To push water through this cavernous tube, a certain pressure (voltage) is required, and the amount of liquid (current) will depend on two factors: this pressure, and how permeable the tube is (its resistance). This comparison is suitable for heating and lighting devices, and is called ACTIVE resistance, and the resistance of the electrical coils. motors, transformers and electrical magnets work differently (more on this later).
FUSES, CIRCUIT MEASURES, TEMPERATURE REGULATORS
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 email from this. fuses or automatic switches (automatic circuit breakers) are installed in the wiring. The principle of operation of the fuse (fuse link) is extremely simple; it is a deliberately thin place in the electrical circuit. chains, and where they are thin, they break. A thin copper wire is inserted into a ceramic heat-resistant cylinder. The thickness (section) of the wire is much thinner than the electric one. wiring. When the current exceeds the permissible 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, to protect electrical wiring, it is not fuses that are used, but circuit breakers (circuit breakers). The machines have two protection functions. One is triggered when too many electrical appliances are connected to the network and the current exceeds the permissible limit. This is a bimetallic plate made of two layers of different metals, which when heated do not expand equally, 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 inhomogeneity) and opens the contacts. It is usually not possible to turn the machine back on right away 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 not heated by an exorbitant current passing through it, but directly by the heating element of the device itself, to which the sensor is tightly screwed. In devices with desired temperature (irons, heaters, washing machines, water heaters), the shutdown limit is set by the handle of the thermostat, inside of which there is also a bimetallic plate. It then opens and then closes the contacts maintaining the set temperature. As if, without changing the strength of the fire of the burner, then set there is a kettle on it, then remove it.)
There is also a coil of thick copper wire inside the machine, through which all the operating current also passes. When there is a short circuit, the force of the magnetic field of the coil reaches a power that compresses the spring and retracts the 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 circuits) and long-term overloads.
TYPE OF WIRE
Electrical wiring wires are either aluminum or copper. The maximum permissible current depends on their thickness (section in square millimeters). For example, 1 square millimeter of copper can withstand 10 Amps. Typical wire cross-section standards: 1.5; 2.5; 4 "squares" - respectively: 15; 25; 40 Amps is their permissible long-term current load. Aluminum wires withstand current less than 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 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.
PROPERTIES OF CURRENT
Electric current requires a closed circuit. By analogy with a bicycle, where the leading star with pedals corresponds to the electrical source. energy (generator or transformer), the star on the rear wheel is an electrical appliance that we plug into the network (heater, kettle, vacuum cleaner, TV, etc.). The upper section of the chain, which transfers force from the drive to the rear sprocket, is similar to the potential with voltage - phase, and the lower section, 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 flows, and a return pipe through which the water leaves, giving off heat in the batteries (radiators).
There are two types of currents - constant and alternating. Natural direct current that flows in one direction (like water in a heating system or a bicycle chain) 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 using semiconductor diode “bridges”, which can be compared to the latch of a door lock - it is let through in one direction, and 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 out the pulses, capacitors (capacitance) are installed. Their principle can be compared to a large, full barrel, into which a “ragged” and intermittent stream is poured, and from its tap at the bottom, water flows out steadily and evenly, and the larger the volume of the barrel, the better the quality of the stream. 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 el. engines can only work 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 out and draw in water. Then the mouth will be similar to potential with voltage - phase, and a 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 the movement will be the voltage (V), the force of the hand will be the current (A), the energy will be the frequency (Hz), and the log itself will be the electric power. a device (heater or electric motor), only instead of sawing - useful work. Sexual intercourse is also suitable for figurative comparison, a man is a “phase”, a woman is ZERO!, amplitude (length) is voltage, thickness is current, speed is frequency.
The number of oscillations is always the same, and always the same as that produced at the power plant and supplied to the network. In Russian networks, the number of oscillations is 50 times per second, and is called the alternating current frequency (from the word often, not purely). The unit of frequency measurement is HERZ (Hz), that is, in our sockets it is always 50 Hz. In some countries, the frequency in networks is 100 Hertz. The rotation speed of most electric devices depends on the frequency. engines. At 50 Hertz the maximum speed is 3000 rpm. - on three-phase power supply and 1500 rpm. - on single-phase (household). Alternating current is also needed to operate transformers that step down high voltage (10,000 Volts) to normal household or industrial voltage (220/380 Volts) in electrical substations. And also for small transformers in electronic equipment that reduce 220 Volts to 50, 36, 24 Volts and below.
TRANSFORMER
The transformer consists of electrical iron (assembled 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 on top of the primary (or on an adjacent coil) from 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 appears around the iron, which induces current in the secondary winding. How many times there are fewer turns in it (the secondary one) - the voltage will be lower by the same amount, and how many times the wire is thicker - how much more current can be drawn. As if, a barrel of water will be filled with a thin stream, but with enormous pressure, and from below, a thick stream will flow out of a large tap, but with moderate pressure. Similarly, transformers can be the opposite - 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 16-20 meters. That is, to wind a spiral at an operating voltage of 36 Volts, you need to divide 220 by 36, which is 6. This means that the length of the wire of a 36 Volt spiral will be 6 times shorter, approximately 3 meters. If the coil 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 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 under a voltage of 380: 2 = 190 Volts. That is, 30 Volts less than the calculated voltage. In this mode, they will heat up a little (15%) less, but they will never burn out. The same with light bulbs, for example, you can connect 10 identical 24 Volt light bulbs in series and turn them on as a garland to a 220 Volt network.
HIGH VOLTAGE POWER LINES
It is advisable to transmit electricity over long distances (from a hydro or nuclear power plant to a city) only under high voltage (100,000 Volts) - this way the thickness (cross-section) of wires on the supports of overhead power lines can be kept to a minimum. If electricity were transmitted immediately under low voltage (as in sockets - 220 Volts), then the wires of the overhead lines would have to be made as thick as logs, and no reserves of aluminum would be enough for this. In addition, high voltage more easily overcomes the resistance of the wire and connection contacts (for aluminum and copper it is negligible, but over a length of tens of kilometers it still builds up significantly), like a motorcyclist rushing at breakneck speed who easily flies over holes and ravines.
ELECTRIC MOTORS AND THREE-PHASE POWER
One of the main needs for alternating current is asynchronous electric power. engines that are widely used due to their simplicity and reliability. Their rotors (the rotating part of the engine) do not have a winding and a commutator, but are simply blanks made of electrical iron, in which the slots for the winding are filled with aluminum - in this design there is nothing to break. They rotate due to the alternating magnetic field created by the stator (the stationary part of the electric motor). To ensure proper operation of the electrical For motors of this type (and the vast majority of them), 3-phase power supply prevails everywhere. The phases as three twin sisters are no different. Between each of them and zero there is a voltage of 220 Volts (V), the frequency of each is 50 Hertz (Hz). They differ only in the time shift and “names” - A, B, C.
The graphical representation of alternating current of one phase is depicted in the form of a wavy line that wags like 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 reflects the time) and again reaches the peak (220 V) on the lower side. The distance between waves along a straight line expresses the frequency (50 Hz). The three phases on the graph represent 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 declining, and so on one by one - like a gymnastics 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 press alternately like phases, only here there are, as it were, three pedals located relative to each other at an angle of 120 degrees (like the Mercedes emblem or a three-blade airplane propeller).
Three electrical windings motor (each phase has its own) are depicted in the diagrams in the same way, like a propeller with three blades, some ends connected at a common point, the other to the phases. The windings of three-phase transformers at substations (which reduce high voltage to household voltage) are connected in the same way, and ZERO comes from the common connection point of the windings (the neutral of the transformer). Generators producing electricity. energy have a similar pattern. In them, the mechanical rotation of the rotor (via a hydro or steam turbine) is converted into electricity in power plants (and in small mobile generators - via an internal combustion engine). The rotor, with its magnetic field, induces electric current in the three stator windings with a lag of 120 degrees around the circumference (like the Mercedes emblem). The result is a three-phase alternating current with multi-time pulsation, creating a rotating magnetic field. Electric motors, on the other hand, convert three-phase current through a magnetic field into mechanical rotation. The wires of the windings have no resistance, but the current in the windings limits the magnetic field created by their turns around the iron, like the force of gravity acting on a cyclist riding uphill and preventing him from accelerating. The resistance of the magnetic field limiting the current is called INDUCTION.
Due to the phases lagging behind each other and reaching their peak voltage at different instants, a potential difference is obtained between them. This is called line voltage, and in household networks it is 380 Volts (V). Linear (phase-to-phase) voltage is always 1.73 times greater than phase voltage (between phase and zero). This coefficient (1.73) is widely used in calculation formulas for three-phase systems. For example, the current of each phase of the electric. motor = power in Watts (W) divided by line voltage (380 V) = total current in all three windings, which we also divide by the coefficient (1.73), we get the current in each phase.
Three-phase power supply creating a rotational effect for the electric power. engines, due to the universal standard, provides power supply to domestic buildings (residential, office, commercial, educational buildings) - where there is electricity. engines are not used. As a rule, 4-wire cables (3 phases and zero) come to general distribution panels, and from there they disperse 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, which comes to the electric power supply, is often overloaded. 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 electric power. appliances (such as a kettle, heater, washing machine, water heater), and the other has low-power ones (TV, computer, audio equipment), then the 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 out his equipment, including the refrigerator. Therefore, it is advisable to regularly check the reliability of the contact of the zero coming from the supply cable with the general electrical distribution board. And if it gets hot, then turn off the circuit breakers in all apartments, clean off the carbon deposits and thoroughly tighten the common zero contact. With relatively equal loads on different phases, a larger share of reverse currents (through the common connection point of consumer zeros) will be mutually absorbed by neighboring phases. In three-phase electric In motors, the phase currents are equal and completely disappear through adjacent phases, so they do not need zero at all.
Single-phase electric motors operate from one phase and zero (for example, in household 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 intersects the field of the first (working) winding at 90 degrees. The starting winding has a capacitor (capacitance) in the circuit, which shifts its pulses 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 electric. engines cannot be more than 1500 rpm. In three-phase electric In engines, the coils can be single, located in the stator every 120 degrees around the circumference, then the maximum rotation speed will be 3000 rpm. And if they are each divided in half, 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 greater. There may be 9 or 12 coils, respectively 1000 and 750 rpm, with an increase in force the same times as the number of revolutions per minute is lower. The windings of single-phase motors can also be cut more than in half, with a similar reduction in speed and increase in force. That is, a low-speed engine is more difficult to hold onto the rotor shaft with anything than a high-speed engine.
There is another common type of email. engines - commutator. Their rotors carry a winding and a contact collector, to which voltage is supplied through copper-graphite “brushes”. It (the rotor winding) creates its own magnetic field. Unlike the passively untwisted iron-aluminum “blank” of asynchronous electric. engine, the magnetic field of the rotor winding of the commutator motor is actively repelled from the field of its stator. Such emails engines have a different operating principle - like the two poles of a magnet of the same name, the rotor (the rotating part of the electric motor) tends to push off from the stator (the stationary part). And since the rotor shaft is firmly fixed by two bearings at the ends, out of “despair” the rotor is actively twisted. The effect is similar to a squirrel in a wheel, the faster it runs, the faster the drum spins. Therefore, such emails motors have much higher speeds and can be adjusted over a wide range than asynchronous ones. In addition, with the same power, they are much more compact and lighter, do not depend on frequency (Hz) and operate on both alternating and direct current. They are usually used in mobile units: electric train locomotives, trams, trolleybuses, electric cars; as well as in all portable el. devices: electric drills, grinders, vacuum cleaners, hair dryers... But they are significantly inferior in simplicity and reliability to asynchronous machines, 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 a 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, el. current is fraught with mortal danger for a living organism through which it can pass.
Some people say: “I was hit by 220 volts.” This is not true because it is not the voltage that causes damage, but the current that passes through the body. Its value, at the same voltage, can differ tens of times for a number of reasons. The path it takes is also of great importance. In order for current to flow through the body, you must be part of an electrical circuit, that is, 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 flow of current is from one hand to the other, or from the left hand to the legs, because this way the path will go through the heart, which can stop from 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, but will not affect the body (unless, of course, your feet are on a non-conductive floor).
The role of zero potential (ZERO) can be played by the ground - literally the soil surface itself (especially damp), or a metal or reinforced concrete structure that is dug into the ground or has a significant area of contact 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 floors and touch the exposed wire with any part of your body. And instantly from this part, an insidious current will flow through the body to the feet. Even if you go to relieve yourself in the bushes and accidentally hit the exposed phase with a stream, the current path will run through the (salty and much more conductive) stream of urine, the reproductive system and legs. If your feet are wearing dry shoes with thick soles or the floor itself is wooden, then there will be no ZERO and no current will flow even if you grab one exposed live PHASE wire with your teeth (a clear confirmation of this is birds sitting on uninsulated 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. Or you can grab two thick copper rods, to which only 50 Volts are connected, with both wet hands - the contact area + dampness will provide conductivity tens of 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 calloused, dry and calloused that he could easily work under voltage as if wearing gloves.) In addition, when a person touches the voltage with his fingertips or the back of his hand, he reflexively jerks away. If you grab hold of a handrail, then the tension causes contraction of the muscles of the hands and the person grabs with a force that he was never capable of, and no one can tear him off until the tension is turned off. And the time of exposure (milliseconds or seconds) to electric current is also a very significant factor.
For example, in the electric chair, a tightly tightened wide metal hoop is placed on a person’s previously shaved head (through a rag pad moistened with a special, well-conducting solution), to which one wire is connected - the phase one. The second potential is connected to the legs, on which (on the shins near the ankles) wide metal clamps (again with wet special pads) are tightly tightened. The condemned person is securely fixed to the armrests of the chair by his forearms. When you turn on the switch, a voltage of 2000 Volts appears between the potentials of the head and legs! It is understood that with the resulting 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 don’t be alarmed - there is no such execution in our state yet...
And so, the danger of electric shock. current depends on: voltage, path of current flow, dry or wet (sweat due to salts has good conductivity) parts of the body, area of contact with bare conductors, isolation of feet from the ground (quality and dryness of shoes, soil dampness, floor material), time exposure to current.
But you don’t have to grab a bare wire to get energized. It may happen that the insulation of the winding of the electrical unit is broken, and then the PHASE will end up on its body (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 therefore salty) thighs, and began drilling into the ceiling with an electric drill, holding onto its metal part near the chuck with his other hand... Either it got into the reinforcement (and it is usually welded to the general grounding loop of the building, which is equivalent to ZERO) of the concrete ceiling slab, or into its own electrical wiring?? He just fell down dead, struck on the spot by a monstrous electric shock. The commission discovered a PHASE (220 volts) on the body of the refrigerator, which appeared on it due to a violation of the insulation of the compressor stator winding. Until you simultaneously touch the body (with the hidden phase) and zero or “ground” (for example, an iron water pipe), nothing will happen (chipboard and linoleum on the floor). But, as soon as the second potential is “found” (ZERO or another PHASE), a blow is inevitable.
To prevent such accidents, GROUNDING is done. That is, through a special protective grounding wire (yellow-green) to the metal housings of all electrical devices. devices are connected to ZERO potential. If the insulation is broken and the PHASE touches the housing, 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, ground - yellow-green wires) wiring in single-phase power supply, and five-wire in three-phase (phases - red, white, brown). In the so-called Euro-sockets, in addition to two sockets, grounding contacts (whiskers) were also added - a yellow-green wire is connected to them, and on Euro-plugs, in addition to two pins, there are contacts from which a yellow-green (third) wire also goes to the body electrical appliance.
To avoid short circuits, RCDs (residual current devices) have recently been widely used. The RCD compares the phase and zero currents (how much is in and how much is out), and when a leak appears, that is, either the insulation is broken, and the winding of the motor, transformer or heater spiral is “stitched” onto the housing, or a person actually touches the current-carrying parts, then the “zero” current will be less than the phase current and the RCD will instantly turn off. This 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 supply this limit is usually 30 mA. Such devices are usually placed at the input (in series with circuit breakers) of the wiring supplying damp, hazardous rooms (for example, a bathroom) and protect against electric shock from hands - to the “ground” (floor, bathtub, pipes, water). Touching the phase and working zero with both hands (with a non-conducting floor) will not trigger the RCD.
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 also connected to a large metal rod dug deep into the ground - GROUNDING at the electrical substation supplying the microdistrict). Practically, this is the same zero, but “exempt” from work, just a “guard”. So, in the absence of a ground wire in the wiring, you can use a neutral wire. Namely, in a Euro socket, place a jumper from the neutral wire to the grounding “whiskers”, then if the insulation is broken and there is a leak to the housing, the machine will operate and turn off the potentially dangerous device.
Or you can make grounding yourself - drive a couple of crowbars deep into the ground, pour it with a very salty solution and connect the grounding wire. If you connect it to the common zero at the input (before the RCD), then it will reliably protect against the appearance of a second PHASE in the sockets (described above) and the combustion of household equipment. If it is not possible to reach it to the common zero, for example in a private house, then you should install a machine at your zero, as in a phase, otherwise, if the common zero in the switchboard burns out, the neighbors' current will go through your zero to a homemade grounding. And with a machine gun, support for neighbors will be provided only up to its limit and your zero will not suffer.
AFTERWORD
Well, it seems that I have described all the main common nuances of electricity not related to professional activities. Deeper details will require an even longer text. How clear and intelligible it turned out is to judge by those who are generally distant and incompetent in this topic (was :-).
Low bow and fond memory to the great physicists of Europe, who immortalized their names in units of measurement of electric current parameters: Alexandro Giuseppe Antonio Anastasio VOLTA - Italy (1745-1827); Andre Marie AMPERE - France (1775-1836); Georg Simon OM - Germany (1787-1854); James WATT - Scotland (1736-1819); Heinrich Rudolf HERZ - Germany (1857-1894); Michael Faraday - England (1791-1867).
POEM ABOUT ELECTRIC CURRENT:
Wait, don’t rush, let’s talk a little.
Wait, don’t rush, don’t rush the horses.
You and I are alone in the apartment this evening.
Electric current, electric current,
Similar in tension to the Middle East,
From the moment I saw the Bratsk hydroelectric power station,
My interest in you has arisen.
Electric current, electric current,
They say you can be cruel at times.
Your insidious bite can take your life,
Well, let it be, I’m still not afraid of you!
Electric current, electric current,
They claim that you are a stream of electrons,
And besides, idle people chatter,
That you are controlled by the cathode and anode.
I don't know what "anode" and "cathode" mean,
I already have a lot of worries,
But while you're flowing, electric current
The boiling water in my pan will not run out.
Igor Irtenev 1984
Nowadays it is impossible to imagine life without electricity. This is not only light and heaters, but also all electronic equipment, from the very first vacuum tubes to mobile phones and computers. Their work is described by a variety of, sometimes very complex, formulas. But even the most complex laws of electrical engineering and electronics are based on the laws of electrical engineering, which are studied in the subject “Theoretical Foundations of Electrical Engineering” (TOE) in institutes, technical schools and colleges.
Basic laws of electrical engineering
- Ohm's law
- Joule-Lenz law
- Kirchhoff's first law
Ohm's law- the study of TOE begins with this law and not a single electrician can do without it. It states that current is directly proportional to voltage and inversely proportional to resistance. This means that the higher the voltage applied to the resistor, motor, capacitor or coil (holding other conditions constant), the higher the current flowing through the circuit. Conversely, the higher the resistance, the lower the current.
Joule-Lenz law. Using this law, you can determine the amount of heat generated by a heater, cable, electric motor power or other types of work performed by electric current. This law states that the amount of heat generated when electric current flows through a conductor is directly proportional to the square of the current, the resistance of that conductor, and the time the current flows. Using this law, the actual power of electric motors is determined, and also on the basis of this law, the electric meter works, according to which we pay for the electricity consumed.
Kirchhoff's first law. It is used to calculate cables and circuit breakers when calculating power supply circuits. It states that the sum of currents entering any node is equal to the sum of currents leaving that node. In practice, one cable comes in from the power source, and one or more go out.
Kirchhoff's second law. Used when connecting several loads in series or a load and a long cable. It is also applicable when connected not from a stationary power source, but from a battery. It states that in a closed circuit the sum of all voltage drops and all emfs is 0.
Where to start studying electrical engineering
It is best to study electrical engineering in special courses or in educational institutions. In addition to the opportunity to communicate with teachers, you can take advantage of the educational institution’s facilities for practical classes. The educational institution also issues a document that will be required when applying for a job.
If you decide to study electrical engineering on your own or you need additional material for classes, then there are many sites where you can study and download the necessary materials to your computer or phone.
Video lessons
There are many videos on the Internet that help you master the basics of electrical engineering. All videos can be watched online or downloaded using special programs.
Electrician video tutorials- a lot of materials telling about various practical issues that a novice electrician may encounter, about the programs that he has to work with and about the equipment installed in residential premises.
Basics of electrical engineering theory- here are video lessons that clearly explain the basic laws of electrical engineering. The total duration of all lessons is about 3 hours.
- zero and phase, connection diagrams for light bulbs, switches, sockets. Types of tools for electrical installation;
- Types of materials for electrical installation, electrical circuit assembly;
- Switch connection and parallel connection;
- Installation of an electrical circuit with a two-button switch. Model of power supply for the premises;
- Model of power supply for a room with a switch. Safety Basics.
Books
The best advisor there was always a book. Previously, it was necessary to borrow a book from the library, from friends, or buy it. Nowadays on the Internet you can find and download a variety of books that a beginner or an experienced electrician needs. Unlike video tutorials, where you can watch how this or that action is performed, in a book you can keep it nearby while doing the work. The book may contain reference materials that will not fit into a video lesson (like in school - the teacher tells the lesson described in the textbook, and these forms of teaching complement each other).
There are sites with a large amount of electrical engineering literature on a variety of issues - from theory to reference materials. On all these sites, you can download the book you need to your computer and later read it from any device.
For example,
mexalib- various types of literature, including electrical engineering
books for electrician- this site has a lot of advice for the novice electrical engineer
electric specialist- site for beginner electricians and professionals
Electrician's Library- many different books mainly for professionals
Online textbooks
In addition, there are online textbooks on electrical engineering and electronics with an interactive table of contents on the Internet.
These are such as:
Electrician Basic Course- textbook on electrical engineering
Basic Concepts
Electronics for Beginners- initial course and basics of electronics
Safety precautions
The main thing when performing electrical work is compliance with safety precautions. If incorrect operation can lead to equipment failure, then failure to comply with safety precautions can lead to injury, disability or death.
Main rules- this means not touching live wires with bare hands, working with tools with insulated handles, and when turning off the power, posting a sign “do not turn on, people are working.” For a more detailed study of this issue, you need to take the book “Safety Rules for Electrical Installation and Adjustment Work.”
