Lessons for repairing household appliances on video. School for an electrician: everything about electrical engineering and electronics
There are many concepts that cannot be seen with your own eyes or touched with your hands. Most a shining 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, outlined in accessible language. 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 electric current consists in 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. Moving electric charge through cross section the 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 chemical composition 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, permanent transfer charge 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:
- Current strength: I = U/R (amps).
- Voltage: U = I x R (volts).
- 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 electrical resistance a conductor that 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 appliances consume a certain amount energy for 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
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 direction.
Ohm's law
For example, let's calculate the simplest chain, 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 leaving 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
Because the greater the current or voltage, the more 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 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.
That's what audiophiles do for their heavy-duty sound systems take thick ones copper wires with minimal resistance 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 TOE textbook from the network ( theoretical foundations electrical engineering) is better for intermediate educational institutions, everything is described there much simpler and more clearly - without going into higher mathematics.
Name: Radio electronics for beginners.
With this book the author intends to involve most interesting world radio electronics of new young fans of this creativity.
The material is presented from simple to complex. We used many years of teaching experience in a radio circle.
The book is intended for students in grades 5-11, college and technical school students, university students, as well as beginning radio amateurs.
The book “Radio Electronics for Beginners (and Not Only)” was written by a practical teacher who, from many years of experience, knows how to interest students to develop an interest in radio electronics.
The theoretical material in the book is presented in a form accessible to beginner radio amateurs for understanding physical processes analogies from mechanics and hydraulics are used, with which they are often encountered in life.
Designs recommended for self-made, taken from a course that the author has been teaching in a radio circle for many years. The author of the book hopes that the authors of the articles used in the book will react favorably to this approach. The recommended designs are selected in such a way that every radio amateur can test his knowledge in practice. If in a design proposed for manufacture a radio amateur finds elements unfamiliar to himself (transistors, microcircuits, etc.), he can turn to the corresponding chapter of the book, where, as a rule, he can find the answer to his question.
Introduction
Chapter 1. Electrical and radio engineering materials.
Soldering and Electrical Installation Basics
1.1.Metals
1.1.1.Editing sheet material
1.1.2. Sheet metal bending
1.1.3.Bending sheet duralumin
1.1.4.Metal cutting
1.1.5.Simple drilling rules
1.1.6. “Jacket” for the drill
1.1.7.Instead of a drill - a file
1.1.8.Dangers when drilling
1.1.9.Threads in holes
1.1.10.Homemade taps for threading
1.1.11.Cleaning contaminated surfaces
1.1.12. File care
1.1.13.Inscriptions on metal
1.1.14. Compatible and incompatible pairs of metals
1.2.Insulation materials
1.2.1.Areas of application
1.2.2.Working with insulating materials
1.3.Working with wood
1.3.1.Coating with epoxy glue
1.3.2.How to refresh products and parts made of light wood
1.3.3. Repair of cracks
1.4.Magnetic materials
1.5.Wires
1.5.1.Winding wires
1.5.1.1.Copper winding wires
1.5.1.2.High-frequency winding wires (Litz wires)
1.5.1.3.High resistance winding wires (manganin, constantan, nichrome)
1.5.2.Installation wires
1.6. Soldering and electrical installation basics
1.6.1. Soldering iron device
1.6.2. Soldering iron repair
1.6.3.Method of teaching soldering
1.6.4.Solders and fluxes
1.7.Useful tips
1.7.1. Soldering aluminum
1.7.2. Soldering nichrome
1.7.3. Tinning wires in enamel insulation
1.7.4.Instead of solder - glue
1.7.5. Litz wire
1.7.6. Varnish for painting rations
1.7.7. Protection of decals
Chapter 2. Direct electric current
2.1. DC electrical circuit
2.2. Electric current and voltage
2.3. Ohm's law. wire resistance
2.4.Serial and parallel connection of resistors
2.5.Measuring current, voltage and resistance
2.6.Electric current power
2.7. For self-production
2.7.1. Milliamometer
2.8.Helpful tips
2.8.1. Measuring voltages with a voltmeter with low input resistance
2.8.2. Measuring DC voltages with a milliammeter
2.8.3. Measuring current with a low-resistance voltmeter
2.8.4. Measuring small resistances with a milliammeter
2.8.5. Measuring resistance with a voltmeter
2.8.6. Two ways to measure the resistance and current of the total deviation of a microammeter using two constant resistors
2.8.7. What can a battery do?
2.9.Tasks
Chapter 3. Alternating Current
3.1. Alternating current of sinusoidal shape, obtaining alternating current, basic parameters
3.2. AC electrical circuit. Circuit elements
3.2.1. Capacitor as a storage device electrical energy
3.2.2. The capacitor "does not pass" D.C.
3.2.3. Capacitor resistance alternating current depends on its capacity and current frequency
3.2.4. The current strength leads the voltage across the capacitor by an angle p/2
3.2.5. The inductor has inductive reactance, which is also called reactive
3.2.6. Series and parallel connection of inductors
3.2.7. Inductor as a magnetic energy storage device
3.2.8. The current lags behind the voltage on the inductor by an angle p/2
3.2.9. On active resistance(on a resistor) current and voltage are in phase
3.3. Integrating and differentiating chains
3.4. Series oscillating circuit
3.5. For self-production
3.5.1.Color and music console
3.5.2. Amplifier audio frequency"electronic ear"
3.5.3. Electronic siren with amplifier
3.5.4.When the mains voltage is unstable
3.5.5. Thyristor regulator voltage
3.5.6. Two options for turning on lamps daylight
3.6. Useful tips
3.6.1. Determining the purpose of the windings of a network transformer
3.6.2. Determination of the number of turns of windings of a network transformer
3.6.3. Finding the winding with a large number turns
3.6.4. The electric motor will become stronger
3.6.5. Device for magnetizing magnets
3.6.6. How to demagnetize a tool
3.7.Tasks
Chapter 4. Semiconductor devices
4.1. Semiconductor diodes
4.2.1. Recommendations for the use of diodes
4.2.2. Zener diodes -
4.3. Bipolar transistors
4.3.1. General information
4.3.2. Transistor connection circuits
4.3.3.Basic parameters of transistors
4.3.4.Static voltage-voltage of the transistor
4.3.5. Analysis of amplifier stages
4.4.Field-effect transistors
4.4.1. Basic parameters of field-effect transistors
4.4.2. Maximum allowed parameters
4.4.3. Current-voltage characteristics PT
4.4.4. Recommendations for the use of PT
4.5. Thyristors
4.4.1.Basic parameters of thyristors
4.6. For self-production
4.6.1. Thyristor tester
4.6.2. Universal voltmeter
4.6.3. Radioactivity indicator
4.6.4. Probe for testing unijunction transistors
4.7. Useful tips. Simple experiments with diodes and zener diodes
4.7.1. How to remove the current-voltage characteristic of a diode? (Fig. 4.39)
4.7.2. Power regulator on one diode (Fig. 4.40)
4.7.3. Controlling a chandelier via two wires (Fig. 4.41)
4.7.4. The simplest generator noise (Fig. 4.42)
4.7.5. Receipt rectangular pulses from sinusoidal voltage (Fig. 4.43)
4.7.6. Zener diode - limiter DC voltage(Fig. 4.44)
4.7.7. How to “stretch” the voltmeter scale (Fig. 4.45)
4.7.8. Connecting a cassette recorder or receiver to a car network (Fig. 4.46)
4.7.9. Transistor - variable resistor(Fig. 4.47)
4.7.10. Transistor as a zener diode (Fig. 4.48)
4.7.11. Transistor as a rectifying diode (Fig. 4.49)
4.7.12. Device for thermal testing of transistors (Fig. 4.50)
4.7.13. Determination of transistor pinout (Fig. 4.51)
4.7. Tasks
Chapter 5. Radio Power electronic devices from AC mains
5.1.Single-phase rectifiers
5.2.Smoothing filters
5.2.1. Capacitive filters
5.2.2. L-shaped filters
5.3. External characteristics of rectifiers
5.4.Voltage stabilizers
5.4.1. Parametric voltage stabilizers
5.5. For self-production
5.5.1.Attached machine to the power supply
5.5.2. Stabilizer in adapter
5.5.3. Electroshock protection
5.5.4. Shaper bipolar voltages }