Without some basic knowledge about electricity, it is difficult to imagine how electrical appliances work, why they work at all, why you need to plug in the TV to make it work, and why a flashlight only needs a small battery to shine in the dark.
And so we will understand everything in order.
Electricity
Electricity is a natural phenomenon that confirms the existence, interaction and movement of electric charges. Electricity was first discovered back in the 7th century BC. Greek philosopher Thales. Thales noticed that if a piece of amber is rubbed on wool, it begins to attract light objects. Amber in ancient Greek is electron.
This is how I imagine Thales sitting, rubbing a piece of amber on his himation (this is a woolen outerwear among the ancient Greeks), and then looks with a puzzled look as hair, scraps of thread, feathers and scraps of paper are attracted to the amber.
This phenomenon is called static electricity. You can repeat this experience. To do this, rub thoroughly woolen fabric a regular plastic ruler and hold it to the small pieces of paper.
It should be noted that this phenomenon has not been studied for a long time. And only in 1600, in his essay “On the Magnet, Magnetic Bodies and the Great Magnet - the Earth,” the English naturalist William Gilbert introduced the term electricity. In his work, he described his experiments with electrified objects, and also established that other substances can become electrified.
Then, for three centuries, the most advanced scientists in the world researched electricity, wrote treatises, formulated laws, invented electrical machines, and only in 1897 Joseph Thomson discovered the first material carrier of electricity - the electron, a particle that makes electrical processes in substances possible.
Electron– this is an elementary particle, has a negative charge approximately equal to -1.602·10 -19 Cl (Pendant). Denoted e or e -.
Voltage
To make charged particles move from one pole to another, it is necessary to create between the poles potential difference or - Voltage. Voltage unit – Volt (IN or V). In formulas and calculations, voltage is denoted by the letter V . To obtain a voltage of 1 V, you need to transfer a charge of 1 C between the poles, while doing 1 J (Joule) of work.
For clarity, imagine a water tank located at a certain height. A pipe comes out of the tank. Water under natural pressure leaves the tank through a pipe. Let's agree that water is electric charge, the height of the water column (pressure) is voltage, and the speed of water flow is electricity.
Thus, the more water in the tank, the higher the pressure. Similarly from an electrical point of view, the greater the charge, the higher the voltage.
Let's start draining the water, the pressure will decrease. Those. The charge level drops - the voltage decreases. This phenomenon can be observed in a flashlight; the light bulb becomes dimmer as the batteries run out. Please note that the lower the water pressure (voltage), the lower the water flow (current).
Electricity
Electricity is a physical process of directed movement of charged particles under the influence of an electromagnetic field from one pole of a closed circuit electrical circuit to another. Charge-carrying particles can include electrons, protons, ions and holes. Without a closed circuit, no current is possible. Particles capable of carrying electrical charges do not exist in all substances; those in which they exist are called conductors And semiconductors. And substances in which there are no such particles - dielectrics.
Current unit – Ampere (A). In formulas and calculations, current strength is indicated by the letter I . A current of 1 Ampere is generated when a charge of 1 Coulomb (6.241·10 18 electrons) passes through a point in an electrical circuit in 1 second.
Let's look again at our water-electricity analogy. Only now let’s take two tanks and fill them with an equal amount of water. The difference between the tanks is the diameter of the outlet pipe.
Let's open the taps and make sure that the flow of water from the left tank is greater (the diameter of the pipe is larger) than from the right. This experience is clear evidence of the dependence of flow speed on pipe diameter. Now let's try to equalize the two flows. To do this, add water (charge) to the right tank. This will give more pressure(voltage) and will increase the flow rate (current). In an electrical circuit, the pipe diameter is played by resistance.
The experiments carried out clearly demonstrate the relationship between voltage, current And resistance. We'll talk more about resistance a little later, but now a few more words about the properties electric current.
If the voltage does not change its polarity, plus to minus, and the current flows in one direction, then this is D.C. and correspondingly constant pressure. If the voltage source changes its polarity and the current flows first in one direction, then in the other, this is already alternating current And AC voltage. Maximum and minimum values (indicated on the graph as Io ) - This amplitude or peak current values. In home sockets, the voltage changes its polarity 50 times per second, i.e. the current oscillates here and there, it turns out that the frequency of these oscillations is 50 Hertz, or 50 Hz for short. In some countries, for example in the USA, the frequency is 60 Hz.
Resistance
Electrical resistance – physical quantity, which determines the property of a conductor to impede (resist) the passage of current. Resistance unit – Ohm(denoted Ohm or the Greek letter omega Ω ). In formulas and calculations, resistance is indicated by the letter R . A conductor has a resistance of 1 ohm to the poles of which a voltage of 1 V is applied and a current of 1 A flows.
Conductors conduct current differently. Their conductivity depends, first of all, on the material of the conductor, as well as on the cross-section and length. The larger the cross section, the higher the conductivity, but the longer the length, the lower the conductivity. Resistance is the inverse concept of conductivity.
On the example of a plumbing model, the resistance can be represented as the diameter of the pipe. The smaller it is, the worse the conductivity and the higher the resistance.
The resistance of the conductor is manifested, for example, in the heating of the conductor when current flows in it. Moreover, the greater the current and the smaller the cross-section of the conductor, the stronger the heating.
Power
Electric power is a physical quantity that determines the rate of electricity conversion. For example, you have heard more than once: “a light bulb is so many watts.” This is the power consumed by the light bulb per unit of time during operation, i.e. converting one type of energy into another at a certain speed.
Sources of electricity, such as generators, are also characterized by power, but already generated per unit of time.
Power unit – Watt(denoted W or W). In formulas and calculations, power is indicated by the letter P . For alternating current circuits the term is used Full power , unit - Volt-amps (VA or V·A), denoted by the letter S .
And finally about Electric circuit. This circuit is a certain set of electrical components capable of conducting electric current and interconnected accordingly.
What we see in this image is a basic electrical device (flashlight). under tension U(B) a source of electricity (batteries) through conductors and other components with different resistances 4.61 (244 Votes)
The unit of voltage is named volt (V) in honor of the Italian scientist Alessandro Volta, who created the first galvanic cell.
The unit of voltage is taken as the voltage at the ends of the conductor, in which the work of moving electric charge in 1 C along this conductor is equal to 1 J.
1 V = 1 J / C
In addition to the volt, submultiples and multiples of it are used: millivolt (mV) and kilovolt (kV).
1 mV = 0.001 V;
1 kV = 1000 V.
High (large) voltage is life-threatening. Assume that the voltage between one wire high voltage line transmission and ground 100,000 V. If this wire is connected by some conductor to the ground, then when an electric charge of 1 C passes through it, work will be done equal to 100,000 J. Approximately the same work will be done by a load weighing 1000 kg when falling from a height 10 m. It can cause great destruction. This example shows why high voltage current is so dangerous.
Volta Alessandro (1745-1827)
The Italian physicist, one of the founders of the doctrine of electric current, created the first galvanic cell.
But caution must also be observed when working with lower voltages. Depending on the conditions, even a few tens of volts can be dangerous. For indoor work, a voltage of no more than 42 V is considered safe.
Galvanic cells create low voltage. Therefore, the lighting network uses electric current from generators that create voltages of 127 and 220 V, i.e., generating significantly more energy.
Questions
- What is the unit of voltage?
- What voltage is used in the lighting network?
- What is the voltage at the poles of a dry cell and an acid battery?
- What units of voltage, other than the volt, are used in practice?
Hello everyone, Vladimir Vasiliev is in touch with you again. New Year's celebrations are coming to an end, which means we need to prepare for everyday work, and congratulations to you, dear friends! Heh, just don't get upset and depressed, you need to think positively.
So, during these New Year holidays, I was once thinking about the audience of my blog: “Who is he? Who is the visitor to my blog that comes to read my posts every day?” Maybe this savvy specialist came in out of curiosity to read what I scribbled here? Or maybe it was some doctor of radio engineering who came in to see how to solder a multivibrator circuit? 🙂
You know, all this is unlikely, because for an experienced specialist all this is already a passed stage and most likely everything is no longer so interesting and they themselves have a mustache. They may be interested only out of idle curiosity, of course I am very pleased and I welcome everyone with open arms.
So I came to the conclusion that the main contingent of my blog and most amateur radio sites are beginners and amateurs scouring the Internet in search of useful information. So why the hell do I have so little of it? Will be sick soon so do not miss!
I remember myself when I was looking on the Internet for some simple scheme to start with, but something always didn’t fit, something seemed abstruse. I lacked the basics, such that I could begin to understand the topic that interested me, from simple to complex.
By the way, the first book that really helped me, from reading which understanding really began to come, was the book “The Art of Circuit Design” by P. Horowitz, W. Hill. I wrote about it in, and you can download the book there. So, if you are a beginner, be sure to download it and let it become your reference book.
What is voltage and current?
By the way, what exactly are electric current and voltage? I think that no one really knows, because to know it you have to at least see it. Who can see the current running through the wires?
Yes, no one, humanity has not yet achieved such technologies to personally observe the movements of electric charges. All that we see in textbooks and scientific works is some kind of abstraction created as a result of numerous observations.
Well, okay, we can talk a lot about this... So let's try to figure out what electric current and voltage are. I will not write definitions; definitions do not give the very understanding of the essence. If interested, take any physics textbook.
Since we do not see the electric current and all the processes occurring in the conductor, then we will try to create an analogy.
And traditionally, the electric current flowing in a conductor is compared to water running through pipes. In our analogy, water is an electric current. Water runs through the pipes at a certain speed, the speed is the current strength, measured in amperes. Well, pipes are a conductor in themselves.
Okay, we imagined electric current, but what is voltage? Let's help now.
The water in the pipe, in the absence of any forces (gravity, pressure), will not flow; it will rest like any other liquid poured onto the floor. So this force, or more precisely, energy in our plumbing analogy, will be the same tension.
But what happens to the water running from a reservoir located high above the ground? Water rushes in a stormy stream from the reservoir to the surface of the earth, driven by gravity. And the higher the tank is located from the ground, the faster water flows out of the hose. Do you understand what I'm talking about?
The higher the tank, the greater the force (read voltage) on the water. And so more speed water flow (read current strength). Now it becomes clear and a colorful picture begins to form in my head.
The concept of potential, potential difference
Closely related to the concept of electric current voltage is the concept of “potential”, or “potential difference”. Okay, back to our plumbing analogy.
Our tank is located on a hill, which allows water to flow down the pipe freely. Since the water tank is at a height, the potential of this point will be higher or more positive than that at ground level. See what happens?
We have two points with different potentials, more precisely different sizes potential.
It turns out that in order for electric current to flow through a wire, the potentials must not be equal. Current flows from a point of higher potential to a point of lower potential.
Remember this expression that current runs from plus to minus. So this is all the same. Plus is a more positive potential and minus is more negative.
By the way, do you want a question for backfilling? What will happen to the current if the potentials change places periodically?
Then we will observe how the electric current changes its direction to the opposite each time the potentials change. This will turn out to be alternating current. But we won’t consider it for now, so that a clear understanding of the processes can form in our heads.
Voltage measurement
To measure voltage, a voltmeter is used, although multimeters are now the most popular. A multimeter is a combined device that contains a lot of things. I wrote about it and told how to use it.
A voltmeter is just a device that measures the potential difference between two points. The voltage (potential difference) at any point in the circuit is usually measured relative to ZERO or GROUND or MASS or MINUS of the battery. It doesn’t matter, the main thing is that it should be the point with the lowest potential in the entire circuit.
So to measure the voltage direct current between two points, we do the following. The black (negative) probe of the voltmeter is stuck into the point where we can presumably observe a point with a lower potential (ZERO). We stick the red probe (positive) into the point whose potential is interesting to us.
And the result of the measurement will be the numerical value of the potential difference, or in other words, voltage.
Current measurement
Unlike voltage, which is measured at two points, current is measured at one point. Since the current strength (or they simply say current), according to our analogy, is the speed of water flow, this speed needs to be measured at only one point.
We need to cut the water pipe and insert a meter into the gap that will count liters and minutes. Something like this.
Similarly, if we return to the real world of our electrical model, we get the same thing. To measure the amount of electric current, we need to connect a simple device - an ammeter - to the open circuit of the electrical circuit. An ammeter is also included in the multimeter. You can also read at.
The multimeter probes need to be switched to current measurement mode. Then we cut our conductor and connect the pieces of wire to the multimeter and voila - the current value will be shown on the multimeter screen.
Well, dear friends, I think we didn’t waste our time. Having become familiar with our plumbing models, a puzzle began to take shape in my head and an understanding began to form.
Well, let's try to check it using Ohm's law.
- I - current measured in Amperes (A);
- U-voltage measured in Volts (V);
- R-resistance measured in Ohms (Ohm)
Ohm told us that electric current is directly proportional to voltage and inversely proportional to resistance.
I didn’t talk about resistance today, but I think you understand. The resistance to electric current is the material of the conductor. In our plumbing system, resistance to the flow of water is provided by rusty pipes clogged with rust and other things. 🙂
Thus, Ohm's law works in all its glory, both for the plumbing system and for the electrical one. Maybe I should go into plumbing, there are a lot of similarities. 🙂
The higher the water tank is raised, the faster the water will flow through the pipes. But if the pipes are dirty, the speed will be lower. The greater the resistance to water, the slower it will flow. If there is a blockage, then the water may rise altogether.
Well, for electricity. The magnitude of the current depends directly on the voltage (potential difference), and inversely depends on the resistance.
The higher the voltage, the greater the current, but the greater the resistance, the less the current. The voltage may be very high, but the current may not flow due to a break. And a break is the same as if, instead of a metal conductor, we connected a conductor made of air, and the air simply has a gigantic resistance. This is where the current stops.
Well, dear friends, now it’s time to wrap up, it seems like I’ve said everything I wanted to say in this article. If you have any questions please ask in the comments. There will be more to come, I plan to write a series of tutorials, so do not miss…
I wish you good luck, success and see you soon!
With n/a Vladimir Vasiliev.
P.S. Friends, be sure to subscribe to updates! By subscribing you will receive new content directly to your inbox! And by the way, each subscriber will receive a useful gift!
Constructor ZNATOK 320-Znat "320 schemes" is a tool that will allow you to gain knowledge in the field of electronics and electrical engineering and also gain an understanding of the processes occurring in conductors.
The constructor is a set of full-fledged radio components with special. constructive, allowing their installation without the help of a soldering iron. Radio components are mounted on a special board - a base, which ultimately makes it possible to obtain fully functional radio structures.
Using this constructor, you can assemble up to 320 different circuits, for the construction of which there is a detailed and colorful manual. And if you connect your imagination to this creative process, you can get countless different radio designs and learn to analyze their work. I consider this experience very important and for many it can be invaluable.
Here are some examples of what you can do with this constructor:
Flying propeller;
A lamp turned on by clapping your hands or a jet of air;
Controlled sounds star wars, fire truck or ambulance;
Musical fan;
Electric light gun;
Learning Morse code;
Lie detector;
Automatic street lamp;
Megaphone;
Radio station;
Electronic metronome;
Radio receivers, including FM range;
A device that reminds of the onset of darkness or dawn;
Alarm that the child is wet;
Security alarm;
Musical door lock;
Lamps in parallel and series connection;
Resistor as current limiter;
Capacitor charge and discharge;
Conductivity tester;
Amplifying effect of the transistor;
Darlington circuit.
P.S. We have a kind of redneck meter here - the greedy one will not notice the social button, but the generous one will share it with friends. 🙂
One of the physical quantities that was introduced to characterize the action electric field, is the voltage. The electric field, exerting a force on charged particles, sets them in motion and creates an electric current. When moving charges, work is done, which leads to a change in energy.
In what units is voltage measured?
The ratio of the work done by an arbitrary electric field when moving a positive charge from one point of the field to another to the amount of charge is called the voltage between these points:
$ U = ( A\over q ) $ (1)
U- voltage,
A- work, J,
q- charge, Cl.
This means that the work done by the electric field when moving a charge is equal to the product of voltage U between points per charge q:
$ A = ( q*U ) $ (2)
Rice. 1. The work of the electric field to move charges.
When the charge value is equal to 1 C, the equality $ U = A $ will be satisfied.
The unit of measurement for voltage is called the volt. In short writing, it is written with a capital letter V. The unit received its name in honor of the Italian scientist Alessandro Volta (1745-1827), who made a significant contribution to understanding the nature of electrical phenomena.
From considerations of the dimensions of quantities and formula (1), it follows that:
$$ [V] = ( [J]\over ) $$
Thus, a unit of voltage (1 Volt) is the voltage on a section of a circuit or at the ends of a conductor at which work is done to move an electric charge of 1 C (1 coulomb) equal to 1 J (1 Joule).
Multiples of Voltage Units
The actual values of the measured voltages can be tens of thousands of times greater or less than one volt. Therefore, for the convenience of recording (fixation), the following multiple and submultiple units were additionally introduced:
- 1 nanovolt - 1 nV = 10 -9 V;
- 1 microvolt - 1 µV = 10 -6 V;
- 1 millivolt - 1 mV = 10 -3 V;
- 1 kilovolt - 1 kV=10 3 V;
- 1 megavolt - 1 MV=10 6 V.
It must be remembered that high voltage poses a great danger to human health. A safe value for the human body is considered to be a voltage of 42 V under normal conditions and 12 V in conditions with increased danger (humidity, metal floors, high temperatures).
How is voltage measured?
Voltage is measured using an instrument called a voltmeter. Different models of voltmeters may differ in appearance from each other, but what they have in common is the operating principle based on the electromagnetic action of current. The Latin letter V is used to designate a device on electrical diagrams and on the measuring scales of voltmeters.
Rice. 2. Designation of a voltmeter and connection diagram of a voltmeter for measuring voltage.
When taking measurements, the following points must be taken into account:
- Voltmeters for measuring DC voltage are different from voltmeters designed for measuring AC voltage. Voltmeters for measuring direct voltages must have a “—” sign on the measuring scale, and for alternating voltage a “~” sign. IN Lately designation using letter abbreviations is often used English alphabet AC/DC (Alternative Current - alternating current, Direct Current - direct current);
- The terminals of voltmeters for constant voltage are marked with “+” and “—” signs or highlighted in color (plus - red, minus - blue). When taking measurements, polarity must be observed, otherwise the indicator needle will deviate in the other direction;
- The voltmeter is always connected in parallel to the section of the circuit where measurements are made;
- It is recommended to first install all the elements of the electrical circuit, and connect the voltmeter at the very end.
Rice. 3. Examples of various voltmeters
All measuring instruments should not influence the measurement result, that is, they should have a minimum measurement error. To meet this requirement, voltmeters have a very large input impedance, so the current flowing through them is much less than the current in the measured section of the circuit. Then the voltage drop on the voltmeter becomes insignificant.
What have we learned?
So, we learned that voltage is a physical quantity equal to the work of moving a charge of 1 C in an electric field. Voltage is measured in units called volts. Voltmeters are used to measure voltage.
Test on the topic
Evaluation of the report
Average rating: 4.5. Total ratings received: 60.
Essentially, the term refers to potential difference, and the unit of voltage is the volt. Volt is the name of the scientist who laid the foundation for everything we now know about electricity. And this man's name was Alessandro.
But this is what concerns electric current, i.e. the one with the help of which our usual household electrical appliances operate. But there is also the concept of a mechanical parameter. This parameter is measured in pascals. But this is not about him now.
What is a volt equal to?
This parameter can be either constant or variable. It is alternating current that “flows” into apartments, buildings and structures, houses and organizations. Electrical voltage represents amplitude waves, indicated on graphs as a sine wave.
Alternating current is indicated in diagrams by the symbol “~”. And if we talk about what one volt is equal to, then we can say that this is an electrical action in a circuit where, when a charge equal to one coulomb (C) flows, work equal to one joule (J) is performed.
The standard formula by which it can be calculated is:
U = A:q, where U is exactly the desired value; "A" is the work that is performed electric field(in J), transferring charge, and “q” is precisely the charge itself, in coulombs.
If we talk about constant values, then they practically do not differ from variables (with the exception of the construction graph) and are produced from them, using a rectifying diode bridge. Diodes, without passing current to one side, seem to divide the sine wave, removing half-waves from it. As a result, instead of phase and zero, we get plus and minus, but the calculation remains in the same volts (V or V).
Voltage measurement
Previously, only an analog voltmeter was used to measure this parameter. Now on the shelves of electrical engineering stores there is a very wide range of similar devices already in digital design, as well as multimeters, both analog and digital, with the help of which the so-called voltage is measured. Such a device can measure not only the magnitude, but also the current strength, the resistance of the circuit, and it is even possible to check the capacitance of the capacitor or measure the temperature.
Of course, analog voltmeters and multimeters do not provide the same accuracy as digital ones, the display of which shows the voltage unit down to hundredths or thousandths.
When measuring this parameter, the voltmeter is connected to the circuit in parallel, i.e. if it is necessary to measure the value between phase and zero, the probes are applied one to the first wire, and the other to the second, in contrast to measuring current, where the device is connected in series to the circuit.
In circuit diagrams, a voltmeter is indicated by the letter V surrounded by a circle. Various types such devices measure, in addition to the volt, different units of voltage. In general, it is measured in the following units: millivolt, microvolt, kilovolt or megavolt.
Voltage value
The value of this parameter of electric current in our life is very high, because whether it corresponds to the required one depends on how brightly the incandescent lamps will burn in the apartment, and if compact fluorescent lamps are installed, then the question arises whether or not they will light at all. The durability of all lighting and household electrical appliances depends on its surges, and therefore having a voltmeter or multimeter at home, as well as the ability to use it, is becoming a necessity in our time.
