A constant electric current is the movement of particles with a charge in a certain direction. That is, its voltage or force (characterizing quantities) have the same value and direction. This is how direct current differs from alternating current. But let's consider everything in order.
The history of the emergence and "war of currents"
Direct current used to be called galvanic because it was discovered as a result of a galvanic reaction. I tried to transmit it through electric transmission lines. At that time, there were serious disputes between scientists on this issue. They even got the name "current wars". The question of choosing as the main, variable or permanent was decided. The “fight” was won by the variable species, since the permanent one suffers significant losses, transmitted at a distance. But it is not difficult to transform the variable form, this is how direct current differs from alternating current. Therefore, the latter is easy to transmit even over long distances.
Sources of direct electric current
Batteries or other devices can serve as sources, where it occurs through a chemical reaction.
These are generators, where it is obtained as a result and after that it is rectified due to the collector.
Application
In various devices, direct current is used quite often. For example, many household appliances, chargers and car generators work with it. Any portable device is powered by a source that generates a constant look.
On an industrial scale, it is used in engines and batteries. And in some countries they are equipped with high-voltage power lines.
In medicine, with the help of direct electric current, wellness procedures are carried out.
On the railway (for transport), both variable and permanent types are used.
Alternating current
Most often, however, they use it. Here, the average value of force and stress over a certain period are equal to zero. In magnitude and direction, it is constantly changing, and at regular intervals.
To cause an alternating current, generators are used in which during electromagnetic induction occurs. This is done using a magnet rotated in a cylinder (rotor) and a stator made in the form of a fixed core with a winding.
Alternating current is used in radio, television, telephony and many other systems due to the fact that its voltage and power can be converted without losing energy almost.
It is widely used in industry, as well as for lighting purposes.
It can be single-phase and multi-phase.
Which changes according to the sinusoidal law, is single-phase. It changes over a certain period of time (period) in magnitude and direction. AC frequency is the number of cycles per second.
In the second case, the three-phase version was most widely used. This is a system of three electrical circuits that have the same frequency and EMF, shifted in phase by 120 degrees. It is used to power electric motors, furnaces, lighting fixtures.
Mankind owes many developments in the field of electricity and their practical application, as well as the impact on high frequency alternating current, to the great scientist Nikola Tesla. Until now, not all of his works, which have remained to posterity, are known.
How does direct current differ from alternating current and what is its path from source to consumer?
So, a variable is a current that can change in direction and magnitude for a certain time. The parameters to which attention is paid are the frequency and voltage. In Russia, household electrical networks supply alternating current with a voltage of 220 V and a frequency of 50 Hz. The frequency of an alternating current is the number of changes in the direction of particles of a certain charge per second. It turns out that at 50 Hz it changes its direction fifty times, in which direct current differs from alternating current.
Its source is sockets to which household appliances are connected under various voltages.
Alternating current begins its movement from power stations, where there are powerful generators, from where it comes out with a voltage of 220 to 330 kV. Further passes into which are located near houses, businesses and other structures.
In the substation, the current enters under a voltage of 10 kV. There it is converted into a three-phase voltage of 380 V. Sometimes with this indicator, the current passes directly to objects (where powerful production is organized). But basically it is reduced to the usual 220 V in all houses.
transformation
It is clear that in the outlets we get alternating current. But often electrical appliances need a permanent look. For this purpose, special rectifiers are used. The process consists of the following steps:
- connecting a bridge with four diodes having the necessary power;
- connecting a filter or capacitor to the output from the bridge;
- connection of voltage stabilizers to reduce ripples.
The conversion can take place both from AC to DC, and vice versa. But the latter case will be much more difficult to implement. You will need inverters, which, among other things, are quite expensive.
Despite the fact that electricity has firmly entered our lives, the vast majority of users of this blessing of civilization do not even have a superficial understanding of what current is, not to mention how direct current differs from alternating current, what is the difference between them, and what is current in general . The first person to be shocked was Alessandro Volta, after which he devoted his whole life to this topic. Let us also pay attention to this topic in order to have a general idea of the nature of electricity.
Where does current come from and why is it different?
We will try to avoid complex physics, and will use the method of analogies and simplifications to consider this issue. But before that, let's recall the old joke about the exam, when an honest student pulled out a ticket "What is electric current."
Sorry professor, I was preparing, but I forgot - answered the honest student. - How could you! The professor rebuked him, You are the only person on Earth who knew this! (from)
This is a joke, of course, but there is a lot of truth in it. Therefore, we will not look for Nobel laurels, but simply figure it out, alternating current and direct current, what is the difference, and what is considered to be current sources.
As a basis, we will take the assumption that the current is not the movement of particles (although the movement of charged particles also transfers charge, and therefore creates currents), but the movement (transfer) of excess charge in a conductor from a point of large charge (potential) to a point of lower charge. An analogy is a reservoir, water always tends to occupy one level (equalize potentials). If you open a hole in the dam, the water will begin to flow downhill, there will be a direct current. The larger the hole, the more water will flow, the current will increase, as will the power, and the amount of work that this current is capable of doing. If the process is not controlled, the water will destroy the dam and immediately create a flood zone with a level surface. This is a short circuit with potential equalization, accompanied by great destruction.
Thus, direct current appears in the source (as a rule, due to chemical reactions), in which there is a potential difference at two points. The movement of charge from a higher "+" to a lower "-" equalizes the potential while the chemical reaction continues. The result of the full equalization of the potential, we know - "the battery of the village." This leads to an understanding of why direct and alternating voltage differ significantly in the stability of characteristics. Batteries (accumulators) consume charge, so the DC voltage decreases over time. To maintain it at the same level, additional converters are used. Initially, mankind decided for a long time how direct current differs from alternating current for widespread use, the so-called. "War of currents". It ended with the victory of alternating current, not only because there is less loss during transmission over a distance, but also generating direct current from alternating current turned out to be easier. Obviously, the direct current obtained in this way (without a consumable source) has much more stable characteristics. In fact, in this case, the AC and DC voltages are tightly coupled, and in time they depend only on the energy generation and the amount of consumption.
Thus, direct current by its nature is the occurrence of an uneven charge in the volume (chemical reaction), which can be redistributed with the help of wires, connecting a point of high and low charge (potential).
Let us dwell on such a definition as generally accepted. All other direct currents (not batteries and accumulators) are derived from an alternating current source. For example, in this picture, the blue wavy line is our direct current, as a result of alternating current conversion. 
Pay attention to the comments to the picture, "a large number of circuits and collector plates." If the converter is different, the picture will be different. 
The same blue current line is almost constant, but pulsating, remember this word. Here, by the way, pure direct current is the red line.
Relationship between magnetism and electricity
Now let's see how alternating current differs from direct current, which depends on the material. The most important thing - the occurrence of an alternating current does not depend on the reactions in the material. Working with galvanic (direct current), it was quickly established that conductors are attracted to each other like magnets. The consequence was the discovery that a magnetic field under certain conditions generates an electric current. That is, magnetism and electricity turned out to be an interconnected phenomenon with an inverse transformation. A magnet could give current to a conductor, and a current-carrying conductor could be a magnet. In this picture, the simulation of Faraday's experiments, which, in fact, discovered this phenomenon. 
Now the analogy for alternating current. We will have an attractive force as a magnet, and an hourglass with water as a current generator. On one half of the clock we will write “top”, on the other “bottom”. We turn our watch over and see how the water flows “down”, when all the water has flowed, we turn it over again and our water flows “up”. Despite the fact that we have current available, it changes direction twice in a full cycle. In science, it will look like this: the frequency of the current depends on the frequency of rotation of the generator in a magnetic field. Under certain conditions, we get a pure sine wave, or just an alternating current with different amplitudes.
Again! This is very important for understanding the difference between direct current and alternating current. In both analogies, the water flows "downhill". But in the case of direct current, the reservoir will empty sooner or later, and for alternating current, the clock will pour water for a very long time, it is in a closed volume. But at the same time, in both cases, the water flows downhill. True, in the case of alternating current, it flows half the time downhill, but up. In other words, the direction of movement of the alternating current is an algebraic value, that is, “+” and “-” continuously change places, while the direction of current movement remains unchanged. Try to think about and understand this difference. How fashionable it is to say online: "You understood this, now you know everything."
What causes a wide variety of currents
If you understand what is the difference between direct and alternating currents, a natural question arises - why are there so many of them, currents? Would choose one current as the standard, and everything would be the same.
But, as they say, “not all currents are equally useful”, by the way, let's think about which current is more dangerous: direct or alternating, if we roughly imagined not the nature of the current, but rather its features. A person is a collodion that conducts electricity well. A set of different elements in the water (we are 70% of the water, if anyone is not in the know). If a voltage is applied to such a collodion - an electric shock, then the particles inside us will begin to transfer charge. As it should be from a point of high potential to a point of low potential. The most dangerous thing is to stand on the ground, which is generally a point with an infinitely zero potential. In other words, we will transfer the entire current to the ground, that is, the difference in charges. So, with a constant direction of charge movement, the process of potential equalization in our body occurs smoothly. We are like sand passing water through us. And we can safely "absorb" a lot of water. With alternating current, the picture is slightly different - all our particles will “pull” here and there. The sand will not be able to calmly pass water, and the whole will be stirred up. Therefore, the answer to the question of which current is more dangerous, constant or variable, the answer is unequivocal - variable. For reference, the life-threatening threshold DC current is 300mA. For AC these values are frequency dependent and start at 35mA. At a current of 50 hertz 100mA. Agree, the difference of 3-10 times in itself answers the question: what is more dangerous? But this is not the main argument in choosing the current standard. Let's order everything that is taken into account when choosing the type of current:
- Delivery of current over long distances. The direct current will be lost almost all;
- Transformation in heterogeneous electrical circuits with an indefinite level of consumption. For direct current, a practically unsolvable problem;
- Maintaining a constant voltage for alternating current is two orders of magnitude cheaper than for direct current;
- The conversion of electrical energy into mechanical force is much cheaper in AC motors and mechanisms. Such motors have their drawbacks and in a number of areas cannot replace DC motors;
- For mass use, therefore, direct current has one advantage - it is safer for humans.
Hence the reasonable compromise that mankind has chosen. Not just one current, but the whole set of available transformations from generation, delivery to the consumer, distribution and use. We will not list everything, but we consider the main answer to the question of the article, “what is the difference between direct current and alternating current,” in one word - characteristics. This is probably the most correct answer for any domestic purposes. And to understand the standards, we propose to consider the main characteristics of these currents.
The main characteristics of the currents used today
If for direct current since the discovery the characteristics have remained generally unchanged, then with alternating currents everything is much more complicated. Look at this picture - a model of current flow in a three-phase system from generation to consumption 
From our point of view, it is a very illustrative model, on which it is clear how to remove one phase, two or three. At the same time, you can see how it gets to the consumer.
As a result, we have a generation chain, AC and DC voltage (currents) at the consumer stage. Accordingly, the farther from the consumer, the higher the currents and voltage. In fact, in our outlet, the simplest and weakest is single-phase alternating current, 220V with a fixed frequency of 50 Hz. Only an increase in frequency is capable of making the current high-frequency at this voltage. The simplest example is in your kitchen. Microwave printing converts simple current into high frequency, which actually helps to cook. By the way, let's answer the question about microwave power - this is just how much "ordinary" current it converts into high-frequency currents.
It is worth remembering that any transformation of currents is not "for nothing". To get alternating current, you need to rotate the shaft with something. To get a direct current from it, you have to dissipate part of the energy as heat. Even power transmission currents will have to be dissipated in the form of heat when delivered to the apartment using a transformer. That is, any change in the current parameters is accompanied by losses. And of course, losses are accompanied by the delivery of current to the consumer. This seemingly theoretical knowledge allows us to understand where our overpayments for energy come from, removing half of the questions why there are 100 rubles on the meter, and 115 on the receipt.
Let's get back to currents. We have mentioned everything, and we even know how direct current differs from alternating current, so let's recall what currents there are in general.
- D.C, the source is the physics of chemical reactions with a change in charge, can be obtained by converting alternating current. A variation is a pulsed current that changes its parameters over a wide range, but does not change the direction of movement.
- Alternating current. Can be single-phase, two-phase or three-phase. Standard or high frequency. Such a simple classification is sufficient.
Conclusion or each current has its own device
The photo shows a current generator at the Sayano-Shushenskaya HPP. And in this photo, the place of its installation. 
And this is just a light bulb. 
Isn't it true that the difference in scale is striking, although the first was created, including for the work of the second? If you think about this article, it becomes clear that the closer the device is to a person, the more often direct current is used in it. With the exception of DC motors and industrial applications, this is really a standard based precisely on the fact that we found out which current is more dangerous direct or alternating. The characteristics of domestic currents are based on the same principle, since alternating current 220V 50Hz is a compromise between danger and losses. The price of a compromise is protective automation: from a fuse to an RCD. Moving away from the person, we find ourselves in the zone of transient characteristics, where both currents and voltages are higher, and where the danger to humans is not taken into account, but attention is paid to safety - the zone of industrial use of current. The furthest away from man, even in industry, is power transmission and generation. There is nothing for a mere mortal to do here - this is a zone of professionals and specialists who know how to control this power. But even with the domestic use of electricity, and of course when working with an electrician, understanding the basics of the nature of currents will never be superfluous.
What is the difference between AC and DC
The general concept of electric current can be expressed as the movement of various charged particles (electrons, ions) in a certain direction. And its value is characterized by the number of charged particles that have passed through the conductor in a certain period of time.
If the value of charged particles of 1 pendant passes through a certain section of the conductor in a time of 1 second, then we can talk about the strength of the current of 1 ampere flowing through the conductor. Thus, the number of amperes or current strength is determined. This is the general concept of current. Now consider the concept of alternating and direct current and their difference.
A constant electric current, by definition, is a current that flows in only one direction and does not change direction over time. Alternating current is characterized by the fact that it changes its direction and magnitude with time. If graphically the direct current is displayed as a straight line, then the alternating current flows through the conductor according to the sine law and is graphically displayed as a sinusoid.
Since the alternating current changes according to the law of a sinusoid, it has such parameters as the period of a full cycle, the time of which is indicated by the letter T. The frequency of the alternating current is the inverse of the period of a full cycle. The frequency of alternating current is expressed as the number of complete periods in a certain period of time (1 sec).
There are 50 such periods in our AC power network, which corresponds to a frequency of 50 Hz. F = 1/T, where the period for 50 Hz is 0.02 sec. F \u003d 1 / 0.02 \u003d 50 Hz. Alternating current is denoted by the English letters AC and the sign "~". Direct current has the designation DC and the sign "-". In addition, alternating current can be single-phase or multi-phase. Basically, a three-phase network is used.
Why is the voltage in the network alternating voltage, and not constant
Alternating current has many advantages over direct current. Low losses during the transmission of alternating current in power lines (TL) compared to direct current. Alternators are simple and cheap. When transmitting over long distances over power lines, high voltage reaches 330 thousand volts with a minimum current.
The lower the current in the power line, the lower the losses. Transmission of direct current over long distances will incur considerable losses. Also, high-voltage alternators are much simpler and cheaper. It is easy to convert alternating voltage to lower voltage through simple transformers.
Also, it is much cheaper to get DC voltage from AC than vice versa, using expensive DC-to-AC converters. Such converters have low efficiency and high losses. Double conversion is used along the AC transmission path.
First, it receives 220 - 330 kV from the generator, and transmits it over long distances to transformers that lower the high voltage to 10 KV, and then there are substations that lower the high voltage to 380 V. From these substations, electricity diverges among consumers and goes to houses and electrical panels apartment building.
Three phases of three-phase current shifted by 120 degrees
For a single-phase voltage, one sinusoid is characteristic, and for a three-phase voltage, three sinusoids, shifted by 120 degrees relative to each other. A three-phase network also has its advantages over single-phase networks. These are smaller dimensions of transformers, electric motors are also structurally smaller.
It is possible to change the direction of rotation of the rotor of an asynchronous electric motor. In a three-phase network, 2 voltages can be obtained - these are 380 V and 220 V, which are used to change the engine power and adjust the temperature of the heating elements. Using a three-phase voltage in lighting, flickering of fluorescent lamps can be eliminated, for which they are connected to different phases.
Direct current is used in electronics and in all household appliances, as it is easily converted from alternating current by dividing it on a transformer to the desired value and further straightening. DC sources are accumulators, batteries, DC generators, LED panels. As you can see, there is a significant difference between AC and DC. Now we have learned - Why is alternating current flowing in our outlet, and not direct current?
Now it is impossible to imagine human civilization without electricity. TVs, computers, refrigerators, hair dryers, washing machines - all household appliances work on it. Not to mention industry and big corporations. The main source of energy for electrical receivers is alternating current. And what is it? What are its parameters and characteristics? What is the difference between direct and alternating current? Few people know the answers to these questions.
Variable versus constant
At the end of the nineteenth century, thanks to discoveries in the field of electromagnetism, a dispute arose over what kind of current should be used to satisfy human needs. How did it all start? Thomas Edison founded his company in 1878, which later became the famous General Electric. The company quickly became rich and gained the confidence of investors and ordinary citizens of the United States of America, as several hundred direct current power plants were built throughout the country. The merit of Edison is in the invention of the three-wire system. Direct current worked remarkably well with the first electric motors and incandescent lamps. These were in fact the only power receivers at that time. The meter, which was also invented by Edison, operated exclusively on direct current. However, Edison's growing company was opposed by competitive corporations and inventors who wanted to oppose direct current to alternating current.
Disadvantages of Edison's Invention
George Westinghouse, an engineer and businessman, noticed the weak link in Edison's patent - the huge losses in the conductors. However, he failed to develop a design that could compete with this invention. What is the disadvantage of Edison direct current? The main problem is the transmission of electricity over distances. And since with its increase, the resistance of the conductors also increases, this means that power losses will also increase. To lower this level, it is necessary either to increase the voltage, and this will lead to a decrease in the strength of the current itself, or to thicken the wire (that is, to reduce the resistance of the conductor). There were no ways to effectively increase the DC voltage at that time, so Edison's power plants kept the voltage close to two hundred volts. Unfortunately, the power flows transmitted in this way could not meet the needs of industrial enterprises. Direct current could not guarantee the generation of electricity to powerful consumers who were at a considerable distance from the power plant. And it was too expensive to increase the thickness of the wires or build more stations.
AC vs DC
Thanks to the transformer developed in 1876 by engineer Pavel Yablochkov, it was very easy to change the voltage of alternating current, which made it possible to transmit it amazingly over hundreds and thousands of kilometers. However, at that time there were no motors that would run on alternating current. Accordingly, there were no generating stations and networks for transmission.
Inventions of Nikola Tesla
The undoubted advantage of permanent did not last long. Nikola Tesla, working as an engineer at the Edison company, realized that direct current cannot provide electricity to humanity. Already in 1887, Tesla received several patents for alternating current devices at once. A whole struggle for more efficient systems began. Tesla's main competitors were Thomson and Stanley. And in 1888, a Serbian engineer won a clear victory by providing a system capable of transporting electrical energy over distances of hundreds of miles. The young inventor was quickly taken in by Westinghouse. However, a confrontation immediately began between the companies of Edison and Westinghouse. Already in 1891, Tesla developed a three-phase alternating current system, which made it possible to win a tender for the construction of a huge power plant. Since then, alternating current has taken the unequivocal position of the leader. The standing one was losing ground on all fronts. Especially when rectifiers appeared that could convert alternating current to direct current, which became convenient for all receivers.
Definition of alternating current
An example of a simple generator
As the simplest source, a rectangular frame made of copper is used, which is fixed on an axis and rotates in a magnetic field using a belt drive. The ends of this frame are soldered to copper slip rings that slide over the brushes. The magnet creates a magnetic field evenly distributed in space. The density of magnetic lines of force here is the same in any part. The rotating frame intersects these lines and an alternating electromotive force (emf) is induced on its sides. With each turn, the direction of the total EMF is reversed, since the working sides of the frame per revolution pass through different poles of the magnet. Since the speed of crossing the lines of force changes, the magnitude of the electromotive force also becomes different. Therefore, if the frame is rotated uniformly, then the induced electromotive force will periodically change both in direction and magnitude, it can be measured using external instruments and, as a result, used to create an alternating current in external circuits.
sinusoidality
What it is? Alternating current is graphically characterized by a wavy curve - a sinusoid. Accordingly, EMF, current and voltage, which change according to this law, are called sinusoidal parameters. The curve is so named because it is an image of a trigonometric variable - the sine. It is the sinusoidal nature of alternating current that is the most common in all electrical engineering.
Parameters and characteristics
Alternating current is a phenomenon that is characterized by certain parameters. These include amplitude, frequency and period. The latter (denoted by the letter T) is the period of time during which the voltage, current or EMF completes a cycle of complete change. The faster the rotation of the rotor of the generator, the shorter the period. Frequency (f) refers to the number of complete cycles of current, voltage or EMF. It is measured in Hz (hertz) and denotes the number of periods in one second. Accordingly, the longer the period, the lower the frequency. The amplitude of such a phenomenon as alternating current is called its largest value. The amplitude of voltage, current or electromotive force is recorded in letters with the index "t" - U t I t, E t, respectively. Often, the effective value is referred to the parameters and characteristics of alternating current. Voltage, current or EMF, which acts in the circuit at every moment of time - an instantaneous value (marked with lowercase letters - i, u, e). However, it is difficult to evaluate the alternating current, the work done by it, the heat created by the instantaneous value, since it is constantly changing. Therefore, the current is used, which characterizes the strength of the direct current, which releases as much heat during the passage through the conductor as the alternating current does.
A long time ago, scientists invented electric current. The first invention was the permanent one. But later, while conducting experiments in his laboratory, Nikola Tesla invented alternating current. There were and are many differences between them, according to which one of them is used in low-current equipment, and the other has the ability to overcome various distances with little loss. But much depends on the magnitude of the currents.
AC and DC current: difference and features
The difference between alternating current and direct current can be understood based on the definitions. In order to better understand the principle of operation and features, you need to know the following factors.
Main differences:
- Movement of charged particles;
- Mode of production.
An alternating current is called such a current in which charged particles are able to change the direction of movement and magnitude at a certain time. The main parameters of alternating current include its voltage and frequency.
Currently, public electrical networks and various facilities use alternating current, with a certain voltage and frequency. These parameters are determined by the equipment and devices.
Note! In household electrical networks, a current of 220 volts and a clock frequency of 50 Hz is used.
The direction of motion and the frequency of charged particles in direct current are unchanged. This current is used to power various household devices, such as televisions and computers.
Due to the fact that alternating current is simpler and more economical in terms of production and transmission over various distances, it has become the basis for the electrification of objects. Alternating current is produced at various power plants, from which it is supplied to the consumer through conductors.
Direct current is obtained by converting alternating current or by chemical reactions (for example, an alkaline battery). For conversion, current transformers are used.
What voltage level is acceptable for a person: features
In order to know what values of electric current are permissible for a person, the corresponding tables have been compiled, which indicate the values \u200b\u200bof alternating and direct currents and time.
Parameters of exposure to electric current:
- Strength;
- Frequency;
- Time;
- relative humidity.
The allowable contact voltage and current that flow through the human body in various modes of electrical installations do not exceed the following values.
Alternating current 50 Hz, should be no more than 2.0 Volts and a current of 0.3 mA. Current with a frequency of 400 Hz, a voltage of 3.0 Volts and a current strength of 0.4 mA. DC voltage 8 and current 1 mA. Safe exposure to current with such indicators, up to 10 minutes.
Note! If electrical work is carried out at elevated temperatures and high relative humidity, these values are reduced by a factor of three.
In electrical installations with voltages up to 100 volts, which are deafly grounded, or the neutral is isolated, the safe touch currents are as follows.
Alternating current 50 Hz with voltage spread from 550 to 20 Volts and current strength from 650 to 6 mA, alternating current 400 Hz with voltage from 650 to 36 Volts, and direct current from 650 to 40 Volts, should not affect the human body within the limits of 0.01 to 1 second.
Dangerous alternating current for humans
It is believed that for human life, alternating electric current is the most dangerous. But this is on condition, if you do not go into details. Much depends on various quantities and factors.
Factors affecting the hazardous impact:
- duration of contact;
- The path of the electric current;
- Current and voltage;
- What is the resistance of the body.
According to the rules of the PUE, the most dangerous current for a person is an alternating current with a frequency that varies from 50 to 500 Hz.
It is worth noting that, provided that the current strength does not exceed 9 mA, then anyone can free himself from the current-carrying part of the electrical installation.
If this value is exceeded, then in order to get rid of the effects of electric current, a person needs external help. This is due to the fact that the alternating current is much more capable of excitating nerve endings and causing involuntary muscle spasms.
For example, when touching the live part of the device with the inside of the hand, the muscle cramp will tighten the fist more strongly over time.
Why is alternating current more dangerous? With the same values of the current strength, the alternating one affects the body several times stronger.
Since alternating current affects the nerve endings and muscles, it is worth understanding that this also affects the functioning of the heart muscle. From which it follows that in contact with alternating current, the risk of death increases.
An important indicator is the resistance of the human body. But when struck by alternating current with high frequencies, the resistance of the body is significantly reduced.
How much direct current is dangerous for a person
Dangerous for humans, can be direct current. Of course variable, ten times more dangerous. But if we consider currents in various quantities, then direct can be much more dangerous than alternating.
The impact of direct current on a person is divided:
- 1 threshold;
- 2 threshold;
- 3 threshold.
When exposed to the direct current of the first threshold (the current is palpable), the hands begin to tremble a little, and a slight tingling appears.
The second threshold (current not releasing), ranging from 5 to 7 mA, is the smallest value at which a person cannot free himself from the conductor on his own.
This current is considered not dangerous, since the resistance of the human body is higher than its values.
The third threshold (fibrillation), at values from 100 mA and above, the current strongly affects the body and internal organs. In this case, the current at these values can cause a chaotic contraction of the heart muscle and lead to its stop.
Other factors also influence the strength of the impact. For example, dry human skin has a resistance of 10 to 100 kOhm. But if the touch happened with a wet skin surface, then the resistance is significantly reduced.
