An electric current in a conductor arises under the influence of an electric field that causes free charged particles to come into directed motion. Create particle current - serious problem. To build such a device that will maintain the potential difference of the field for a long time in one state is a task, the solution of which turned out to be within the power of mankind only to late XVIII century.
First attempts
The first attempts to "accumulate electricity" for its further research and use were made in Holland. The German Ewald Jürgen von Kleist and the Dutchman Peter van Muschenbruk, who conducted their research in the town of Leiden, created the world's first capacitor, later called the "Leyden jar".
The accumulation of electric charge has already taken place under the action of mechanical friction. It was possible to use a discharge through a conductor for a certain, rather short, period of time.
The victory of the human mind over such an ephemeral substance as electricity turned out to be revolutionary.
Unfortunately, the discharge (the electric current created by the capacitor) lasted so short that it could not be created. In addition, the voltage given by the capacitor gradually decreases, which makes it impossible to obtain a continuous current.
It was necessary to look for another way.
First source
The experiments of the Italian Galvani on the study of "animal electricity" were an original attempt to find a natural source of current in nature. While hanging the legs of dissected frogs on metal hooks of an iron lattice, he drew attention to the characteristic reaction of nerve endings.
However, Galvani's findings were refuted by another Italian, Alessandro Volta. Interested in the possibility of obtaining electricity from animal organisms, he conducted a series of experiments with frogs. But his conclusion was complete opposite previous hypotheses.
Volta drew attention to the fact that a living organism is only an indicator of an electrical discharge. When the current passes, the muscles of the legs contract, indicating a potential difference. The source of the electric field was the contact of dissimilar metals. The farther apart they are in a series of chemical elements, the greater the effect.
Plates of dissimilar metals, lined with paper discs impregnated with an electrolyte solution, created the necessary potential difference for a long time. And let it be low (1.1 V), but the electric current could be investigated long time. The main thing is that the tension remained unchanged for just as long.
What's happening
Why is such an effect caused in sources called "galvanic cells"?
Two metal electrodes placed in a dielectric play different roles. One supplies electrons, the other accepts them. The redox reaction process leads to the appearance of an excess of electrons on one electrode, which is called the negative pole, and a deficiency on the second, we will denote it as the positive pole of the source.
In the simplest galvanic cells, oxidative reactions occur on one electrode, and reduction reactions occur on the other. Electrons come to the electrodes from the outside of the circuit. The electrolyte is the current conductor of the ions inside the source. The force of resistance governs the duration of the process.
Copper zinc element
It is interesting to consider the principle of operation of galvanic cells using the example of a copper-zinc galvanic cell, the action of which is due to the energy of zinc and copper sulfate. In this source, a copper plate is placed in a solution and a zinc electrode is immersed in a solution of zinc sulfate. The solutions are separated by a porous spacer to avoid mixing, but they must be in contact.
If the circuit is closed, the surface layer of zinc is oxidized. In the process of interaction with the liquid, zinc atoms, having turned into ions, appear in the solution. Electrons are released at the electrode, which can take part in the generation of current.
Getting to the copper electrode, the electrons take part in the reduction reaction. From the solution, copper ions enter the surface layer; in the process of reduction, they turn into copper atoms, depositing on the copper plate.
To summarize what is happening: the process of operation of a galvanic cell is accompanied by the transfer of electrons from the reducing agent to the oxidizing agent along the outer part of the circuit. Reactions take place on both electrodes. An ion current flows inside the source.
Difficulties of use
In principle, any of the possible redox reactions can be used in batteries. But there are not so many substances capable of working in technically valuable elements. Moreover, many reactions require expensive substances.
Modern rechargeable batteries have a simpler structure. Two electrodes placed in one electrolyte fill the vessel - the battery case. Such design features simplify the structure and reduce the cost of batteries.
Any galvanic cell is capable of creating direct current.
The current resistance does not allow all the ions to reach the electrodes at the same time, so the element works for a long time. Chemical reactions of the formation of ions sooner or later stop, the element is discharged.
The source of current is of great importance.
A word about resistance
Usage electric current, undoubtedly brought scientific and technical progress on the new stage, gave him a giant boost. But the force of resistance to the flow of current gets in the way of such development.
On the one hand, electric current has invaluable properties used in everyday life and technology, on the other hand, there is significant opposition. Physics, as a science of nature, tries to establish a balance, to bring these circumstances into line.
Current resistance arises due to the interaction of electrically charged particles with the substance through which they move. Exclude this process in normal temperature conditions impossible.
Resistance
The current source and the resistance of the external part of the circuit are of a slightly different nature, but the same in these processes is the work done to move the charge.
The work itself depends only on the properties of the source and its content: the qualities of the electrodes and electrolyte, as well as for the external parts of the circuit, the resistance of which depends on the geometric parameters and chemical characteristics of the material. For example, the resistance of a metal wire increases with an increase in its length and decreases with an expansion of the cross-sectional area. When solving the problem of how to reduce resistance, physics recommends using specialized materials.
Current work
In accordance with the Joule-Lenz law, the amount of heat released in conductors is proportional to the resistance. If the amount of heat denote Q ext. , current strength I, its flow time t, then we get:
- Q int. = I 2 r t,
where r is the internal resistance of the current source.
In the entire circuit, including both its internal and external parts, the total amount of heat will be released, the formula of which is:
- Q total \u003d I 2 r t + I 2 R t \u003d I 2 (r + R) t,
It is known how resistance is denoted in physics: an external circuit (all elements except the source) has resistance R.
Ohm's law for a complete circuit
We take into account that the main work is done by external forces inside the current source. Its value is equal to the product of the charge carried by the field and the electromotive force of the source:
- q E = I 2 (r + R) t.
realizing that the charge is equal to the product current strength for the duration of its flow, we have:
- E = I (r + R).
In accordance with cause-and-effect relationships, Ohm's law has the form:
- I = E: (r + R).
in a closed circuit is directly proportional to source emf current and is inversely proportional to the total (total) resistance of the circuit.
Based on this pattern, it is possible to determine the internal resistance of the current source.
Discharge capacity of the source
The discharge capacity can also be attributed to the main characteristics of the sources. The maximum amount of electricity obtained during operation under certain conditions depends on the strength of the discharge current.
Ideally, when certain approximations are made, the discharge capacity can be considered constant.
For example, a standard battery with a potential difference of 1.5 V has a discharge capacity of 0.5 Ah. If the discharge current is 100mA, then it works for 5 hours.
Battery Charging Methods
Using the batteries causes them to discharge. charging of small-sized elements is carried out using a current whose strength value does not exceed one tenth of the source capacity.
Offered the following ways charging:
- use of a constant current for a specified time (about 16 hours with a current of 0.1 battery capacity);
- charging with a step-down current up to a given value of the potential difference;
- use of asymmetric currents;
- successive application of short pulses of charging and discharging, in which the time of the first exceeds the time of the second.
Practical work
The task is proposed: to determine the internal resistance of the current source and EMF.
To perform it, you need to stock up on a current source, an ammeter, a voltmeter, a slider rheostat, a key, a set of conductors.
Use will determine the internal resistance of the current source. To do this, you need to know its EMF, the value of the resistance of the rheostat.
The calculation formula for the current resistance in the outer part of the circuit can be determined from Ohm's law for the circuit section:
- I=U:R,
where I is the current strength in the outer part of the circuit, measured with an ammeter; U is the voltage across the external resistance.
To improve the accuracy, measurements are taken at least 5 times. What is it for? The voltage, resistance, current (more precisely, current strength) measured during the experiment are used further.
To determine the EMF of the current source, we use the fact that the voltage at its terminals with the key open is almost equal to the EMF.
We will assemble a circuit from a battery, a rheostat, an ammeter, a key connected in series. We connect a voltmeter to the terminals of the current source. Having opened the key, we take its readings.
The internal resistance, the formula of which is obtained from Ohm's law for a complete circuit, is determined by mathematical calculations:
- I = E: (r + R).
- r = E: I - U: I.
Measurements show that the internal resistance is much less than the external one.
The practical function of accumulators and batteries is widely used. Undisputed environmental Safety electric motors is beyond doubt, but creating a capacious, ergonomic battery is a problem of modern physics. Its solution will lead to a new round of development of automotive technology.
Small, light, high-capacity batteries are also essential in mobile electronic devices Oh. The amount of energy used in them is directly related to the performance of the devices.
At the ends of the conductor, and hence the current, it is necessary to have external forces of a non-electric nature, with the help of which the separation of electric charges occurs.
Third party forces any forces acting on electrically charged particles in a circuit are called, with the exception of electrostatic (i.e., Coulomb).
Third-party forces set in motion charged particles inside all current sources: in generators, at power plants, in galvanic cells, batteries, etc.
When the circuit is closed, it creates electric field in all conductors of the circuit. Inside the current source, the charges move under the action of external forces against the Coulomb forces (electrons move from a positively charged electrode to a negative one), and in the rest of the circuit they are driven by an electric field (see figure above).
In current sources, in the course of work on the separation of charged particles, a transformation occurs different types energy into electricity. According to the type of converted energy, the following types of electromotive force are distinguished:
- electrostatic- in an electrophore machine, in which mechanical energy is converted into electrical energy during friction;
- thermoelectric- in a thermoelement, the internal energy of a heated junction of two wires made of different metals is converted into electrical energy;
- photovoltaic— in a photocell. Here, light energy is converted into electrical energy: when certain substances are illuminated, for example, selenium, copper oxide (I), silicon, a loss of a negative electric charge is observed;
- chemical- in galvanic cells, batteries, and other sources in which chemical energy is converted into electrical energy.
Electromotive Force (EMF)- characteristic of current sources. The concept of EMF was introduced by G. Ohm in 1827 for circuits direct current. In 1857, Kirchhoff defined EMF as the work of external forces during the transfer of a unit electric charge along a closed circuit:
ɛ \u003d A st / q,
where ɛ - EMF of the current source, A st- the work of external forces, q is the amount of charge transferred.
The electromotive force is expressed in volts.
We can talk about the electromotive force in any part of the circuit. This is the specific work of external forces (the work of moving a unit charge) not in the entire circuit, but only in this area.
Internal resistance of the current source.
Let there be a simple closed circuit consisting of a current source (for example, a galvanic cell, battery or generator) and a resistor with resistance R. The current in a closed circuit is not interrupted anywhere, therefore, it also exists inside the current source. Any source represents some resistance to current. It's called current source internal resistance and is marked with the letter r.
In the generator r- this is the resistance of the winding, in a galvanic cell - the resistance of the electrolyte solution and electrodes.
Thus, the current source is characterized by the values of EMF and internal resistance, which determine its quality. For example, electrostatic machines have a very high EMF (up to tens of thousands of volts), but at the same time their internal resistance is huge (up to hundreds of Mohms). Therefore, they are unsuitable for receiving high currents. In galvanic cells, the EMF is only approximately 1 V, but the internal resistance is also small (approximately 1 ohm or less). This allows them to receive currents measured in amperes.
We came to the conclusion that in order to maintain a constant current in a closed circuit, it is necessary to include a current source in it. We emphasize that the task of the source is not to supply charges to the electric circuit (there are enough of these charges in the conductors), but to make them move, to do the work of moving charges against the forces of the electric field. The main characteristic of the source is the electromotive force 1 (EMF) - the work done by external forces to move a single positive charge
Therefore, most people need associations or a critical mass in the planetary field in order to receive energy signals and memories of consciousness and be able to perceive the signals correctly. The 3D control system does not take into account ascension symptoms, consciousness related experiences, or many of the drastic changes that people of this Earth are undergoing. Grounding is a form of grounding on Earth and refers to direct contact bodies with the elements of the earth. This can be helpful for many people who experience lack of grounding and carnal discomfort during planetary changes.
The unit of measure for EMF in the SI system of units is Volt. The EMF of a source is 1 volt if it does 1 Joule of work while moving a charge of 1 Coulomb
To designate current sources on electrical circuits, a special designation is used (Fig. 397). 
rice. 397
The electrostatic field makes positive work by moving a positive charge in the direction of decreasing field potential. The current source conducts the separation of electric charges - positive charges accumulate on one pole, negative charges on the other. The strength of the electric field in the source is directed from the positive pole to the negative, so the work of the electric field to move the positive charge will be positive when it moves from "plus" to "minus". The work of external forces, on the contrary, is positive if positive charges move from the negative pole to the positive, that is, from “minus” to “plus”.
This is the fundamental difference between the concepts of potential difference and EMF, which must always be remembered.
Thus, the electromotive force of the source can be considered an algebraic quantity, the sign of which ("plus" or "minus") depends on the direction of the current. In the scheme shown in fig. 398, 
rice. 398
outside the source (in the external circuit), the current flows 2 from the “plus” of the source to the “minus”, inside the source from the “minus” to the “plus”. In this case, both external source forces and electrostatic forces in the external circuit do positive work.
If in some section of the electrical circuit, in addition to electrostatic forces, third-party forces also act, then both electrostatic and third-party forces "work" on the movement of charges. The total work of electrostatic and external forces to move a single positive charge is called the electric voltage in the circuit section 
In the case when external forces are absent, the electric voltage coincides with the potential difference of the electric field.
Let us explain the definition of voltage and the sign of the EMF on simple example. Let there be a source of external forces and a resistor in the section of the circuit through which the electric current flows (Fig. 399). 
rice. 399
For definiteness, we will assume that φ o > φ 1, that is, the electric current is directed from the point 0
to the point 1
. When connecting the source, as shown in Fig. 399 a, External forces of the source do positive work, so relation (2) in this case can be written as 
When the source is turned on again (Fig. 399 b), the charges inside it move against external forces, so the work of the latter is negative. In fact, the forces of the external electric field overcome external forces. Therefore, in this case, the considered relation (2) has the form 
For the flow of electric current through a section of the circuit that has electrical resistance, it is necessary to do work to overcome the forces of resistance. For a unit positive charge, this work, according to Ohm's law, is equal to the product IR = U which, of course, coincides with the voltage in this area.
Charged particles (both electrons and ions) inside the source move in some , therefore, from the side of the medium, they are also affected by retarding forces, which also need to be overcome. Charged particles overcome resistance forces due to the action of external forces (if the current in the source is directed from "plus" to "minus") or due to electrostatic forces (if the current is directed from "minus" to "plus"). It is obvious that the work to overcome these forces does not depend on the direction of motion, since the resistance forces are always directed in the direction opposite to the velocity of the particles. Since the resistance forces are proportional average speed movement of particles, then the work to overcome them is proportional to the speed of movement, therefore, to the strength of the current. Thus, we can introduce another characteristic of the source - its internal resistance r, similar to ordinary electrical resistance. The work to overcome the resistance forces when moving a unit positive charge between the poles of the source is A/q = Ir. We emphasize once again that this work does not depend on the direction of the current in the source.
If you don't have access to nature and want to create an electrical circuit with the Earth's field, you can also use a primer that is associated with the human body. Electrical potential grounding circuit depends on the location, atmospheric conditions, time of day and night, as well as on the moisture that is located on the surface of the Earth. Intuitive empaths and star seedlings who want to re-energize with the planetary body need to pay attention to their natural feelings because they need to know if they should be grounded or not.
1 The name of this physical quantity is unfortunate - so the electromotive force is work, and not a force in the usual mechanical sense. But this term is so established that it is not “in our power” to change it. By the way, the current strength is not a mechanical force either! Not to mention such concepts as “fortitude”, “willpower”, “divine power”, etc.
2 Recall that the direction of movement of positive charges is taken as the direction of movement of electric current.
In some cases, due to inorganic or external currents in certain areas, this practice may not be practical. For most people who are seeded by the Earth, in the phase of spiritual integration grounding will be felt positively and will be very beneficial to the body because it will act as a neuromodulator. Neuromodulation is a process in which the activity of the nervous system is regulated by regulating physiological levels through the stimulation of neurotransmitters. In this way, grounding changes the negative charge density in the energy field of a person and his nervous system and directly affects physiological processes such as brain chemistry.
"Measurement of EMF and internal resistance of a current source"
Discipline Physics
Vinogradov A.B.
Objective: to form the ability to determine the EMF and internal resistance of a current source using an ammeter and a voltmeter.
The Earth sends electromagnetic signals to support human bodies in adapting to her ascension, and this signal allows the human nervous system to better adapt to the demands placed on the body and brain during times of intense consciousness shifts. When we want to restore the electrical balance of brain activity, it can be especially helpful to surround nature, focus on deep breathing, and connect with the Earth or the element of water.
The kidneys are organs that provide energy. Currently, the human population is experiencing an epidemic of kidney disease caused by the inability of organs to quickly adapt to new circumstances, poor recognition of life-changing events, heart disease, overload with toxic chemicals, and negative emotions. The purpose of the kidneys is to remove harmful metabolic products excreted bladder, and maintaining proper blood chemistry and blood pressure as they control everything chemical substances dissolved in the bloodstream.
Equipment: VU-4M rectifier, ammeter, voltmeter, connecting wires, tablet No. 1 elements: key, resistor R1.
theoretical The content of the work.
Internal resistance of the current source.
When current passes through closed circuit, electrically charged particles move not only inside the conductors connecting the poles of the current source, but also inside the current source itself. Therefore, in a closed electrical circuit, external and internal sections of the circuit are distinguished. Outer section of the chain constitutes the entire set of conductors that is connected to the poles of the current source. Inner section of the chain is the power source itself. A current source, like any other conductor, has resistance. Thus, in an electrical circuit consisting of a current source and conductors with electrical resistance R , electric current does work not only on the outer, but also on the inner section of the circuit. For example, when an incandescent lamp is connected to the galvanic battery of a pocket flashlight, not only the lamp coil and the lead wires are heated by an electric current, but also the battery itself. The electrical resistance of the current source is called internal resistance. In an electromagnetic generator, the internal resistance is the electrical resistance of the generator winding wire. In the internal section of the electrical circuit, an amount of heat is released equal to
When the kidneys are weakened and overworked, toxic wastes accumulate in the blood and tissues, as well as chemicals that cannot be properly filtered. Kidney failure is increasing in the United States by 5% per year, with kidney dialysis or transplant being used as the treatment. Ten percent of the population has some form of diabetes and neurological discomfort, and the number appears to be steadily rising - in adults and children. What happened to our kidneys?
Eastern medical philosophy knows that the kidneys nourish the other organs of the body. They act as the roots of life, which are responsible for the protection of the body and the distribution of energy in all organs, reproductive functions and the entire body. The kidneys are relationship organs, so they suffer from interpersonal and sexual problems that can result from a lack of support from others or feeling unloved, or even from a lack of physical sensitivity. Emotions circulate in a personal energy area, and when it is released, you may have a sense of flow through which you feel emotions.
where r- internal resistance of the current source.
The total amount of heat released during the flow of direct current in a closed circuit, the external and internal sections of which have resistances, respectively, equal to R and r, equals
Any closed circuit can be represented as two resistors connected in series with equivalent resistances. R and r. Therefore, the resistance of the complete circuit is equal to the sum of the external and internal resistances:
. Since at serial connection Since the current in all sections of the circuit is the same, then the same current flows through the external and internal sections of the circuit. Then, according to Ohm's law, for a section of the circuit, the voltage drop in its external and internal sections will be respectively equal:
It allows you to release emotional pain and fear and relieves you of chronic kidney problems, opening up more emotional and spiritual energy expansion. When it is reversed, when the heart is closed from pain and fear, which blocks emotions, it affects the function of fluid management through the kidneys and disrupts the distribution of vital energy needed for a grounded, healthy and balanced mind and body.
Moreover, when our heart is healed, a flame burns inside, which is also fed. life energy stored in the kidneys. A triangular connector connects the heart to each kidney, which works in the luminous body like an electrical circuit. At the base of this triangle on the left and right are the kidneys, and the top point is associated with the heart. When the heart is healed, the flames in the heart and kidneys simultaneously activate the heart configuration in the inner twin flame. The double flame corresponds to the restored energy balance between the energy of the male and the female, i.e. structure of light created in the heart complex.
and
(3)
Electromotive force.
The total work of the forces of the electrostatic field during the movement of charges along a closed DC circuit is equal to zero. Consequently, all the work of the electric current in a closed electrical circuit is performed due to the action of external forces that cause the separation of charges inside the source and maintain a constant voltage at the output of the current source. Work attitude
performed by external forces to move the charge q
along the chain, to the value of this charge is called source electromotive force(EMF) 
:
Therefore, when the two fires are ignited in the heart, the vital essence stored in the kidneys helps carry the chi flame throughout the physical body to connect with the spiritual flame of the monadic body. The monad is the greater flame of the spirit, and physical body- the lesser flame of life essence or life force. When these two fires are ignited and combined, the flame explodes from the heart, which sends out the fire to support the growth of the essence of life created by the kidneys. Basically, the kidneys help build the inner luminous body needed to build the monadic body.
, (4)
- portable charge.
EMF is expressed in the same units as voltage or potential difference, i.e. in volts:
.
Ohm's law for a complete circuit.
Any visual exercise designed to create life force energy in the lower dienes and cause energy to circulate at the foot of the feet, strengthen the ability of the kidneys to store vital essence, help correct the grounding mechanism and perform the functions of physical blood purification. There are some kidney potentiating agents and herbs that are common in oriental medicine and are useful for toning kidney function, especially if there is a problem with grounding or core centering.
Kidney failure causes the adrenal glands to produce. The adrenal glands are glands that produce a lot of hormones, and it is well known that under pressure they pump cortisol into the bloodstream, which causes the human nervous system to go into a fight-or-flight state. Adrenaline is usually produced by both the adrenal glands and certain neurons, which can also be activated by emotional responses. Every emotional response has a behavioral component, an autonomic nervous system component, a glandular secretion, or a hormonal factor.
If, as a result of the passage of direct current in a closed electrical circuit, only heating of the conductors occurs, then according to the law of conservation of energy full work electric current in a closed circuit, equal to the work of external forces of the current source, is equal to the amount of heat released in the external and internal sections of the circuit:
Hormonal factors associated with stress and emotional pain include the release of adrenaline and adrenal responses - in response to fear-based feelings controlled by the sympathetic nervous system. The main emotion that releases adrenaline into the blood is fear.
In addition, the adrenal glands play an important role in the fight or flight response by increasing blood flow to the muscles and heart, and then the students expand and blood sugar levels rise. Adrenaline is pumped into the bloodstream when a person is provoked into acts of terrorism or fear in order to produce as much negative emotional energy as possible, which may be the main reason why the adrenal glands are completely depleted in most people. When a person does not correct this condition and still pumps adrenaline or other stress hormones into the bloodstream, the nervous system freezes, a state of shock and numbness.
. (5)
From expressions (2), (4) and (5) we obtain:
. (6)
, then
, (7)
At some point, when you are in constant pain or fear, due to an excessive load of adrenaline, the body and nervous system enter a state of numbness that shuts off emotional responses by shutting down the heart. The adrenal glands are located at the top of each kidney, so they are directly susceptible to kidney exhaustion, which naturally leads to the release of the adrenal glands. If we do something really unhealthy for our spirit and our day to day work is not in line with who we are, it also drains the kidneys, adrenaline and vitality.
. (8)
The current strength in an electrical circuit is directly proportional to the electromotive force
current source and is inversely proportional to the sum of the electrical resistances of the external and internal sections of the circuit. Expression (8) is called Ohm's law for a complete circuit.
When we have to deal with difficult stressors at work, in relationships or in other situations, the body can be subjected to deep unconscious emotional stress. We feel helpless and frustrated that we just have to work to meet financial obligations or survive. Our body gives us the message due to excessive exhaustion that we can no longer live in this way, we must make changes and the first change must be to realize consciousness through the death of the ego.
Thus, from the point of view of physics, Ohm's Law expresses the law of conservation of energy for a closed DC circuit.
Work order.
Preparing for work.
In front of you on the tables is a minilaboratory on electrodynamics. Its appearance is presented in l. R. No. 9 in figure 2.
On the left are a milliammeter, a VU-4M rectifier, a voltmeter, an ammeter. Tablet No. 1 is fixed to the right (see Fig. 3 in sheet file No. 9). Colored connecting wires are placed in the rear section of the case: the red wire is used to connect the VU-4M to the “+” jack of the tablet; white wire - for connecting VU-4M to the “-” socket; yellow wires - for connecting measuring devices to the elements of the tablet; blue - for interconnecting the elements of the tablet. The section is closed with a folding platform. In the working position, the platform is located horizontally and is used as a working surface when assembling experimental setups in experiments.
Planetary control over human kidneys Chi. We must strive to restore the heart center and make the kidneys more lofty goal associated with the ascension of the body. There are overlays encoding human bodies for enslavement, set at the time of birth, in the transduction sequence record in the core manifestation body or in the Tree of Life. The main tree grid manifestation template has a set of instructions for controlling the functions of organs and glands at the level of each dimension, as the glands secrete substances and hormones that allow human consciousness to move faster between dimensions.
2. Progress of work.
In the course of work, you will master the method of measuring the main characteristics of a current source, using Ohm's law for a complete circuit, which relates the current strength I in the circuit, EMF of the current source , its internal resistance r and external circuit resistance R ratio:
In the lands of the United Kingdom, the keys to awaken the structures of Albion are hidden, and they are giant sleeping creatures. The tags are used to guide humans on Earth for future timelines to work in slave colonies or various galactic human trafficking sites that are controlled by these extraterrestrial corrupt conglomerates and dragon groups.
The Black Sun Orion groups have reserved the right to certain human bodies, genetic material and the human Tree of Life, and that is why they control it. This makes it easier for them to control and control information related to soul structure and multidimensional anatomy. These are the Draconians who steal from the spiritual parts of the body, as well as from the organs and glands.
. (9)
1 way.
With 
the layout of the experimental setup is shown in Figure 1.
Study it carefully. When the switch is open B, the source is closed to a voltmeter, the resistance of which is much greater than the internal resistance of the source (r R ). In this case, the current in the circuit is so small that the value of the voltage drop across the internal resistance of the source can be neglected
, and the EMF of the source with a negligible error is equal to the voltage at its terminals 
, which is measured by a voltmeter, i.e.
. (10)
Thus, the EMF of the source is determined by the readings of the voltmeter with the key open.
If switch B is closed, the voltmeter will show the voltage drop across the resistor R :
. (11)
Then, based on equalities (9), (10), and (11), we can state that
(12)
From formula (12) it can be seen that in order to determine the internal resistance of the current source, it is necessary, in addition to its EMF, to know the current strength in the circuit and the voltage across the resistor R when the key is closed.
The current in a circuit can be measured with an ammeter. Wirewound resistor 
made from nichrome wire and has a resistance of 5 ohms.
Assemble the circuit according to the diagram shown in Figure 3.
After the circuit is assembled, you need to raise your hand, call the teacher to check the correct assembly of the electrical circuit. And if the chain is assembled correctly, then proceed to the work.
With the key open B, take the voltmeter readings and enter the voltage value in table 1. Then close the key B and again take the voltmeter readings, but already 
and ammeter readings. Enter the value of voltage and current in table 1.
Formulate Ohm's law for a complete circuit.
If we didn’t know the resistance values of the wire resistors, would it be possible to use the second method and what needs to be done for this (maybe, for example, you need to include some device in the circuit)?
be able to collect electrical circuits used in work.
Literature
Kabardin O. F. Ref. Materials: Proc. A guide for students. - 3rd ed. - M.: Education, 1991. - p.: 150-151.
Student's handbook. Physics / Comp. T. Feshchenko, V. Vozhegova.–M.: Philological society "WORD", OOO "Firma" "Publishing house AST", Center for the Humanities at the faculty of journalism of Moscow State University. M. V. Lomonosov, 1998. - p.: 124,500-501.
Samoilenko P.I. Physics (for non-technical specialties): Textbook. for general education medium institutions. Prof. Education / P. I. Samoylenko, A. V. Sergeev.-2nd ed., Ster.-M.: Publishing Center "Academy", 2003-p.: 181-182.
A source is a device that converts mechanical, chemical, thermal and some other forms of energy into electrical energy. In other words, the source is an active network element designed to generate electricity. Various types sources available on the power grid are voltage sources and current sources. These two concepts in electronics are different from each other.
DC voltage source
The voltage source is a device with two poles, its voltage at any time is constant, and the current passing through it has no effect. Such a source would be ideal, having zero internal resistance. In practical terms, it cannot be obtained.
At the negative pole of the voltage source, an excess of electrons accumulates, at the positive pole - their deficit. The states of the poles are maintained by the processes inside the source.
Batteries
Batteries store chemical energy internally and are capable of converting it into electrical energy. Batteries cannot be recharged, which is their disadvantage.
Batteries
Batteries are rechargeable batteries. When charging, electrical energy is stored internally in the form of chemical energy. During unloading, the chemical process takes place in opposite direction and electrical energy is released.
Examples:
- Lead-acid battery cell. It is made from lead electrodes and an electrolytic liquid in the form of sulfuric acid diluted with distilled water. The voltage per cell is about 2 V. In car batteries, six cells are usually connected in a series circuit, the resulting voltage at the output terminals is 12 V;
- Nickel-cadmium batteries, cell voltage - 1.2 V.
Important! At low currents, batteries and accumulators can be seen as a good approximation to ideal voltage sources.
AC voltage source
Electricity is produced at power stations with the help of generators and, after voltage regulation, is transmitted to the consumer. The alternating voltage of the 220 V home network in the power supplies of various electronic devices is easily converted to a lower indicator when using transformers.
Current source
By analogy, as an ideal voltage source creates a constant voltage at the output, the task of a current source is to give a constant current value, automatically controlling the required voltage. Examples are current transformers (secondary winding), photocells, collector currents of transistors.
Calculation of the internal resistance of the voltage source
Real voltage sources have their own electrical resistance, which is called "internal resistance". The load connected to the outputs of the source is referred to as "external resistance" - R.
The battery pack generates EMF:
ε = E/Q, where:
- E - energy (J);
- Q - charge (C).
The total emf of a battery cell is its open circuit voltage when there is no load. It can be controlled with good accuracy with a digital multimeter. The potential difference measured at the output contacts of the battery, when it is connected to a load resistor, will be less than its voltage when the circuit is open, due to the current flowing through the load external and through the internal resistance of the source, this leads to energy dissipation in it as thermal radiation .
The internal resistance of a chemical battery is between a fraction of an ohm and a few ohms, and is mainly related to the resistance of the electrolytic materials used in the battery.
If a resistor with resistance R is connected to a battery, the current in the circuit is I = ε/(R + r).
Internal resistance is not a constant value. It is affected by the type of battery (alkaline, lead-acid, etc.) and varies depending on the load value, temperature and age of the battery. For example, in disposable batteries, the internal resistance increases during use, and the voltage therefore drops until it reaches a state unsuitable for further use.
If the source EMF is a predetermined value, the internal resistance of the source is determined by measuring the current flowing through the load resistor.
- Since the internal and external resistance in the approximate circuit are connected in series, Ohm's and Kirchhoff's laws can be used to apply the formula:
- From this expression r = ε/I - R.
Example. A battery with a known EMF ε = 1.5 V is connected in series with a light bulb. The voltage drop across the light bulb is 1.2 V. Therefore, the internal resistance of the element creates a voltage drop: 1.5 - 1.2 \u003d 0.3 V. The resistance of the wires in the circuit is considered negligible, the resistance of the lamp is not known. The measured current passing through the circuit: I \u003d 0.3 A. It is necessary to determine the internal resistance of the battery.
- According to Ohm's law, the resistance of a light bulb is R \u003d U / I \u003d 1.2 / 0.3 \u003d 4 Ohms;
- Now, according to the formula for calculating the internal resistance, r \u003d ε / I - R \u003d 1.5 / 0.3 - 4 \u003d 1 Ohm.
In the event of a short circuit, the external resistance drops to almost zero. The current can only be limited by a small source resistance. The current generated in such a situation is so high that the voltage source may be damaged by the thermal effect of the current, and there is a risk of fire. The risk of fire is prevented by installing fuses, for example in car battery circuits.
Voltage source internal resistance - important factor when deciding how to transfer the most efficient power to the connected electrical appliance.
Important! Maximum power transfer occurs when the internal resistance of the source is equal to the resistance of the load.
However, under this condition, remembering the formula P \u003d I² x R, an identical amount of energy is given to the load and dissipated in the source itself, and its efficiency is only 50%.
Load requirements must be carefully considered before deciding on best use source. For example, a lead-acid car battery must provide high currents at a relatively low voltage of 12 V. Its low internal resistance allows it to do this.
In some cases, high voltage power supplies must have extremely high internal resistance in order to limit the short circuit current.
Features of the internal resistance of the current source
An ideal current source has infinite resistance, but for genuine sources one can imagine an approximate version. The equivalent circuit is a resistance connected in parallel to the source and an external resistance.
The current output from the current source is distributed as follows: part of the current flows through the highest internal resistance and through the low load resistance.
The output current will be from the sum of the currents on the internal resistance and the load Io \u003d Ir + Ivn.
It turns out:
In \u003d Io - Ivn \u003d Io - Un / r.
This dependence shows that when the internal resistance of the current source increases, the more the current on it decreases, and the load resistor receives most current. Interestingly, the voltage will not affect the current value.
Real source output voltage:
Uout \u003d I x (R x r) / (R + r) \u003d I x R / (1 + R / r). Rate this article:
8.5. Thermal action current
8.5.1. Current source power
The total power of the current source:
P full = P useful + P losses,
where P is useful - useful power, P is useful \u003d I 2 R; P loss - power loss, P loss = I 2 r ; I - current strength in the circuit; R - load resistance (external circuit); r is the internal resistance of the current source.
Apparent power can be calculated using one of three formulas:
P full \u003d I 2 (R + r), P full \u003d ℰ 2 R + r, P full \u003d I ℰ,
where ℰ is the electromotive force (EMF) of the current source.
Net power is the power that is released in the external circuit, i.e. on the load (resistor), and can be used for some purpose.
Net power can be calculated using one of three formulas:
P useful \u003d I 2 R, P useful \u003d U 2 R, P useful \u003d IU,
where I is the current in the circuit; U - voltage at the terminals (terminals) of the current source; R - load resistance (external circuit).
Loss power is the power that is released in the current source, i.e. in the internal circuit, and is spent on the processes taking place in the source itself; for some other purpose, the power loss cannot be used.
The power loss is usually calculated by the formula
P loss = I 2 r ,
where I is the current in the circuit; r is the internal resistance of the current source.
In the event of a short circuit, the useful power goes to zero
P useful = 0,
since there is no load resistance in the event of a short circuit: R = 0.
The apparent power in the event of a short circuit of the source coincides with the power losses and is calculated by the formula
P full \u003d ℰ 2 r,
where ℰ is the electromotive force (EMF) of the current source; r is the internal resistance of the current source.
Net power has maximum value in the case when the load resistance R is equal to the internal resistance r of the current source:
R = r.
Maximum useful power:
P useful max = 0.5 P full,
where P full - full power of the current source; P full \u003d ℰ 2 / 2 r.
Explicitly, the formula for calculating maximum useful power as follows:
P useful max = ℰ 2 4 r .
To simplify the calculations, it is useful to remember two points:
- if with two load resistances R 1 and R 2 the same useful power is allocated in the circuit, then internal resistance current source r is related to the indicated resistances by the formula
r = R 1 R 2 ;
- if the maximum useful power is released in the circuit, then the current I * in the circuit is two times less than the short circuit current i:
I * = i 2 .
Example 15. When shorted to a resistance of 5.0 ohms, a battery of cells produces a current of 2.0 A. The short circuit current of the battery is 12 A. Calculate the maximum useful power of the battery.
Decision . Let's analyze the condition of the problem.
1. When a battery is connected to a resistance R 1 = 5.0 Ohm, a current of I 1 = 2.0 A flows in the circuit, as shown in fig. a , defined by Ohm's law for a complete chain:
I 1 \u003d ℰ R 1 + r,
where ℰ is the EMF of the current source; r is the internal resistance of the current source.
2. When a battery is short-circuited, a short-circuit current flows in the circuit as shown in fig. b. The strength of the short circuit current is determined by the formula
where i is the short circuit current, i = 12 A.
3. When the battery is connected to the resistance R 2 \u003d r, a current of force I 2 flows in the circuit, as shown in fig. in , defined by Ohm's law for a complete circuit:
I 2 \u003d ℰ R 2 + r \u003d ℰ 2 r;
in this case, the maximum useful power is allocated in the circuit:
P useful max \u003d I 2 2 R 2 \u003d I 2 2 r.
Thus, to calculate the maximum useful power, it is necessary to determine the internal resistance of the current source r and the current strength I 2.
In order to find the current strength I 2, we write down the system of equations:
i \u003d ℰ r, I 2 \u003d ℰ 2 r)
and perform the division of equations:
i I 2 = 2 .
This implies:
I 2 \u003d i 2 \u003d 12 2 \u003d 6.0 A.
In order to find the internal resistance of the source r, we write down the system of equations:
I 1 \u003d ℰ R 1 + r, i \u003d ℰ r)
and perform the division of equations:
I 1 i = r R 1 + r .
This implies:
r \u003d I 1 R 1 i - I 1 \u003d 2.0 ⋅ 5.0 12 - 2.0 \u003d 1.0 Ohm.
Calculate the maximum useful power:
P useful max \u003d I 2 2 r \u003d 6.0 2 ⋅ 1.0 \u003d 36 W.
Thus, the maximum useful power of the battery is 36 watts.