Internal resistance. Topic: determination of emf and internal resistance of a current source

Let's say there is a simple electrical closed circuit that includes a current source, for example a generator, galvanic cell or battery, and a resistor with a resistance R. Since the current in the circuit is not interrupted anywhere, it flows inside the source.

In such a situation, we can say that any source has some internal resistance that prevents current flow. This internal resistance characterizes the current source and is designated by the letter r. For a battery, internal resistance is the resistance of the electrolyte solution and electrodes; for a generator, it is the resistance of the stator windings, etc.

Thus, the current source is characterized by both the magnitude of the EMF and the value of its own internal resistance r - both of these characteristics indicate the quality of the source.

Electrostatic high-voltage generators (like the Van de Graaff generator or the Wimshurst generator), for example, are distinguished by a huge EMF measured in millions of volts, while their internal resistance is measured in hundreds of megaohms, which is why they are unsuitable for producing large currents.


Galvanic elements (such as a battery), on the contrary, have an EMF of the order of 1 volt, although their internal resistance is of the order of fractions or, at most, tens of ohms, and therefore currents of units and tens of amperes can be obtained from galvanic elements.

This diagram shows a real source with an attached load. Its internal resistance, as well as the load resistance, are indicated here. According to, the current in this circuit will be equal to:

Since the section of the external circuit is homogeneous, the voltage across the load can be found from Ohm’s law:

Expressing the load resistance from the first equation and substituting its value into the second equation, we obtain the dependence of the load voltage on the current in a closed circuit:

In a closed loop, the EMF is equal to the sum of the voltage drops across the elements of the external circuit and the internal resistance of the source itself. The dependence of load voltage on load current is ideally linear.

The graph shows this, but experimental data on a real resistor (crosses near the graph) always differ from the ideal:


Experiments and logic show that at zero load current, the voltage on the external circuit is equal to the source emf, and at zero load voltage, the current in the circuit is equal to . This property of real circuits helps to experimentally find the emf and internal resistance of real sources.

Experimental determination of internal resistance

To experimentally determine these characteristics, plot the dependence of the voltage on the load on the current value, then extrapolate it to the intersection with the axes.

At the point of intersection of the graph with the voltage axis is the value of the source emf, and at the point of intersection with the current axis is the value of the short circuit current. As a result, the internal resistance is found by the formula:

The useful power developed by the source is released to the load. The dependence of this power on the load resistance is shown in the figure. This curve starts from the intersection of the coordinate axes at the zero point, then increases to maximum value power, after which it drops to zero when the load resistance is equal to infinity.


To find the maximum load resistance at which the maximum power will theoretically develop at a given source, the derivative of the power formula with respect to R is taken and set equal to zero. Maximum power will develop when the external circuit resistance is equal to the internal resistance of the source:

This provision about the maximum power at R = r allows us to experimentally find the internal resistance of the source by plotting the dependence of the power released on the load on the value of the load resistance. Having found the real, and not theoretical, load resistance that provides maximum power, the real internal resistance of the power supply is determined.

The efficiency of a current source shows the ratio of the maximum power released at the load to full power, which in at the moment develops

We came to the conclusion that in order to maintain 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 electrical circuit (there are enough of these charges in conductors), but to force them to move, to do work to move charges against forces electric field. The main characteristics of the source is electromotive force 1 (EMF) - work done by external forces to move a unit positive charge

The unit of EMF in the SI system of units is the Volt. The emf of a source is 1 volt if it does 1 Joule of work when moving a charge of 1 Coulomb

  To designate current sources on electrical circuits, a special symbol is used (Fig. 397).

rice. 397
  An electrostatic field does positive work to move a positive charge in the direction of decreasing field potential. The current source conducts the separation electric charges− positive charges accumulate on one pole, negative charges on the other. The electric field strength in the source is directed from the positive pole to the negative pole, so the work of the electric field to move a 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 diagram shown in Fig. 398,

rice. 398
outside the source (in the external circuit) current flows 2 from the “plus” of the source to the “minus”, inside the source from “minus” to “plus”. In this case, both external source forces and electrostatic forces in the external circuit perform positive work.
  If in a certain section of the electrical circuit, in addition to electrostatic forces, there are also third-party forces, then both electrostatic and third-party forces “work” on the movement of charges. The total work of electrostatic and third-party forces to move a single positive charge is called electrical voltage in a section of the circuit

  In the case when there are no external forces, 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 using a simple example. Let there be a source of external forces and a resistor in the section of the circuit through which 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, The external forces of the source do positive work, so relation (2) in this case can be written in the form

  When the source is turned back on (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. Consequently, in this case, the relationship under consideration (2) has the form

  For flow electric current In a section of the circuit that has electrical resistance, work must be done to overcome the resistance forces. For a unit positive charge, this work, according to Ohm’s law, is equal to the product IR = U which naturally coincides with the voltage in this area.
  Charged particles (both electrons and ions) inside the source move in some environment, therefore, they are also subject to braking forces from the environment, 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 movement, since the resistance forces are always directed in the direction opposite to the speed of movement of the particles. Since the resistance forces are proportional to the average speed of movement of particles, 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 done to overcome resistance forces when moving a single positive charge between the poles of the source is equal to A/q = Ir. We emphasize once again that this work does not depend on the direction of the current in the source.

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, current strength is not mechanical force! Not to mention such concepts as “strength of spirit”, “willpower”, “divine power”, etc.
2 Let us recall that the direction of movement of the electric current is taken to be the direction of movement of positive charges.

An electric current in a conductor arises under the influence of an electric field, causing free charged particles to move in a direction. Creation of particle current - serious problem. Build a device that will maintain the field potential difference long time in one state - a task whose solution turned out to be within the power of humanity only towards the end of the 18th century.

First attempts

The first attempts to “store electricity” for its further research and use were made in Holland. The German Ewald Jürgen von Kleist and the Dutchman Pieter van Musschenbroek, 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 already took place under the influence of mechanical friction. It was possible to use a discharge through a conductor for a certain, fairly 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 (electric current created by the capacitor) lasted so short that it could not be created. In addition, the voltage supplied by the capacitor gradually decreases, which leaves no possibility of receiving long-term current.

It was necessary to look for another way.

First source

The Italian Galvani's experiments on "animal electricity" were an original attempt to find a natural source of current in nature. Hanging the legs of dissected frogs on the metal hooks of an iron grid, he drew attention to the characteristic reaction of the nerve endings.

However, Galvani's conclusions 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 turned out to be the complete opposite of previous hypotheses.

Volta noticed that a living organism is only an indicator of an electrical discharge. When current passes, the muscles of the paws contract, indicating a potential difference. The source of the electric field turned out to be the contact of dissimilar metals. The farther apart they are in a row chemical elements, the greater the effect.

Plates of dissimilar metals, lined with paper disks soaked in an electrolyte solution, created the necessary potential difference for a long time. And even though it was low (1.1 V), the electric current could be studied for a long time. The main thing is that the tension remained unchanged for just as long.

What's happening

Why does this effect occur in sources called “galvanic cells”?

Two metal electrodes placed in a dielectric play different roles. One supplies electrons, the other accepts them. The process of oxidation recovery reaction leads to the appearance of an excess of electrons on one electrode, which is called the negative pole, and a deficiency on the second, which we will designate as the positive pole of the source.

In the simplest galvanic cells, oxidation reactions occur on one electrode, reduction reactions on the other. Electrons come to the electrodes from the outer part of the circuit. The electrolyte is a conductor of ion current inside the source. The force of resistance controls 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 comes from 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 zinc sulfate solution. The solutions are separated by a porous spacer to avoid mixing, but they must come into contact.

If the circuit is closed, surface layer zinc is oxidized. In the process of interaction with the liquid, zinc atoms, turning into ions, appear in the solution. Electrons are released at the electrode, which can take part in the formation of current.

Once on the copper electrode, electrons take part in the reduction reaction. Copper ions come from the solution to the surface layer; during the reduction process, they turn into copper atoms, depositing on the copper plate.

Let's summarize what is happening: the process of operation of a galvanic cell is accompanied by the transition of electrons from the reducing agent to the oxidizing agent along the external part of the circuit. Reactions occur on both electrodes. An ion current flows inside the source.

Difficulty 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 batteries have a simpler structure. Two electrodes placed in one electrolyte fill the vessel - the battery body. Such design features simplify the structure and reduce the cost of batteries.

Any galvanic cell is capable of producing direct current.

The current resistance does not allow all the ions to appear on the electrodes at the same time, so the element operates for a long time. Chemical reactions the formation of ions sooner or later stops, the element is discharged.

The current source is of great importance.

A little about resistance

The use of electric current undoubtedly brought scientific and technological progress to a new level, gave him a gigantic push. 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 resistance. Physics, as a science of nature, tries to establish a balance and bring these circumstances into line.

Current resistance arises due to the interaction of electrically charged particles with the substance through which they move. Eliminate this process in normal temperature conditions impossible.

Resistance

The current source and the resistance of the external part of the circuit have 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 filling: 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 material. For example, the resistance of a metal wire increases with its length and decreases with increasing 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, an amount of heat is released in conductors proportional to the resistance. If the amount of heat is denoted by Q int. , current strength I, its flow time t, then we get:

  • Q internal = I 2 r t,

where r is the internal resistance of the current source.

In the entire chain, including both its internal and external parts, the total amount of heat will be released, the formula of which is:

  • Q total = I 2 r t + I 2 R t = I 2 (r +R) t,

It is known how resistance is denoted in physics: the external circuit (all elements except the source) has a resistance R.

Ohm's law for a complete circuit

Let us take into account that the main work is performed by external forces inside the current source. Its value is equal to the product of the charge transferred by the field and the electromotive force of the source:

  • q · E = I 2 · (r + R) · t.

realizing that the charge 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, the EMF of the current source is directly proportional and inversely proportional to the total (impact) resistance of the circuit.

Based on this pattern, it is possible to determine the internal resistance of the current source.

Source discharge capacity

The main characteristics of sources include discharge capacity. Maximum quantity The electricity generated during operation under certain conditions depends on the strength of the discharge current.

In the ideal case, 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 100 mA, it works for 5 hours.

Methods for charging batteries

Using batteries will drain them. charging of small-sized elements is carried out using a current whose strength does not exceed one tenth of the source capacity.

The following charging methods are available:

  • using constant current for a given time (about 16 hours with a current of 0.1 battery capacity);
  • charging with a decreasing current to a given potential difference;
  • use of asymmetrical currents;
  • sequential application of short pulses of charging and discharging, in which the time of the first exceeds the time of the second.

Practical work

A task is proposed: determine the internal resistance of the current source and the emf.

To perform it, you need to stock up on a current source, an ammeter, a voltmeter, a slider rheostat, a key, and a set of conductors.

Use will allow you to determine the internal resistance of the current source. To do this, you need to know its EMF and the value of the rheostat resistance.

The calculation formula for the current resistance in the external 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 external part of the circuit, measured with an ammeter; U is the voltage across the external resistance.

To increase accuracy, measurements are taken at least 5 times. What is this for? The voltage, resistance, current (or rather, current strength) measured during the experiment are used further.

To determine the EMF of the current source, we take advantage of the fact that the voltage at its terminals when the switch is open is almost equal to the EMF.

Let's assemble a circuit of a battery, a rheostat, an ammeter, and 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 internal resistance is significantly less than external resistance.

The practical function of batteries and batteries finds wide application. The indisputable environmental safety of 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-sized, lightweight, high-capacity rechargeable batteries are also extremely necessary in mobile devices. electronic devices. The amount of energy used in them is directly related to the performance of the devices.


We came to the conclusion that in order to maintain 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 electrical circuit (there are enough of these charges in conductors), but to force them to move, to do work to move charges against the forces of the electric field. The main characteristic of the source is electromotive force 1 (EMF) - the work done by external forces to move a single positive charge

Therefore, most people need associations or critical mass in the planetary field in order to receive energy signals and consciousness memories and be able to perceive the signals correctly. The 3D management system does not take into account ascension symptoms, experiences related to consciousness, or the many radical changes that are occurring in people of this Earth. Grounding is a form of grounding on the Earth and refers to direct contact of the body with the elements of the Earth. This can be helpful for many people who are experiencing a lack of grounding and carnal discomfort during planetary changes.

The unit of EMF in the SI system of units is the Volt. The emf of a source is 1 volt if it does 1 Joule of work when moving a charge of 1 Coulomb

To designate current sources on electrical circuits, a special symbol is used (Fig. 397).

rice. 397
  An electrostatic field does positive work to move a positive charge in the direction of decreasing field potential. The current source separates electrical charges - positive charges accumulate on one pole and negative charges on the other. The electric field strength in the source is directed from the positive pole to the negative, so the work of the electric field to move a 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 diagram shown in Fig. 398,

rice. 398
outside the source (in the external circuit) current flows 2 from the “plus” of the source to the “minus”, inside the source from “minus” to “plus”. In this case, both external source forces and electrostatic forces in the external circuit perform positive work.
  If in a certain section of the electrical circuit, in addition to electrostatic forces, there are also third-party forces, then both electrostatic and third-party forces “work” on the movement of charges. The total work of electrostatic and third-party forces to move a single positive charge is called electrical voltage in a section of the circuit

  In the case when there are no external forces, 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 using a simple example. Let there be a source of external forces and a resistor in the section of the circuit through which 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, The external forces of the source do positive work, so relation (2) in this case can be written in the form

  When the source is turned back on (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. Consequently, in this case, the relationship under consideration (2) has the form

  For electric current to flow through a section of a circuit that has electrical resistance, work must be done to overcome the resistance forces. For a unit positive charge, this work, according to Ohm’s law, is equal to the product IR = U which naturally coincides with the voltage in this area.
  Charged particles (both electrons and ions) inside the source move in a certain direction, therefore, they are also subject to braking forces from the environment, 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 movement, since the resistance forces are always directed in the direction opposite to the speed of movement of the particles. Since the resistance forces are proportional to the average speed of movement of particles, 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 done to overcome resistance forces when moving a single positive charge between the poles of the source is equal to 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 connected to the human body. The electrical potential of the ground circuit depends on the location, atmospheric conditions, time of day and night, and also on the moisture that is located on the surface of the Earth. Intuitive empaths and starseeds who want to re-establish energetic alignment with the planet's body need to pay attention to their natural feelings because they need to know whether they need to 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, current strength is not mechanical force! Not to mention such concepts as “strength of spirit”, “willpower”, “divine power”, etc.
2 Let us recall that the direction of movement of the electric current is taken to be the direction of movement of positive charges.

In some cases, due to inorganic or external currents in certain areas, this practice may not be practical. For most people who are Earth seeded, during the spiritual integration phase the 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 stimulation of neurotransmitters. Thus, grounding changes the density of negative charge in the energy field of a person and his nervous system and directly affects physiological processes, such as brain chemistry.

Laboratory work

“Measurement of EMF and internal resistance of a current source”

Discipline Physics

Teacher A.B. Vinogradov

Nizhny Novgorod

Purpose of the work: develop the ability to determine the EMF and internal resistance of a current source using an ammeter and voltmeter.

The Earth is sending 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 intense changes in consciousness. When we want to restore the electrical balance of brain activity, it can be especially helpful to surround ourselves with nature, focus on deep breathing and connect with the Earth or the water element.

Kidneys are organs that supply energy. The human population is currently experiencing an epidemic of kidney disease caused by the organs' inability to quickly adapt to new circumstances, poor recognition of life-changing events, heart disease, toxic chemical overload and negative emotions. The purpose of the kidneys is to remove harmful metabolic products secreted bladder, and maintaining proper blood chemistry and pressure as they control everything chemicals, dissolved in the bloodstream.

Equipment: rectifier VU-4M, ammeter, voltmeter, connecting wires, elements of tablet No. 1: key, resistor R1.

Theoretical 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. External chain section constitutes the entire set of conductors that are connected to the poles of the current source. Internal chain section- This is the current 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 external, but also on the internal section of the circuit. For example, when an incandescent lamp is connected to the galvanic battery of a flashlight, not only the lamp spiral and supply wires, but also the battery itself are heated by electric current. 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 and chemicals accumulate in the blood and tissues that cannot be filtered properly. Kidney failure is increasing in the United States by 5% per year, with kidney dialysis or transplantation being the treatment. Ten percent of the population has some form of diabetes and neurological discomfort, and this number appears to be steadily increasing - in adults and children. What happened to our kidneys?

Eastern medical philosophy knows that the kidneys nourish other organs of the body. They act as roots of life, which are responsible for protecting the body and distributing energy in all organs, reproductive functions and the whole body. The kidneys are relational organs, so they suffer from problems with interpersonal and sexual relations, which can result from a lack of support from others or feeling unloved or even a lack of physical sensitivity. Emotions circulate in the personal energy field, 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 outer and inner sections of which have resistances correspondingly equal R And r, equals

Any closed circuit can be represented as two series-connected resistors 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 in a series connection the current strength in all sections of the circuit is the same, then the same amount of current passes through the external and internal sections of the circuit. Then, according to Ohm’s law, for a section of the circuit, the voltage drops on its external and internal sections will be respectively equal:

It allows you to release emotional pain and fear and frees you from chronic problems with the kidneys, discovering greater emotional and spiritual expansion of energy. When it is the other way around, when the heart is closed from pain and fear, blocking emotions, it affects the fluid management function of the kidneys and disrupts the distribution of vital energy needed for a grounded, healthy and balanced mind and body.

Moreover, when our heart heals, a flame burns inside, which also feeds vital 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 to the left and right are the kidneys, and the top point is connected to the heart. When the heart is healed, the flame in the heart and kidneys simultaneously activates the heart configuration in the inner twin flame. The double flame corresponds to the restored energy balance between the energy of the male and female, i.e. the structure of the light created in the heart complex.


And

(3)

Electromotive force.

The total work done by the electrostatic field forces when charges move along a closed direct current circuit is zero. Consequently, all the work of an electric current in a closed electrical circuit is completed 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

, carried out by external forces to move the charge q along the chain, to the value of this charge is called electromotive force of the source(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- a lesser flame of vital essence or life force. When these two fires are ignited and united, a flame explodes from the heart, which sends out fire to support the growth of the life essence created by the kidneys. Basically, the kidneys help build the inner luminous body necessary for the embedding of the monadic body.


, (4)

- transferred 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 that aims to create vital energy energy in the lower dienes and causes energy to circulate at the base of the feet, strengthens the kidneys' ability to store vital essence, helps correct the grounding mechanism and perform physical blood purification functions. There are some kidney and herbal potentiating agents that are common to oriental medicine and are useful for toning kidney function, especially if there is a problem with grounding or core centering.

Kidney failure causes adrenal gland production. The adrenal glands are glands that produce many hormones, and it is well known that under pressure they pump cortisol into the bloodstream, causing the human nervous system goes into a fight or flight state. Adrenaline is usually produced both by the adrenal glands and by certain neurons that can also be activated by emotional reactions. Every emotional reaction has a behavioral component, a component of the autonomic nervous system, glandular secretion, or 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 time job 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 important role in the fight or flight response by increasing blood flow to the muscles and heart, and then the students dilate and blood sugar levels increase. Adrenaline is pumped into the bloodstream when a person is provoked to terrorist attacks or fear to produce as much negative emotional energy as possible, which may be the main reason why the adrenal glands are completely exhausted in most people. When a person does not correct this condition and is still pumping adrenaline or other stress hormones into the bloodstream, the nervous system freezes into a state of shock and numbness.


. (5)

From expressions (2), (4) and (5) we obtain:

. (6)

, That


, (7)

At some point when you experience constant pain or fear, due to excessive load adrenaline, the body and nervous system enter a state of numbness that shuts down emotional reactions, closing 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 adrenal failure. If we do something that's really unhealthy for our spirit and our daily work doesn't match who we are, it also depletes 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 subject to deep unconsciousness emotional stress. We feel helpless and frustrated that we must simply work to meet financial obligations or survive. Our body gives us a message due to excessive exhaustion that we can no longer live in the same 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 to do the job.

In front of you on the tables is a mini-laboratory 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, and an ammeter. Tablet No. 1 is fixed to the right (see Fig. 3 in sheet No. 9). The rear section of the case contains colored connecting wires: the red wire is used to connect the VU-4M to the “+” socket of the tablet; white wire - for connecting the VU-4M to the “-” socket; yellow wires - for connecting measuring instruments to the elements of the tablet; blue - for connecting the tablet elements together. 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.

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2. Work progress.

As you work, you will learn a method for measuring the basic 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:

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. (9)

1 way.

WITH A diagram of the experimental setup is shown in Figure 1.

Study it carefully. When switch B is open, 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 key B 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 is clear that to determine the internal resistance of a 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 switch is closed.

The current in a circuit can be measured using an ammeter. Wirewound resistor made of 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 and call the teacher so that he can check the correct assembly of the electrical circuit. And if the chain is assembled correctly, then start doing the work.

With key B open, take voltmeter readings and enter the voltage value in Table 1. Then close key B and again take voltmeter readings, but this time and ammeter readings. Enter the voltage and current values ​​in Table 1.

State Ohm's law for the complete circuit.

If we did not know the resistance values ​​of the wirewound resistors, would it be possible to use the second method and what needs to be done for this (maybe, for example, we need to connect some device to the circuit)?

Be able to assemble electrical circuits used in work.

Literature

    Kabardin O.F.. Reference. Materials: Textbook. A manual for students.-3rd ed.-M.: Education, 1991.-p.:150-151.

    School Student's Handbook. Physics / Comp. T. Feshchenko, V. Vozhegova. – M.: Philological Society “SLOVO”, LLC “Firm” “AST Publishing House”, Center humanities at the Faculty of Journalism of Moscow State University. M. V. Lomonosova, 1998. - p.: 124,500-501.

    Samoilenko P.I.. Physics (for non-technical specialties): Textbook. for general education institutions Prof. Education / P. I. Samoilenko, A. V. Sergeev. - 2nd ed., St.-M.: Publishing Center "Academy", 2003, pp.: 181-182.

Laboratory work No. 8

Topic: "Determination of electromotive force and internal resistance of a current source».

Target: learn to determine the electromotive force and internal resistance of the source electrical energy.

Equipment: 1. Laboratory ammeter;

2. Source of electrical energy;

3. Connecting wires,

4. Set of resistances 2 Ohm and 4 Ohm;

5. Single-pole switch; key.

Theory.

The appearance of a potential difference at the poles of any source is the result of the separation of positive and negative charges in it. This separation occurs due to the work done by outside forces.

Forces of non-electric origin acting on free charge carriers from current sources are called outside forces.

When electric charges move along a direct current circuit, external forces acting inside the current sources perform work.

Physical quantity, equal to the ratio of the work A st of external forces when moving a charge q inside a current source to the value of this charge, is calledsource electromotive force (EMF):

EMF is determined by the work done by external forces when moving a single positive charge.

Electromotive force, like potential difference, is measured in volts[IN].

To measure EMF source, it is necessary join to him voltmeter with open circuit.

The current source is a conductor and always has some resistance, so the current generates heat in it. This resistance is called internal source resistance and denote r.

If the circuit is open, then the work of external forces is converted into potential energy of the current source. In a closed circuit, this potential energy is spent on work moving charges in the external circuit with resistance R and in the internal part of the circuit with resistance r, i.e. ε = IR + Ir .

If the circuit consists of an external part with a resistance R and an internal part with a resistance r, then, according to the law of conservation of energy, the emf of the source will be equal to the sum of the voltages on the external and internal sections of the circuit, because when moving along a closed circuit, the charge returns to starting position, Where IR is the voltage on the external section of the circuit, and Ir- voltage on the internal section of the circuit.

Thus, for a section of the circuit containing EMF:

This formula expresses Ohm's law for a complete circuit : the current strength in a complete circuit is directly proportional to the electromotive force of the source and inversely proportional to the sum of the resistances of the external and internal sections of the circuit.

ε and r can be determined experimentally.

Often sources of electrical energy are connected together to power a circuit. The connection of sources to a battery can be serial or parallel.

In a series connection, two adjacent sources are connected by opposite poles.

That is, to connect batteries in series, the positive terminal of the first battery is connected to the “plus” of the electrical circuit. The positive terminal of the second battery is connected to its negative terminal, etc. The negative terminal of the last battery is connected to the “minus” of the electrical circuit.

The resulting battery in series connection has the same capacity as a single battery, and the voltage of such a battery is equal to the sum of the voltages of the batteries included in it. Those. If the batteries have the same voltage, then the battery voltage is equal to the voltage of one battery multiplied by the number of batteries in the battery.

1. The emf of the battery is equal to the sum of the emf of individual sourcesε= ε 1 + ε 2 + ε 3

2 . The total resistance of the source battery is equal to the sum of the internal resistances of the individual sources r batteries = r 1 + r 2 + r 3

If n identical sources are connected to a battery, then the emf of the battery is ε = nε 1, and the resistance r of the battery = nr 1

3.

In a parallel connection, all positive and all negative poles two orn sources.

That is, with a parallel connection, the batteries are connected so that the positive terminals of all batteries are connected to one point of the electrical circuit ("plus"), and the negative terminals of all batteries are connected to another point of the circuit ("minus").

Connect in parallel only sources With the same EMF. The resulting battery in parallel connection has the same voltage as a single battery, and the capacity of such a battery is equal to the sum of the capacities of the batteries included in it. Those. if the batteries have the same capacities, then the capacity of the battery is equal to the capacity of one battery multiplied by the number of batteries in the battery.



1. The emf of a battery of identical sources is equal to the emf of one source.ε= ε 1 = ε 2 = ε 3

2. Battery resistance is less than single source resistance r batteries = r 1 /n
3. Current strength in such a circuit according to Ohm's law

The electrical energy accumulated in a battery is equal to the sum of the energies of individual batteries (the product of the energies of individual batteries, if the batteries are the same), regardless of whether the batteries are connected in parallel or in series.

The internal resistance of batteries manufactured using the same technology is approximately inversely proportional to the battery capacity. Therefore, since with a parallel connection the capacity of the battery is equal to the sum of the capacities of the batteries included in it, i.e. it increases, the internal resistance decreases.

Work progress.

1. Draw a table:

2. Consider the ammeter scale and determine the value of one division.
3. Make an electrical circuit according to the diagram shown in Figure 1. Place the switch in the middle position.


Figure 1.

4. Close the circuit by introducing a lower resistance R 1 1 . Open the circuit.

5. Close the circuit by introducing more resistance R 2 . Write down the current value I 2 . Open the circuit.

6. Calculate the value of the emf and internal resistance of the source of electrical energy.

Ohm's law for the complete circuit for each case: And

From here we get formulas for calculating ε and r:

7. Write down the results of all measurements and calculations in a table.

8. Draw a conclusion.

9. Answer the security questions.

TEST QUESTIONS.

1. Expand the physical meaning of the concept “electromotive force of a current source”.

2. Determine the resistance of the external section of the circuit, using the results of the measurements obtained and Ohm's law for the complete circuit.

3. Explain why internal resistance increases when batteries are connected in series and decreases when batteries are connected in parallel compared to resistance r 0 one battery.

4. In what case does a voltmeter connected to the terminals of the generator indicate the EMF of the generator and in what case is the voltage at the ends of the external section of the circuit? Can this voltage also be considered the voltage at the ends of the internal section of the circuit?

Measurement option.

Experience 1. Resistance R 1 =2 Ohm, current I 1 =1.3 A.

Resistance R 2 =4 Ohm, current I 2 =0.7 A.