Presentation on why it is impossible to create a perpetual motion machine. Physics presentation on the topic “Perpetual motion machine” download for free. Perpetual motion machine in a watch

Plan 1) Introduction 2) Electric current 3) Direct current sources 4) Direct current electrical circuit 5) Ohm's law for a section of a circuit 6) Series and parallel connection of conductors. 7) Work and power of electric current. 8) Internal resistance of the current source. 9) Electromotive force. 10) Ohm's law for a complete circuit. 11) Literature

Introduction Ohm's Law (discovered in 1826) is a physical law that defines the relationship between voltage, current and conductor resistance in an electrical circuit. Named after its discoverer, Geogra Om. Ohm's law states: The current strength in a homogeneous section of a circuit is directly proportional to the voltage applied to the section and inversely proportional to the electrical resistance of this section. (Current strength is directly proportional to voltage and inversely proportional to resistance) And is written by the formula: Where: I current (A), U voltage (V), R resistance (Ohm).

Electric current Electric current is the orderly movement of electrical charges. Electric charges can move in an orderly manner under the influence of an electric field. An electric field can be created, for example, by two differently charged bodies. By connecting oppositely charged bodies with a conductor, it is possible to obtain an electric current flowing for a short interval of time.

Sources of direct current In order for an electric current to exist in a conductor for a long time, it is necessary to maintain constant the conditions under which the electric current arises. If at the initial moment of time the potential of point A of the conductor is higher than the potential of point B (Fig. 148), then the transfer of positive charge q from point A to point B leads to a decrease in the potential difference between them.

DC electric circuit In the external section of the circuit, electric charges move under the influence of electric field forces. The movement of charges inside a conductor does not lead to equalization of the potentials of all points of the conductor, since at each moment of time the current source delivers to one end of the electrical circuit exactly the same number of charged particles as it transferred to the other end of the external electrical circuit. Therefore, the voltage between the beginning and the end of the external section of the electrical circuit remains unchanged; The electric field strength inside the conductors in this circuit is non-zero and constant in time.

Serial and parallel connection of conductors. Conductors in DC electrical circuits can be connected in series or in parallel. When connecting conductors in series, the end of the first conductor is connected to the beginning of the second, etc. U = U 1 + U 2 + U 3 According to Ohm’s law for a section of the circuit, U 1 = IR 1, U 2 = IR 2, U 3 = IR 3 and U = IR When conductors are connected in series, their total electrical resistance is equal to the sum of the electrical resistances of all conductors.,

Ohm's law for a section of a circuit. The German physicist Georg Ohm () in 1826 discovered that the ratio of the voltage U between the ends of a metal conductor, which is part of an electrical circuit, to the current strength I in the circuit is a constant value: The unit of electrical resistance in SI ohm (Ohm). An electrical resistance of 1 ohm has a section of the circuit at which, at a current of 1 A, the voltage is 1 V:

Ohm's law for a section of a circuit. Experience shows that the electrical resistance of a conductor is directly proportional to its length l and inversely proportional to the cross-sectional area S: The experimentally established dependence of the current strength I on the voltage U and the electrical resistance R of a circuit section is called Ohm’s law for a circuit section:

Work and power of electric current. The work done by the forces of the electric field that creates an electric current is called the work of the current. The work A of the electric field forces or the work of the electric current on a section of the circuit with electrical resistance R during the time is equal to The power of the electric current is equal to the ratio of the work of the current A to the time during which this work is performed:

Work and power of electric current. If mechanical work is not performed on a section of the circuit under the influence of an electric field and chemical transformations of substances do not occur, then the work of the electric field only leads to heating of the conductor. (43.12) Law (43.12) was experimentally established by the English scientist James Joule () and the Russian scientist Emilius Christianovich Lenz (), therefore it is called Joule Lenz’s law.

Internal resistance of the current source. In an electrical circuit consisting of a current source and conductors with electrical resistance R, the electric current does work not only on the external, but also on the internal section of the circuit. The electrical resistance of a 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: 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 equal to R and r, respectively, is equal to

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.

Ohm's law for a complete circuit. 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, the total work of the electric current in the 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:

Literature 1) Physics textbook for grade 10. Authors: G. Ya. Myakishev 2) Internet site “Ohm’s Law” (om_content&view=article&id=215#q10)

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Biography of Georg Ohm History of the law Statement of the LAW Graph of current versus voltage Dependence of current versus resistance Ohm's law in integral form Ohm's law for a section of a circuit Ohm's law in differential form Ohm's law for alternating current Conclusion Contents

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Born in Erlanger, in the family of a poor mechanic. Georg's mother, Maria Elizabeth, died in childbirth when the boy was ten years old. His father, Johann Wolfgang, a very developed and educated man, instilled in his son a love of mathematics and physics from childhood, and placed him in a gymnasium that was supervised by the university; upon completion of the course in 1806. Ohm’s most famous works concerned questions about the passage of electric current and led to the famous “Ohm’s law”, which relates the resistance of a galvanic current circuit, the electromotive force in it and the current strength, and lies at the basis of all modern teaching about electricity.

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Georg Ohm, conducting experiments with a conductor, established that the current strength I in a conductor is proportional to the voltage U applied to its ends: or The proportionality coefficient was called electrical conductivity, and the value is usually called the electrical resistance of the conductor. Ohm's law was discovered in 1827. History of Ohm's Law

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Ohm's law is a physical law that defines the relationship between voltage, current and conductor resistance in an electrical circuit. Named after its discoverer, Georg Ohm. The essence of the law is simple: the current strength in a section of the circuit is directly proportional to the voltage at the ends of this section and inversely proportional to its resistance I~U, I~

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Graph of current versus voltage

The current strength is proportional to the voltage I~U Graph – linear dependence I, A U, V 2 4 8 5 10 20 0

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Dependence of current on resistance

The current strength is inversely proportional to the resistance Graph – branch of the hyperbola I, A R, Ohm 0 3 2 1 1 2 5

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Ohm's law in integral form A diagram to help you remember Ohm's law. You need to close the desired value, and two other symbols will give the formula for calculating it. Ohm's law for a section of an electrical circuit has the form: U = RI where: U - voltage I - current strength, R - resistance.

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Magic triangle: I U R I=U/R R=U/I U=IR Ohm's law for a section of a circuit

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If the circuit contains not only active, but also reactive components and the current is sinusoidal with a cyclic frequency ω, then Ohm's law is generalized; the quantities included in it become complex: where: U - voltage or potential difference, I - current strength, Z - complex resistance (impedance), R - total resistance, Rr - reactance (difference between inductive and capacitive), Ra - active (ohmic) resistance, independent of frequency, δ - phase shift between voltage and current. Ohm's law for alternating current

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A perpetual motion machine (lat. Perpetuum Mobile) is an imaginary device that allows you to obtain useful work greater than the amount of energy supplied to it (efficiency greater than 100%). Perpetual motion machine

What types of perpetual motion machines exist? Question: What types of perpetual motion machines exist? Answer: None. But, despite this, there is a classification of perpetual motion machines.

Perpetual motion machine (perpetuum mobile) - is divided into perpetual motion machines of the first kind and the second kind. The reasons why they cannot be constructed are called the first and second laws of thermodynamics. The realization that the creation of a perpetual motion machine was impossible prompted the Paris Academy of Sciences in 1775 to refuse to consider all such projects (the reason was approximately the following: “there is no such thing as a freebie”).

A perpetual motion machine of the first kind was supposed to work without extracting energy from the environment. A perpetual motion machine of the second kind is a machine that reduces the energy of a thermal reservoir and converts it entirely into work without any changes in the environment.

Perpetual motion model In Fig. Figure 1 shows one of the oldest designs of a perpetual motion machine. It represents a gear wheel, in the recesses of which weights that hinge on hinges are attached. The geometry of the teeth is such that the weights on the left side of the wheel are always closer to the axle than on the right. According to the author, this, in accordance with the law of the lever, should cause the wheel to constantly rotate. When rotating, the weights would swing out to the right and maintain the driving force. However, if such a wheel is made, it will remain motionless. The differential reason for this fact is that although the weights on the right have a longer lever, on the left there are more in number. As a result, the moments of forces on the right and left are equal. Rice. 1. One of the oldest designs of a perpetual motion machine

Arabian perpetual motion machine An Indian or Arabian perpetual motion machine with small obliquely fixed vessels partially filled with mercury.

Perpetual motion machine with permanent magnets

Perpetual motion machine and Archimedes' law In Fig. Figure 2 shows the design of another engine. The author decided to use Archimedes' law to generate energy. The law is that bodies whose density is less than the density of water tend to float to the surface. Therefore, the author placed hollow tanks on a chain and placed the right half under water. He believed that the water would push them to the surface, and the chain with wheels would thus rotate endlessly. The following is not taken into account: buoyant force is the difference between the water pressures acting on the lower and upper parts of an object immersed in water. In the design shown in the figure, this difference will tend to push out those tanks that are under water on the right side of the figure. But the lowest tank, which plugs the hole, will only be affected by the pressure force on its right surface. And it will exceed the total force acting on the remaining tanks. Therefore, the entire system will simply scroll clockwise until the water flows out. Rice. 2. Design of a perpetual motion machine based on Archimedes' law

Some examples of "perpetual motion machines"

Wheel with rolling balls Inventor's idea: A wheel with heavy balls rolling in it. Whatever the position of the wheel, the weights on the right side of the wheel will be further from the center than the weights on the left half. Therefore, the right half must always pull the left half and make the wheel turn. This means the wheel must rotate forever. Why the engine does not work: Although the weights on the right side are always further from the center than the weights on the left side, the number of these weights is less just enough so that the sum of the gravitational forces of the weights multiplied by the projection of the radii perpendicular to the direction of gravity on the right and left are equal (F i L i = F j L j).

Chain of balls on a triangular prism Inventor's idea: A chain of 14 identical balls is thrown through a triangular prism. There are four balls on the left, two on the right. The remaining eight balls balance each other. Consequently, the chain will go into perpetual motion counterclockwise. Why the motor does not work: The loads are driven only by the component of gravity parallel to the inclined surface. On a longer surface there are more loads, but the angle of inclination of the surface is proportionally less. Therefore, the gravitational force of the goods on the right, multiplied by the sine of the angle, is equal to the gravitational force of the goods on the left, multiplied by the sine of the other angle.

At the beginning of the 17th century, the remarkable Dutch physicist and engineer Simon Stevin (1548–1620), apparently the first in history, did the opposite. Experimenting with a triangular prism and a chain of 14 identical balls, he assumed that a perpetual motion machine is generally impossible (this is a law of nature), and from this principle he derived the law of equilibrium of forces on an inclined plane: the gravitational forces acting on the loads are proportional to the lengths of the planes on which they are lying. From this principle grew the vector law of addition of forces and the idea that forces need to be described by a new mathematical object - a vector. In addition, Simon Stevin did a lot of deep, pioneering work in physics and mathematics. He substantiated and introduced decimal fractions and negative roots of equations into circulation in Europe, formulated the conditions for the existence of a root in a given interval and proposed a method for its approximate calculation. Stevin was probably the first applied mathematician to translate his calculations into numbers. To solve specific practical problems, he constantly developed applied computing. Stevin also included accounting as a science of rational management, that is, he stood at the origins of mathematical methods in economics. Stevin believed that “the purpose of accounting is to determine the entire national wealth of the country.” He was superintendent of military and financial affairs for the great commander, creator of the modern regular army, Moritz of Orange. His position in modern terms is “Deputy Commander for Logistics.”

“Hottabych’s Bird” Inventor’s idea: A thin glass flask with a horizontal axis in the middle is soldered into a small container. The free end of the cone almost touches its bottom. A little ether is poured into the lower part of the toy, and the upper, empty part, is pasted over the outside with a thin layer of cotton wool. A glass of water is placed in front of the toy and tilted, forcing it to “drink.” The bird begins to bend over two or three times a minute and dip its head into the glass. Time after time, continuously, day and night, the bird bows until the water in the glass runs out.

Why this is not a perpetual motion machine: The bird's head and beak are covered with cotton wool. When the bird “drinks water”, the cotton wool becomes saturated with water. As water evaporates, the temperature of the bird's head decreases. Ether is poured into the lower part of the bird’s body, above which there are ether vapors (the air has been pumped out). As the bird's head cools, the vapor pressure at the top decreases. But the pressure at the bottom remains the same. The excess pressure of ether vapor in the lower part lifts the liquid ether up the tube, the bird's head becomes heavier and tilts towards the glass. As soon as the liquid ether reaches the end of the tube, the vapors of warm ether from the lower part will fall into the upper part, the vapor pressure will equalize and the liquid ether will flow down, and the bird will again raise its beak, while capturing water from the glass. The evaporation of water begins again, the head cools down and everything repeats. If the water did not evaporate, the bird would not move. Evaporation from the surrounding space requires energy (concentrated in water and ambient air). A “real” perpetual motion machine must work without the expenditure of external energy. Therefore, Hottabych's bird is not actually a perpetual motion machine.

Chain of floats Inventor's idea: A high tower is filled with water. A rope with 14 hollow cubic boxes with a side of 1 meter is thrown through pulleys installed at the top and bottom of the tower. The boxes located in the water, under the action of the Archimedes force directed upward, must sequentially float to the surface of the liquid, dragging the entire chain with them, and the boxes on the left descend down under the influence of gravity. Thus, the boxes alternately fall from air into liquid and vice versa. Why the engine does not work: Boxes entering the liquid encounter very strong resistance from the liquid, and the work to push them into the liquid is no less than the work done by the Archimedes force when the boxes float to the surface.

Archimedes screw and water wheel Inventor's idea: The Archimedes screw, rotating, lifts water into the upper tank, from where it flows out of the tray in a stream that hits the blades of the water wheel. The water wheel rotates the grindstone and at the same time moves, with the help of a series of gears, the same Archimedes screw that lifts water into the upper tank. The screw turns the wheel, and the wheel turns the screw! This project, invented back in 1575 by the Italian mechanic Strado the Elder, was then repeated in numerous variations. Why the engine doesn't work: Most perpetual motion machines designs could actually work if it weren't for the existence of friction. If this is an engine, there must also be moving parts, which means that it is not enough for the engine to rotate itself: it also needs to generate excess energy to overcome the friction force, which cannot be removed in any way.

Orfireus Machine Inventor's Idea: Some inventors of perpetual motion machines were simply swindlers who cleverly deceived the gullible public. One of the most prominent “inventors” was a certain Doctor Orfireus (real name - Bessler). The main element of its engine was a large wheel, which supposedly not only rotated by itself, but also lifted a heavy load to a considerable height. Why the engine does not work: The “perpetual motion machine” turned out to be far from eternal - it was powered by Orfireus’s brother and a maid, pulling on a skillfully hidden cord.

Magnet and gutters Inventor's idea: A strong magnet is placed on a stand. Two inclined gutters are leaning against it, one below the other, and the upper groove has a small hole in its upper part, and the lower one is curved at the end. If you place a small iron ball on the upper chute, then due to the attraction of the magnet it will roll upward, however, when it reaches the hole, it will fall into the lower chute, roll down it, rise along the final curve and again fall on the upper chute. Thus, the ball will run continuously, thereby achieving perpetual motion. The design of this magnetic perpetuum mobile was described in the 17th century by the English bishop John Wilkens. Why the motor does not work: The device would work if the magnet acted on the metal ball only while it was being lifted onto the stand along the upper chute. But the ball rolls down slowly under the influence of two forces: gravity and magnetic attraction. Therefore, by the end of the descent, it will not acquire the speed necessary to rise along the curve of the lower chute and begin a new cycle.

“Eternal water supply” The inventor’s idea: The water pressure in a large tank should constantly squeeze water through the pipe into the upper container. Why the engine does not work: The author of the project did not understand that the hydrostatic paradox lies in the fact that the water level in the pipe always remains the same as in the tank.

Automatic winding of watches Inventor's idea: The basis of the device is a large-sized mercury barometer: a bowl of mercury suspended in a frame, and a large flask of mercury tilted over it, neck down. The vessels are strengthened movably relative to each other; When the atmospheric pressure increases, the flask lowers and the bowl rises; when the pressure decreases, the opposite is true. Both movements cause a small gear to rotate, always in one direction, and the clock weights are lifted through the system of gears. Why this is not a perpetual motion machine: The energy required to operate the clock is “drawn” from the environment. In essence, this is not much different from a wind engine - except that it is extremely low in power.

Oil rising through the wicks Inventor's idea: Liquid poured into the lower vessel rises through the wicks into the upper vessel, which has a groove for draining the liquid. Along the drain, the liquid falls onto the wheel blades, causing it to rotate. Then the oil that has flowed down again rises through the wicks to the upper vessel. Thus, the stream of oil flowing down the chute onto the wheel is not interrupted for a second, and the wheel must always be in motion. Why the engine does not work: Liquid will not flow down from the upper, bent part of the wick. Capillary attraction, overcoming the force of gravity, lifted the liquid up the wick - but the same reason holds the liquid in the pores of the wet wick, preventing it from dripping from it.

Wheel with tilting weights Inventor's idea: The idea is based on the use of a wheel with unbalanced weights. Folding sticks with weights at the ends are attached to the edges of the wheel. In any position of the wheel, the loads on the right side will be thrown further from the center than on the left; this half, therefore, must pull the left and thereby cause the wheel to rotate. This means that the wheel will rotate forever, at least until the axle wears out. Why the engine does not work: The weights on the right side are always further from the center, but it is inevitable that the wheel will be positioned in such a way that the number of these weights is less than on the left. Then the system is balanced - therefore, the wheel will not rotate, but will stop after a few swings.

Installation of engineer Potapov Inventor's idea: Hydrodynamic thermal installation of Potapov with an efficiency exceeding 400%. An electric motor (EM) drives a pump (PS), which forces water to circulate along the circuit (shown by arrows). The circuit contains a cylindrical column (OK) and a heating battery (WH). The end of pipe 3 can be connected to the column (OK) in two ways: 1) to the center of the column; 2) tangent to the circle forming the wall of the cylindrical column. When connected according to method 1, the amount of heat given off to the water is equal (taking into account losses) to the amount of heat emitted by the battery (BT) into the surrounding space. But as soon as the pipe is connected using method 2, the amount of heat emitted by the battery (BT) increases 4 times! Measurements carried out by our and foreign specialists have shown that when 1 kW is supplied to the electric motor (EM), the battery (BM) produces as much heat as it should have if 4 kW was consumed. When the pipe is connected according to method 2, the water in the column (OK) receives a rotational movement, and it is this process that leads to an increase in the amount of heat emitted by the battery (BT).

Why the engine does not work: The described installation was actually assembled at NPO Energia and, according to the authors, it worked. The inventors did not question the correctness of the law of conservation of energy, but argued that the engine draws energy from the “physical vacuum.” Which is impossible, because the physical vacuum has the lowest possible energy level and it is impossible to draw energy from it. A more prosaic explanation seems most likely: the liquid is unevenly heated across the cross-section of the pipe and, as a result, errors occur in temperature measurements. It is also possible that energy, against the will of the inventors, is “pumped” into the installation from the electrical circuit.

Moon and planets Inventor's idea: Perpetual motion of the Moon around the Earth and planets around the Sun. Why the engine does not work: There is a confusion of concepts here: “perpetual motion” and “perpetual motion”. The total (potential and kinetic) energy of the Solar system is a constant quantity, and if we want to do work at its expense (which, in principle, is not excluded), then this energy will decrease. But we still won’t get “free” work.

And yet it exists? The French Academy of Sciences, which once refused to accept projects for perpetual motion machines, thereby slowed down technical progress, delaying for a long time the emergence of a whole class of amazing mechanisms and technologies. Only a few developments managed to break through this barrier.

PERPETUAL MOTION IN WATCHES One of them is a watch that does not require winding, which, ironically, today is produced in France. The source of energy is fluctuations in air temperature and atmospheric pressure during the day. A special hermetic container “breathes” slightly depending on changes in the environment. These movements are transmitted to the mainspring, winding it. The mechanism is thought out so finely that a change in temperature of just one degree ensures the clock runs for the next two days. If it is in good working order, this mechanism will function exactly as long as the Sun shines and the Earth exists, that is, almost forever.

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Educational:

Involving the student in an active cognitive process on the topic “Perpetual motion machine”. Formation of skills for studying physical concepts in this topic.

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Educational:

Fostering an attentive, friendly attitude towards the answers of your classmates, fostering personal responsibility for performing collective work.

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Developmental:

Developing the skills and abilities of students to work independently or in a group, broadening their horizons, increasing erudition, developing interest in physics.

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Equipment:

multimedia board multimedia projector personal computer

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It has long been known that the idea of ​​a perpetual motion machine is not feasible, but it is very interesting and educational from the point of view of the history of the development of science and technology. Indeed, in the search for a perpetual motion machine, scientists were able to better understand the basic physical principles. Moreover, the inventors of perpetual motion machines are shining examples for studying certain aspects of human psychology: ingenuity, perseverance, optimism and fanaticism. During the classes:

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Perpetual motion machine