process
/kloc-in the middle of the 0/9th century, the discovery of the law of conservation of energy is a very important law in natural science. It is an inevitable event that human beings gradually accumulate the laws of natural science to a certain extent. However, the result is still tortuous, difficult and exciting. Understanding the discovery process of the law of conservation of energy is a theory used to understand the accumulation and formation of the development of natural science. This paper briefly introduces the discovery process of the law of conservation of energy.
Prepare for the discovery of the law of conservation of energy
Law of conservation of energy, laws of mechanical energy and thermal energy. Needless to say, it is found that there is a deeper study of machinery and heat energy. Now let's introduce these two aspects.
Vigor and debate
Descartes (Descartes,No. 1596- 1650) discussed the problem of collision in his book Philosophy, and introduced the concept of measuring the momentum of motion in 1644. In 1687, Newton (ISAC· Newton, 1642- 1727) criticized Descartes Leibniz (Gottfried Wilhelm Leibniz, 1646- 1765438+) in his works. The momentum measured by Newton is also called a person's strength. Leibniz claims that only 1669 Huygens' conclusion is consistent. "The collision problem of two objects collides with each other, and the square sum of their product mass and velocity remains unchanged before and after the collision." Descartes and Leibniz, two schools of thought formed since Leibniz, have caused controversy. This debate lasted for nearly half a century, and many scholars participated in it. Until 1743, the French scholar D'Alembert (17 17- 1783) said in his "Dynamic" that "this measure should be promoted and given to the recipients". "Here, D'Alembert reveals that viability is a measure of distance force and momentum is a measure of role. The argument was finally settled. As a formal mechanism of long-term vitality of mechanics, it is generally accepted.
The vitality mechanics is closed, and Tong Li doesn't understand it. Until 1807, British scholar Thomas Young (Thomas Young,1773,5, 10-1829,5,10) introduced energy, and183/kl. The concept of force action is introduced, and a factor 1/2 is added in front of vitality, which is called kinetic energy, and the integrated power given by the following formula is related to kinetic energy.
The equation F = 1/2MV2 represents the kinetic energy of the force acting on the object. This is the essence of conservation of mechanical energy. /& gt； The invention of thermometer involves the accurate theory of latent heat of thermal thermometer from manufacturer. Galileo galilei (1564- 1642) began to make thermometers in Italy from17th century. However, due to the inconvenience of temperature scale, it is rarely used by future generations.
The German physicist Warren Hay (,1686- 1736), an early practical temperature scale, began to use mercury thermometers from 17 14, and constantly improved them until 17 17. It was not until the death of Warren Sea that scientists officially determined the Fahrenheit scale: the boiling point of water is 2 12 degrees, 32 degrees, and the freezing point of water. Therefore, such requirements try to avoid negative values in the usual temperature.
Camera Ear Hughes was invented by Swedish astronomer Camera Ear Hughes (anders celsius, 170 1- 1744) between 1742 and 1743. The freezing temperature of water in the standard state is 100℃. The International Conference on Weights and Measures became an international standard in 1948.
The necessary conditions for accurate programming of the thermometer can be used to measure the temperature changes of various substances under different conditions. The earliest temperature and heat are the heat at this temperature.
In the 50-year18th century, British scientist Joseph Black (1728- 1799) mixed ice with water with the same weight as172 f, and found that the average temperature was102 f, but at 32°F,
Blake's conclusion: when ice melts, it needs to absorb a lot of heat. Heat will turn ice into water, but it will not cause the temperature to rise. He also guessed that the heat absorbed by the melting ice was certain. In order to find out this problem, he did experiments, and in turn, observed that water also released a certain amount of heat during solidification. The supercooling oscillation at 4℃ is indeed the temperature rise of partial cooling water freezing. After the supercooled water is completely solidified, the temperature rises to 0℃ and enters the ice water. The results show that the heat released from solidified water. Blake found that a large number of biological state changes (melting, solidification, vaporization and condensation) have this effect in the experiments of various substances. He used a glass container full of alcohol, and the alcohol in the glass container that sucked out the air volatilized quickly, which was the result of condensation of many small droplets outside the glass curtain wall. Liquid (alcohol) shows that it evaporates and absorbs a lot of hot glass cover, thus cooling the condensation of water droplets on the front outer wall.
The heat needed by Blake was measured in a very simple and intuitive way. He used a stable fire to boil one kilogram of water at 0℃, and then continued to burn the fire until the water completely evaporated. The measured time of boiling water burning from 0℃ is 4.5 times that of water boiling, indicating that the heat ratio is 100:450. Of course, this is a very rough experiment. What is the measured value? There is a big error, and now the ratio is 100:539. The black color measured by a similar method needs a certain amount of ice to melt, which is equal to the heat required to heat 77.8℃. When the same weight of water is heated to140 F, this value is a little small,143 F (equivalent to 80°C), but at that time, this measurement result was a hard-won correct value.
Based on these experimental facts, Blake began to realize that heat and temperature are two different concepts in 1760, and then he introduced the concept of "latent heat" in 176 1.
Subsequently, French scientists lavoisier (1743- 1794) and Laplace (1749- 1827) cooperated with each other. 1822, French scholar Jean-batiste Joseph Fourier (1768 to 1830) published his summary of thermal analysis theory for many years.
Thermodynamic invention
Since ancient times, human beings have realized that heat is produced by mechanical movement. In the east and the west, there are ancient records of fire drilling to get fire, which is the early practice of mechanical movement transforming into heat energy. But no one thought that it has been quantitatively converted into mechanical energy and thermal energy for thousands of years. Until the American langford (No.of rumford Benjamin Thompson, 1753- 18 14) pointed out in Munich in 1798 that when boring drilling made a bronze barrel and a metal blank as hot as fire, it must continue to be cooled with water. Langford noticed that as a drill, as long as it doesn't stop heating the metal, if the heat is transferred to the original metal, the foot can melt it. Langford's conclusion is that boring mechanical motion is converted into heat energy, so heat is a form of motion, not a substance as previously thought. Langford also tried to calculate the mechanical energy produced by a certain amount of heat. The first Langford is what we now call the mechanical equivalent of heat. But his value is too high. Today, half a century later, Joule provides the correct value.
When it comes to the conversion of thermal energy into mechanical energy, the earliest thing to mention is the invention of the steam engine of Alexander hero (Alexander hero, about 62 years ago). The invention is a pipeline connected to the above two parts. When the water in the ball boils, steam is ejected through the pipe and the ball rotates rapidly. This is the first steam engine. But there was no actual ceremony or broadcast afterwards.
17 12 years, Thomas Newcomen (Thomas Newcomen, 1663- 1729) invented the atmospheric steam engine. This machine has a cylinder and a piston. When it works, it is the first to enter the cylinder. When the cylinder stops, the steam and water vapor in the cylinder will quickly reduce the pressure in the cylinder, thus sucking water up. Then the steam enters the cylinder, in the next cycle. The first steam engine, about 10 times per minute, can work automatically. Mine pumping greatly facilitates the work. Not only Britain, Germany and France can use it.
W (james watt, 1736- 18 19),1half of the steam engines in the 8th century were improved. One of the most important improvements is that the steam engine efficiency of the condenser of the invention is greatly improved, and the allowable steam engine speed of the centrifugal governor of the invention can be freely controlled. The improvement of Watt steam engine has been widely used in practical industry.
A perpetual motion machine is impossible.
The concept of perpetual motion machine originated in India and was brought to Europe in the12nd century.
According to records, it is called the first and most famous perpetual motion machine in Europe, and it was designed in Hennepin, in13rd century. As shown in the figure, the central axis of wheel rotation and the edge of wheel 12 are equipped with movable short rods, and the short end of each rod is equipped with iron balls.
Subsequently, the research and invention of perpetual motion machine emerged one after another. Although many scholars point out that perpetual motion machine is impossible, the research on perpetual motion machine is one after another.
During the Renaissance, the great Italian scholar Leonardo da Vinci (1452- 15 19) was a perpetual motion machine for many energy research. What is commendable is that he finally came to the conclusion that perpetual motion machine is impossible.
Da Vinci's contemporary was named Cardin Italy (Jerome Cardin, 150 1- 1576). As a famous perpetual motion machine, he first pointed out that the roots of cubic equations were impossible to solve.
Perpetual motion is impossible, and the Dutch physicist Simon Steven (1548 1620) should also be mentioned. Before16th century, it only dealt with the coordination and balance of forces of parallel systems, and the forces of a forcibly decomposed parallel system would converge into the force and balance of the system and would not be dealt with. In order to solve this problem, he solved the balance of three intersections and forces. The problem was solved by a clever statement. If you have a uniform chain ABC placed on an asymmetric wedge-shaped column (no friction), as shown in the figure. In this case, in the chain, the reaction force of the two contact surfaces and their own gravity. Just three intersecting forces. The chain won't slide to one side or the other? If so, one side? Stephen imagined that the sky was closed at the bottom of the CDA chain, and the wedge carpet as shown in the figure finally solved this problem. Hanging at the bottom of the chain is balanced and hanging at the upper part of the chain. Hooves said, "If you think the chain is unbalanced and wedge-shaped, I can build a perpetual motion machine." In fact, if the chain slips, then you have to push out a closed chain, which will always slide down. This is obviously absurd, and the answer must be that the chain does not move. Therefore, he listed the equilibrium conditions of three forces. He felt that this proved to be very subtle. On the title page of Figure 2, his book Mathematical Memo was highly praised by his colleagues, and his tombstone was engraved with Italy. The solution of the power balance problem of the integrated system also marks maturity.
The understanding of perpetual motion cannot be restricted by perpetual motion in some countries. As early as 1775, the French Academy of Sciences decided not to publish perpetual motion newsletter. 19 17, the us patent office decided not to accept the patent application of perpetual motion machine.
According to F. Charlesworth of the British Patent Office, "The earliest patents for perpetual motion machines in Britain were between 1635, 16 17 and 1903. The British Patent Office received about 600 patent applications for perpetual motion machines, not including the patent applications for perpetual motion machines using the principle of gravity in the United States.
Discovery and encounter of fortress
On the basis of previous scientific research and the measurement and protection of mechanical energy, a lot of practice shows that it is impossible for other perpetual motion machines to announce the discovery of the law of conservation of energy through the mutual transformation of thermal energy, mechanical energy and thermal energy. Gradually mature. So the earliest beginning of Meyer's discovery.
Julius robert maillet (18 14- 1878) is a German physicist. University medical school, but he doesn't like being a doctor. He used to be a doctor on the ship and worked relatively freely.
In the west, a large number of bloodletting treatments have been carried out since the 4th century. One time was about releasing 12- 13 ounces (about 340-370 grams, one cup as much as possible) of blood, and some were bleeding all the time on the day when the patient felt dizzy. This therapy is based on the pathology of the so-called "fluid" theory in the ancient west, which holds that if there is too much or not enough fluid in the human body, such as blood, phlegm and bile, these fluids will cause disease. The function of bloodletting is to measure the elimination of excess fluid. The rich in the Middle Ages in the West, especially those noble elites and gentlemen, also bled regularly once a year, usually in spring. Another function of bloodletting is to make women look better. Western aesthetics are all white, but they don't blush. Western grandmothers often bleed. Meyer, as a doctor, needless to say, often uses bloodletting therapy to treat people.
About 1840 sailing to Java, he thought about the problem of animal body temperature and was interested in the physics of Surabaya. When he bled some sick sailors, he found that the venous blood was bright. First of all, he mistakenly thought that the artery was wrong. So, he thinks, blood is redder, unlike in temperate zone, the body in tropical zone needs more oxygen to burn to keep body temperature. This phenomenon shows that Meyer wants the fact that the body converts food into heat and the function of the body, and thus draws the conclusion that heat and work can be transformed into each other.
He also pointed out that many people failed in the experiment of perpetual motion machine, which left a profound impact on their childhood. He guessed that these mechanical jobs could not be produced. "
It was first mentioned in September 12, 184 1 and I wrote to a friend of thermal mechanical equivalent. He said: "I can explain the theory with mathematical reliability, but it is still very important to solve the following problems: how high must a heavy object (for example, 100 pounds) be lifted on the ground to carry out such a high degree of physical activity, and the amount of heavy exercise is exactly equal to one pound, which will turn ice into water at 0℃ for heating.
1842, Ford wrote an article and sent his views on the power in the inorganic world to Justus von Liebig (Justus von Liebig, 1803- 1873). German chemist Justus von Liebig immediately agreed to use this article. In this article, the mechanical equivalent, the first sign of heat, said: "The study found that the weight dropped from about 365 meters or more. His article was published.
Meyer was one of the first scholars in the thermal experiment of 1842 in May. 1842 in may, he used horse-drawn mechanical equipment to stir the kettle pulp, and compared the work done by horse pulp to raise the mechanical equivalent temperature of heat. His experiment is rougher than Joule's later experiments, but he deeply realized this problem, which is of great significance and the first sentence of the law of conservation of energy. 1842 wrote a letter to a friend at the end. He said, "I am aware of the absolute truth of the law, which is evidence to the contrary: it is a recognized scientific truth: the design of perpetual motion machine is absolutely impossible in theory (that is, even if people do not consider mechanical difficulties, such as friction, they cannot successfully design ideas). And all my statements can be drawn from the conclusion that this principle is not pure. If someone rejects my theorem, then I can immediately establish a perpetual motion machine. " paper
Meyer did not attract social attention. In order to make up for the deficiency of the first paper, he wrote a second paper, which was ignored and not adopted. He believes that the sun is the ultimate source of all life and non-life insurance on the earth.
Subsequently, Helmholtz and Joule's papers were published one after another, which will be the inventors of Helmholtz and Joule's energy conservation theorem. His early systematic papers not only denied it, but also attracted many attack articles. Besides, in 1848, he dealt a double blow to two children because his brother took part in revolutionary activities. 1849, Meyer came to a mental hospital from the third floor, where she became severely disabled and was later diagnosed with schizophrenia, where doctors thought he often talked about new discoveries, which was a mental symptom of an megalomaniac.
1858 Helmholtz read Meyer's paper 1852, and admitted this as early as in his paper "Fortress on Guangzhou". Clausius also thinks that Meyer is the discoverer of conservation law. Clausius, to be honest, Tindal (1820- 1893), an English vocalist, was recognized by the society until 1862 because John Tindal's work in the Royal Society of London. 1860, Meyer's early papers were translated into English and published. 1870, Meyer was elected as the correspondent of the Paris Academy of Sciences, and Poncelet was awarded the Pang Si Prize. The fate of hummel has greatly improved.
Helmholtz and Joule work
Helmholtz in his "Protection by Force,
Hermann von helmholtz (182 1- 1894) was born in a family of German tutors. Eight years after graduating from high school, he received public funds and entered the Royal Academy of Medical Sciences in Berlin. Helmholtz received his doctorate at 1842. 1845, he participated in the young scholars held in Berlin. After that, I often participated in the Institute of Activity Physics of the Association. Besides medical treatment, he also studies all the problems he is interested in.
A famous report was made in 1847, entitled "On Power Protection of Physics Research Institute". The report, his article Chronicle of Physics, unexpectedly suffered the same fate. Six years ago, the manuscript edited by Meyer, the editor thought, had no experimental facts, so he refused to publish it. He later published a pamphlet for another famous publisher. At the end of the article, the experiment of 1843 Joule is exactly the same, and it will soon be called "the highest and most important principle in nature". In just a few years, and because of the famous publisher, his fate and Meyer's are completely different. Later, Kelvin's concept of young energy, "potential energy" instead of "elasticity" and "kinetic energy" instead of "vitality", has been continuously changed in the past 200 years.
Helmholtz deserves attention to the role of organization. He brought into play the development of German scientists. 1870, his teacher Heinrich Gustav MAGNUS (1802- 1870), the first director of the German Institute of Physics, died. Or associate professor Helmholtz as the director's successor. Time lags far behind the scientific research level of Britain, France and Germany. As the Franco-Prussian War drew to an end, a large number of claims came from France and Germany, and Germany's economic situation improved. Helmholtz invested 3 million marks to set up a new institution. After five years of hard work, a new research institute was established. Later, the institute attracted a large number of outstanding young scholars, whose research topics were closely related to industrial development, and later formed a good tradition, German scientific research. German entrepreneur, institute inventor William Siemens (1823- 1883) and Helmholtz, the first supporter of the Berlin Physical Society, are old friends. Helmholtz needs ten years, just like the German Physical Society. German physics is known as the "Chancellor".
Joule is equivalent to mechanical thermal experiment.
J (James Scott Joule, 18 18- 1889) is the son of a wealthy British brewer. His financial situation allows him to do research all his life. Joule has suffered from spinal injury since he was a child. He can read his mind. His father provided him with a home laboratory. 1835, he met Dalton, a professor at Manchester University. After Joule's success, he mainly taught himself. Joule has little knowledge of mathematics, and his research mainly depends on measurement. 1840, he was accused of being a conductor. After many measurements, it is found that electric energy can be converted into heat energy, which reaches the law that the square of intensity under the action of heat generated by the current of conductor resistance is proportional to the sum of time. Write a document about this method in photovoltaic heat.
Later, Joule continued to explore the relationship between various forms of movement between energy conservation and emission reduction and transformation. 1843 published papers on electrolytic hydrothermal solution and thermal effect of electromagnetic and thermodynamic values. In particular, the last Joule British Conference announced: "Nature cannot be destroyed, and the consumption of mechanical energy always becomes quite hot, and heat is only a form of energy."
Since then, Joule has been continuously improved to improve the measurement accuracy. Finally, a physical constant called "mechanical equivalent of heat" is obtained, and then the Joule value is 423.9 kg m/kcal. The value of this constant is 4 18.4. The unit of joule heat in the international system of units, 1 calorie = 4. 184 joules. abstract
Only when the concepts of electricity and energy become clear, heat can be distinguished at the same time, and they can accurately measure temperature. Only when the actual person of the heat engine is familiar with the faults of a large number of perpetual motion machines can the conditions for discovering the law of conservation of energy be mature.
Even so, people's understanding of foresight is relatively slow. Meyer's experience illustrates this point.
Law of conservation of important energy
The law of conservation of energy is still the law of mechanics and the whole natural science. But it will still develop. 1905, Einstein (1879- 1955) published a famous paper, which expounded the enlightening viewpoint that "the law of conservation of mass and energy reveals the generation and transformation of light" in special relativity, and thought that in an isolated system, all particles of relativistic kinetic energy remained unchanged and remained during the interaction.