Conservation of energy and Hefei: Difference between pages
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[[zh:合肥]] |
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[[Category:physics| ]] [[ja:エネルギー保存則]] [[nl:Eerste wet van de thermodynamica]][[sl:prvi zakon termodinamike]] |
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'''Hefei''' (合肥 [[pinyin]] he2 fei2) is the capital of [[Anhui]] Province of [[Peoples Republic of China|China]]. Formerly translated '''Hofei''' using the [[Wade-Giles]] system. Population: 0.772 million. Area: 120 km². The GDP per capita was ¥17770 (ca. US$2150) in 2003, ranked no. 91 among 659 Chinese cities. |
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== History == |
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'''Conservation of energy''' is the first law of [[thermodynamics]], and one of several [[conservation law]]s. |
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The city was known as Luzhou (庐州 [[pinyin]] lu2 zhou1) during [[Ming Dynasty|Ming]] and [[Qing Dynasty|Qing]] Dynasties. |
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It is stated as follows: |
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A famous [[Three Kingdoms]] battle was fought at what is currently Xiaoyao Jin (逍遥津 [[pinyin]] xiao1 yao2 jin1) in Hefei. General Zhang Liao of the '''Kingdom of Wei (魏 wei4)''' commanding 7,000 picked cavalry defeated the 100,000-men army of '''Kingdom of Wu (吳 wu2)'''. |
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:The total inflow of [[energy]] into a [[system]] must equal the total outflow of energy from the system, plus the change in the energy contained within the system. |
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== Geography == |
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Although ancient philosophers as far back as [[Thales of Miletus]] may have had inklings of the First Law, it was first stated in its modern form by the German surgeon [[Julius Robert von Mayer]] ([[1814]]-[[1878]]) in his "Remarks On the Forces of Inorganic Nature" in ''Annalen der Chemie und Pharmacie'', '''43''', 233 (1842). Mayer reached his conclusion on a voyage to the Dutch East Indies (now [[Indonesia]]), where he found that his patients' [[blood]] was a deeper red, because they were using consuming less [[oxygen]], and therefore less energy, to maintain their body temperature in the hotter climate. He had discovered that [[heat]] and [[mechanical work|work]] were both forms of energy, and later, after improving his knowledge of physics, he calculated a quantitative relationship between them. |
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Hefei locates 130 km west of [[Nanjing]]. |
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Meanwhile, in [[1843]] [[James Prescott Joule]] independently discovered the law by an experiment, now called the "Joule apparatus", in which a descending weight attached to a string caused a paddle immersed in water to rotate. He showed that the gravitational [[potential energy]] lost by the weight in descending was equal to the thermal energy ([[heat]]) gained by the water by [[friction]] with the paddle. |
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Hefei's annual average temperature about 15.7°C. Its annual precipitation is about 1000 mm. |
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Unfortunately for Mayer, his work was overlooked in favour of Joule's, and Mayer attempted to commit suicide. Later, Mayer's reputation was restored by a sympathetic account in [[John Tyndall]]'s ''Heat: A Mode of Motion'' (1863). |
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Chaohu Lake, a lake 15 km southeast of the city, is one of the largest freshwater lake in China. However, the lake has been polluted with nitrogen and phosphor in recent decades. |
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A similar law was written in the privately published ''Die Erhaltung der Kraft'' ([[1847]]) by [[Hermann von Helmholtz]]. |
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== Economy == |
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With the discovery of [[special relativity]] by [[Albert Einstein]], [[conservation of energy]] was shown to be a special case of a more general rule. According to special relativity, mass and energy are interchangable with the famous equation ''E = mc<sup>2</sup>''. |
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Before [[PRC]], Hefei was a town who industry was predominantly agriculture. Soon after the founding of PRC, the capital of Anhui was moved from [[Anqing]] to Hefei. To help development of the city, many talents were sent from other parts of the country to Hefei. Modern day Hefei has machinery, electronics, chemistry, steel, textile, and cigarette industries. |
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Conservation of energy can be shown through [[Noether's theorem]] to be the result of the time-invariance of the laws of physics. |
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== |
== Demographics == |
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One formulation for the first law of thermodynamics is |
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: <math> Q = \Delta E + W \qquad \qquad \qquad (1) </math> |
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where Q is heat transferred into the system from the surroundings, W |
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is work done ''by'' the system, and E is the internal energy of the system. |
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This energy is mostly kinetic energy: the potential energy can be assumed to |
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be negligible. Pressure-volume work (e.g. done by a gas on a piston) is |
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defined to be |
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: <math> W = P \Delta V \qquad \qquad \qquad (2) </math>. |
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Equation (1) can be interpreted as follows: Q is heat energy being |
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input into the system. The system the can use this incoming energy |
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to do two things: (1) do work, or (2) increase its own internal energy. |
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Here is an analogy: Q is income, which can then be spent to buy |
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things (W), or it can be saved in a bank account (<math> \Delta E </math>). |
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The majority of the population in Hefei is [[Han Chinese]]. There is a small minority of [[Hui Chinese]] living in the city. |
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If all the heat is used to do work (<math> Q = W </math> and |
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<math> \Delta E = 0 </math>) then the system |
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is undergoing an [[isothermal process]], which means that its |
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temperature remains constant. This is because the system's internal |
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energy is proportional to its temperature. |
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== Sites of Interest == |
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If all the heat is used to increase internal energy, |
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(<math> Q = \Delta E </math> and <math> W = 0 </math>) |
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then the system is undergoing an |
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[[isochoric process]], also called isometric process. This is |
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a process in which the system's volume is constant: |
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<math> \Delta V = 0 </math> so that, according to equation (2), |
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''W'' = 0. |
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Xiaoyao Ford was the site of the battle mentioned above. The site where the 7,000 Wei cavalrymen were picked is also a famous attraction. |
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It is also possible for the heat energy to be used up partially by |
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doing work and partially by increasing internal energy. Examples of |
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such processes are the [[isobaric process]] and the [[adiabatic process]]. |
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Bao Zheng (999 - 1062), a Prime Minister of the [[Song dynasty]], was born in Hefei. He is more famous for his time as Magistrate because a TV series was made for him during the late 1980s and early 1990s. The Temple of Lord Bao, located near the city center, first built in 1066 close to the tomb of Bao. |
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Equation (1) is the one preferred by engineers. Another [[sign convention|convention]] preferred by chemists is |
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: <math> \Delta E = Q + W \qquad \qquad \qquad (3) </math> |
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where ''W'' is work done ''on'' the system by the surroundings. In this |
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case pressure-volume work is defined to be |
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: <math> W = -P \Delta V \qquad \qquad \qquad (4) </math>. |
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Equation (3) can be interpreted to mean thus: that heat Q and |
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work W are energies being transferred into or out of the system. |
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The system then responds by increasing or lowering its internal energy |
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accordingly. Equation (3) is more symmetric in the sense that |
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internal energy E is a state function (it is conservative; independent |
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of the chosen path (process) between initial and final thermal states) whereas |
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neither Q nor W are state functions: they do depend on which particular (thermodynamic) process is chosen to connect the initial and final thermostatic states. |
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== Colleges and Universities == |
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The law of conservation of energy excludes the possibility of [[perpetual motion|perpetuum mobile]] of the first kind. |
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[National] |
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==References== |
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*[[University of Science and Technology of China]] (中国科学技术大学) |
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* ''Engines of Our Ingenuity'', episode 722 - radio broadcast by John Lienhard, produced by KUHF-FM Houston) |
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*[[Hefei University of Technology]] (合肥工业大学) |
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* Peter J. Nolan, ''Fundamentals of College Physics'', 2nd edition, William C. Brown Publishers, 1995. |
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** Chapter 17, ''Thermodynamics''. |
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[Public] |
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* Oxtoby & Nachtrieb, ''Principles of Modern Chemistry'', 3rd edition, Saunders College Publishing, 1996. |
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*Anhui Medical University (安徽医科大学) (founded 1926) |
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** Chapter 8, ''Thermodynamic Processes and Thermochemistry''. |
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*Anhui University (安徽大学) |
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*Anhui Agricultural University (安徽农业大学) |
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*Anhui College of Traditional Chinese Medicine (安徽中医学院) |
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*Anhui Institute of Architecture & Industry (安徽建筑工业学院) |
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Note: Institutions without full-time bachelor programs are not listed. |
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== External Links == |
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*[http://www.hefei.gov.cn/English/default.asp Hefei Government English Website] |
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Revision as of 09:32, 4 March 2004
Hefei (合肥 pinyin he2 fei2) is the capital of Anhui Province of China. Formerly translated Hofei using the Wade-Giles system. Population: 0.772 million. Area: 120 km². The GDP per capita was ¥17770 (ca. US$2150) in 2003, ranked no. 91 among 659 Chinese cities.
History
The city was known as Luzhou (庐州 pinyin lu2 zhou1) during Ming and Qing Dynasties.
A famous Three Kingdoms battle was fought at what is currently Xiaoyao Jin (逍遥津 pinyin xiao1 yao2 jin1) in Hefei. General Zhang Liao of the Kingdom of Wei (魏 wei4) commanding 7,000 picked cavalry defeated the 100,000-men army of Kingdom of Wu (吳 wu2).
Geography
Hefei locates 130 km west of Nanjing.
Hefei's annual average temperature about 15.7°C. Its annual precipitation is about 1000 mm.
Chaohu Lake, a lake 15 km southeast of the city, is one of the largest freshwater lake in China. However, the lake has been polluted with nitrogen and phosphor in recent decades.
Economy
Before PRC, Hefei was a town who industry was predominantly agriculture. Soon after the founding of PRC, the capital of Anhui was moved from Anqing to Hefei. To help development of the city, many talents were sent from other parts of the country to Hefei. Modern day Hefei has machinery, electronics, chemistry, steel, textile, and cigarette industries.
Demographics
The majority of the population in Hefei is Han Chinese. There is a small minority of Hui Chinese living in the city.
Sites of Interest
Xiaoyao Ford was the site of the battle mentioned above. The site where the 7,000 Wei cavalrymen were picked is also a famous attraction.
Bao Zheng (999 - 1062), a Prime Minister of the Song dynasty, was born in Hefei. He is more famous for his time as Magistrate because a TV series was made for him during the late 1980s and early 1990s. The Temple of Lord Bao, located near the city center, first built in 1066 close to the tomb of Bao.
Colleges and Universities
[National]
- University of Science and Technology of China (中国科学技术大学)
- Hefei University of Technology (合肥工业大学)
[Public]
- Anhui Medical University (安徽医科大学) (founded 1926)
- Anhui University (安徽大学)
- Anhui Agricultural University (安徽农业大学)
- Anhui College of Traditional Chinese Medicine (安徽中医学院)
- Anhui Institute of Architecture & Industry (安徽建筑工业学院)
Note: Institutions without full-time bachelor programs are not listed.