energy conservation law,能量守恒定律,即热力学第一定律
second law of thermodynamics,热力学第二定律，热力学基本定律之一，克劳修斯表述为：热量不能自发地从低温物体转移到高温物体。
Nernst's heat theorem/the third law of thermodynamics,其描述的是热力学系统的熵在温度趋近于绝对零度时趋于定值。而对于完整晶体，这个定值为零。
能量守恒定律可以表述为：一个系统的总能量的改变只能等于传入或者传出该系统的能量的多少。总能量为系统的机械能、热能及除热能以外的任何内能形式的总和。
如果一个系统处于孤立环境，即不可能有能量或质量传入或传出系统。对于此情形，能量守恒定律表述为：
“孤立系统的总能量保持不变。”
能量既不会凭空产生，也不会凭空消失，它只会从一种形式转化为另一种形式，或者从一个物体转移到其它物体，而能量的总量保持不变。能量守恒定律是自然界普遍的基本定律之一。
扩展资料：
第一定律的表述本质
常见表述：能量既不会凭空产生也不会凭空消失，它只会从一个物体转移到另一个物体，或者从一种形式转化为另一种形式，而在转化或转移的过程中，能量总量保持不变。
热力学第一定律：普遍的能量守恒和转化定律在一切涉及宏观热现象过程中的具体表现。热力学第一定律确认，任意过程中系统从周围介质吸收的热量、对介质所做的功和系统内能增量之间在数量上守恒。
热力学第一定律即能量守恒定律，它是人类经验的总结，不能用任何别的原理来证明。热力学系统能量表达为内能、热量和功，热力学第一定律是能量守恒的一种表达形式。从它导出的结论，还没有发现与事实有矛盾。
根据热力学第一定律可以设想，要制造一种机器，它既不靠外界供给能量，本身也不减少能量，却不断地对外做功而不消耗能量。人们把这种假想的机器称为第一类永动机。因为对外界做功就必须消耗能量，不消耗能量就无法对外界做功，因此第一定律也可以表达为“第一类永动机是不可能造成的”。
参考资料来源：百度百科-能量守恒定律
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第1个回答 推荐于2018-04-23
First law
Main article: First law of thermodynamics
“ In any process, the total energy of the universe remains constant. ”
More simply, the First Law states that energy cannot be created or destroyed; rather, the amount of energy lost in a steady state process cannot be greater than the amount of energy gained.
This is the statement of conservation of energy for a thermodynamic system. It refers to the two ways that a closed system transfers energy to and from its surroundings - by the process of heating (or cooling) and the process of mechanical work. The rate of gain or loss in the stored energy of a system is determined by the rates of these two processes. In open systems, the flow of matter is another energy transfer mechanism, and extra terms must be included in the expression of the first law.
The First Law clarifies the nature of energy. It is a stored quantity which is independent of any particular process path, i.e., it is independent of the system history. If a system undergoes a thermodynamic cycle, whether it becomes warmer, cooler, larger, or smaller, then it will have the same amount of energy each time it returns to a particular state. Mathematically speaking, energy is a state function and infinitesimal changes in the energy are exact differentials.
All laws of thermodynamics but the First are statistical and simply describe the tendencies of macroscopic systems. For microscopic systems with few particles, the variations in the parameters become larger than the parameters themselves, and the assumptions of thermodynamics become meaningless. The First Law, i.e. the law of conservation, has become the most secure of all basic laws of science. At present, it is unquestioned.
Second law
Main article: Second law of thermodynamics
“ There is no process that, operating in a cycle, produces no other effect than the subtraction of a positive amount of heat from a reservoir and the production of an equal amount of work. ”
This version is the so-called Kelvin-Planck Statement. In a simple manner, the Second Law states that energy systems have a tendency to increase their entropy (heat transformation content) rather than decrease it.
The entropy of a thermally isolated macroscopic system never decreases (see Maxwell's demon), however a microscopic system may exhibit fluctuations of entropy opposite to that dictated by the Second Law (see Fluctuation Theorem). In fact, the mathematical proof of the Fluctuation Theorem from time-reversible dynamics and the Axiom of Causality, constitutes a proof of the Second Law. In a logical sense the Second Law thus ceases to be a "Law" of Physics and instead becomes a theorem which is valid for large systems or long times.
Stephen Hawking described this using time as an entropy base. For example, when time moves in a forward direction and one, say, breaks a cup of coffee on the floor, no matter what happens, in our universe, one will never see the cup reform. Cups are breaking all the time, but never reforming. Since the Big Bang, the entropy of the universe has been on the rise, and so the Second Law states that this process will continue to increase.
Third law
Main article: Third law of thermodynamics
“ As temperature approaches absolute zero, the entropy of a system approaches a constant. ”
The Third Law says that constant is in fact zero. As the temperature approaches zero, the probability that the system, however complex, sits in its unique quantum ground state approaches one. The entropy of any unique state is zero, so the entropy approaches zero. More rigorously, if the system happens to have half-integer net spin, there are two degenerate ground states, related by time-reversal symmetry, so the dimensionless entropy approaches the natural log of two. However, that is the entropy for the whole system, and is negligible on the scale of any macroscopic system. Basically, no system can reach absolute zero.
Main article: First law of thermodynamics
“ In any process, the total energy of the universe remains constant. ”
More simply, the First Law states that energy cannot be created or destroyed; rather, the amount of energy lost in a steady state process cannot be greater than the amount of energy gained.
This is the statement of conservation of energy for a thermodynamic system. It refers to the two ways that a closed system transfers energy to and from its surroundings - by the process of heating (or cooling) and the process of mechanical work. The rate of gain or loss in the stored energy of a system is determined by the rates of these two processes. In open systems, the flow of matter is another energy transfer mechanism, and extra terms must be included in the expression of the first law.
The First Law clarifies the nature of energy. It is a stored quantity which is independent of any particular process path, i.e., it is independent of the system history. If a system undergoes a thermodynamic cycle, whether it becomes warmer, cooler, larger, or smaller, then it will have the same amount of energy each time it returns to a particular state. Mathematically speaking, energy is a state function and infinitesimal changes in the energy are exact differentials.
All laws of thermodynamics but the First are statistical and simply describe the tendencies of macroscopic systems. For microscopic systems with few particles, the variations in the parameters become larger than the parameters themselves, and the assumptions of thermodynamics become meaningless. The First Law, i.e. the law of conservation, has become the most secure of all basic laws of science. At present, it is unquestioned.
Second law
Main article: Second law of thermodynamics
“ There is no process that, operating in a cycle, produces no other effect than the subtraction of a positive amount of heat from a reservoir and the production of an equal amount of work. ”
This version is the so-called Kelvin-Planck Statement. In a simple manner, the Second Law states that energy systems have a tendency to increase their entropy (heat transformation content) rather than decrease it.
The entropy of a thermally isolated macroscopic system never decreases (see Maxwell's demon), however a microscopic system may exhibit fluctuations of entropy opposite to that dictated by the Second Law (see Fluctuation Theorem). In fact, the mathematical proof of the Fluctuation Theorem from time-reversible dynamics and the Axiom of Causality, constitutes a proof of the Second Law. In a logical sense the Second Law thus ceases to be a "Law" of Physics and instead becomes a theorem which is valid for large systems or long times.
Stephen Hawking described this using time as an entropy base. For example, when time moves in a forward direction and one, say, breaks a cup of coffee on the floor, no matter what happens, in our universe, one will never see the cup reform. Cups are breaking all the time, but never reforming. Since the Big Bang, the entropy of the universe has been on the rise, and so the Second Law states that this process will continue to increase.
Third law
Main article: Third law of thermodynamics
“ As temperature approaches absolute zero, the entropy of a system approaches a constant. ”
The Third Law says that constant is in fact zero. As the temperature approaches zero, the probability that the system, however complex, sits in its unique quantum ground state approaches one. The entropy of any unique state is zero, so the entropy approaches zero. More rigorously, if the system happens to have half-integer net spin, there are two degenerate ground states, related by time-reversal symmetry, so the dimensionless entropy approaches the natural log of two. However, that is the entropy for the whole system, and is negligible on the scale of any macroscopic system. Basically, no system can reach absolute zero.
参考资料：http://en.wikipedia.org/wiki/Laws_of_thermodynamics
本回答被网友采纳第2个回答 2007-02-10
The first law of Thermodynamics
The total amount of energy in the universe is constant, energy cannot be created nor destoryed, it can merely be changed from one form to another.
The second law of Thermodynamics
in any transfer of energy from one form to anther, useful energy is lost.
The third law of thermodynamics
the entropy of a system will approach a constant value as the temperature decreases, and that the entropy of a pure crystal will be zero at a certain temperature (absolute zero).
--转自everything2.com本回答被提问者采纳
The total amount of energy in the universe is constant, energy cannot be created nor destoryed, it can merely be changed from one form to another.
The second law of Thermodynamics
in any transfer of energy from one form to anther, useful energy is lost.
The third law of thermodynamics
the entropy of a system will approach a constant value as the temperature decreases, and that the entropy of a pure crystal will be zero at a certain temperature (absolute zero).
--转自everything2.com本回答被提问者采纳
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