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第35行： − + − 第一定律 − − The '''first law of thermodynamics''' is a version of the law of [[conservation of energy]], adapted for [[thermodynamic system]]s. − − The first law of thermodynamics is a version of the law of conservation of energy, adapted for thermodynamic systems. − − − The law of conservation of energy states that the total [[energy]] of an [[isolated system]] is constant; energy can be transformed from one form to another, but can be neither created nor destroyed. − − The law of conservation of energy states that the total energy of an isolated system is constant; energy can be transformed from one form to another, but can be neither created nor destroyed. − − − − For a thermodynamic process without transfer of matter, the first law is often formulated − − For a thermodynamic process without transfer of matter, the first law is often formulated − − − ::<math>\Delta U_{\rm system} = Q - W</math>,+ − − − − where {{math|Δ''U''<sub>system</sub>}} denotes the change in the [[internal energy]] of a [[Thermodynamic system#Closed system|closed system]], {{math|''Q''}} denotes the quantity of energy supplied ''to'' the system as [[heat]], and {{math|''W''}} denotes the amount of [[Work (thermodynamics)|thermodynamic work]] (expressed here with a negative sign) done ''by'' the system on its surroundings. (An [[First law of thermodynamics#Sign conventions|alternate sign convention]] not used in this article is to define {{math|''W''}} as the work done ''on'' the system.) − − where denotes the change in the internal energy of a closed system, denotes the quantity of energy supplied to the system as heat, and denotes the amount of thermodynamic work (expressed here with a negative sign) done by the system on its surroundings. (An alternate sign convention not used in this article is to define as the work done on the system.) − − − − − − − − In the case of a two-stage [[thermodynamic cycle]] of a closed system, which returns to its original state, the heat {{math|''Q<sub>in</sub>''}} supplied to the system in one stage of the cycle, minus the heat {{math|''Q<sub>out</sub>''}} removed from it in the other stage, plus the [[Work (thermodynamics)|thermodynamic work]] added to the system, {{math|''W<sub>in</sub>''}}, equals the thermodynamic work that leaves the system {{math|''W<sub>out</sub>''}}. − − In the case of a two-stage thermodynamic cycle of a closed system, which returns to its original state, the heat supplied to the system in one stage of the cycle, minus the heat removed from it in the other stage, plus the thermodynamic work added to the system, , equals the thermodynamic work that leaves the system . − − 在封闭系统的两级'''<font color="#ff8000"> 热力循环thermodynamic cycle</font>'''中，该循环回到其原始状态，在循环的一个阶段向系统提供的热量{{math|''Q<sub>in</sub>''}}，减去另一个阶段从系统中去除的热量{{math|''Q<sub>out</sub>''}}，加上对系统做的的热力学功{{math|''W<sub>in</sub>''}}，等于离开系统的做的热力学功{{math|''W<sub>out</sub>''}}。 + + + − − ::<math>\Delta U_{\rm system\,(full\,cycle)}=0</math> − − − − hence, for a full cycle, − − hence, for a full cycle, − − − ::Or <math>Q - W = Q_{\rm in} - Q_{\rm out} - (W_{\rm out} - W_{\rm in}) =0</math>. − − − − For the particular case of a thermally isolated system (adiabatically isolated), the change of the internal energy of an adiabatically isolated system can only be the result of the work added to the system, because the adiabatic assumption is: {{math|''Q'' {{=}} 0}}. − − For the particular case of a thermally isolated system (adiabatically isolated), the change of the internal energy of an adiabatically isolated system can only be the result of the work added to the system, because the adiabatic assumption is: 0}}. − − − − ::<math>\Delta U_{\rm system} = U_{\rm final} - U_{\rm initial} = W_{\rm in} - W_{\rm out} </math> − − − − − For processes that include transfer of matter, a further statement is needed: 'With due account of the respective fiducial reference states of the systems, when two systems, which may be of different chemical compositions, initially separated only by an impermeable wall, and otherwise isolated, are combined into a new system by the thermodynamic operation of removal of the wall, then − − For processes that include transfer of matter, a further statement is needed: 'With due account of the respective fiducial reference states of the systems, when two systems,'''<font color="#32CD32">which may be of different chemical compositions, initially separated only by an impermeable wall, and otherwise isolated, are combined into a new system by the thermodynamic operation of removal of the wall</font>''', then − − 对于包括物质转移的过程，还需要进一步的说明: ‘在充分考虑了各个系统的基准参考状态后，当两个系统---- '''<font color="#32CD32">它们可能由不同的化学成分组成，最初只是被防渗墙隔开，或者是被隔离---- 通过移除墙体的热力学操作结合成一个新系统</font>'''，那么 + + + − − ::<math>U_{\rm system} = U_1 + U_2</math>, − − − − − where {{math|''U''<sub>system</sub>}} denotes the internal energy of the combined system, and {{math|''U''<sub>1</sub>}} and {{math|''U''<sub>2</sub>}} denote the internal energies of the respective separated systems.' − − where denotes the internal energy of the combined system, and and denote the internal energies of the respective separated systems.' − − − The First Law encompasses several principles: − − The First Law encompasses several principles: − * The [[Conservation of energy|law of conservation of energy]]. − − ::This states that energy can be neither created nor destroyed. However, energy can change forms, and energy can flow from one place to another. A particular consequence of the law of conservation of energy is that the total energy of an isolated system does not change. − − ::This states that energy can be neither created nor destroyed. However, energy can change forms, and energy can flow from one place to another. A particular consequence of the law of conservation of energy is that the total energy of an isolated system does not change. − * The concept of [[internal energy]] and its relationship to temperature.<br> − − ::If a system has a definite temperature, then its total energy has three distinguishable components. If the system is in motion as a whole, it has [[kinetic energy]]. If the system as a whole is in an externally imposed force field (e.g. gravity), it has [[potential energy]] relative to some reference point in space. Finally, it has internal energy, which is a fundamental quantity of thermodynamics. The establishment of the concept of internal energy distinguishes the first law of thermodynamics from the more general law of conservation of energy. − − ::If a system has a definite temperature, then its total energy has three distinguishable components. If the system is in motion as a whole, it has kinetic energy. If the system as a whole is in an externally imposed force field (e.g. gravity), it has potential energy relative to some reference point in space. Finally, it has internal energy, which is a fundamental quantity of thermodynamics. The establishment of the concept of internal energy distinguishes the first law of thermodynamics from the more general law of conservation of energy. − − − ::<math>E_{\rm total} = \mathrm{KE}_{\rm system} + \mathrm{PE}_{\rm system} + U_{\rm system}</math> − − − ::The internal energy of a substance can be explained as the sum of the diverse kinetic energies of the erratic microscopic motions of its constituent atoms, and of the potential energy of interactions between them. Those microscopic energy terms are collectively called the substance's internal energy, {{math|''U''}}, and are accounted for by macroscopic thermodynamic property. The total of the kinetic energies of microscopic motions of the constituent atoms increases as the system's temperature increases; this assumes no other interactions at the microscopic level of the system such as chemical reactions, potential energy of constituent atoms with respect to each other. − − ::The internal energy of a substance can be explained as the sum of the diverse kinetic energies of the erratic microscopic motions of its constituent atoms, and of the potential energy of interactions between them. Those microscopic energy terms are collectively called the substance's internal energy, , and are accounted for by macroscopic thermodynamic property. The total of the kinetic energies of microscopic motions of the constituent atoms increases as the system's temperature increases; this assumes no other interactions at the microscopic level of the system such as chemical reactions, potential energy of constituent atoms with respect to each other. − * [[Work (physics)|Work]] is a process of transferring energy to or from a system in ways that can be described by macroscopic mechanical forces exerted by factors in the surroundings, outside the system. '''<font color="#32CD32">Examples are an externally driven shaft agitating a stirrer within the system, or an externally imposed electric field that polarizes the material of the system, or a piston that compresses the system.</font>''' Unless otherwise stated, it is customary to treat work as occurring without its [[dissipation]] to the surroundings. Practically speaking, in all natural process, some of the work is dissipated by internal friction or viscosity. The work done by the system can come from its overall kinetic energy, from its overall potential energy, or from its internal energy. − − − ::For example, when a machine (not a part of the system) lifts a system upwards, some energy is transferred from the machine to the system. The system's energy increases as work is done on the system and in this particular case, the energy increase of the system is manifested as an increase in the system's [[gravitational potential energy]]. Work added to the system increases the Potential Energy of the system: − − ::For example, when a machine (not a part of the system) lifts a system upwards, some energy is transferred from the machine to the system. The system's energy increases as work is done on the system and in this particular case, the energy increase of the system is manifested as an increase in the system's gravitational potential energy. Work added to the system increases the Potential Energy of the system: − − − − :::<math>W = \Delta \mathrm{PE}_{\rm system}</math> − − − − ::Or in general, the energy added to the system in the form of work can be partitioned to kinetic, potential or internal energy forms: − − ::Or in general, the energy added to the system in the form of work can be partitioned to kinetic, potential or internal energy forms: − − − :::<math>W = \Delta \mathrm{KE}_{\rm system}+\Delta \mathrm{PE}_{\rm system}+\Delta U_{\rm system}</math> − − − − * When matter is transferred into a system, that masses' associated internal energy and potential energy are transferred with it.<br> − − − − :::<math>\left( u \,\Delta M \right)_{\rm in} = \Delta U_{\rm system}</math> − − − − ::where {{math|''u''}} denotes the internal energy per unit mass of the transferred matter, as measured while in the surroundings; and {{math|Δ''M''}} denotes the amount of transferred mass. − − ::where {{math|''u''}} denotes the internal energy per unit mass of the transferred matter, as measured while in the surroundings; and denotes the amount of transferred mass. − * The flow of [[heat]] is a form of energy transfer.<br> − − ::Heating is a natural process of moving energy to or from a system other than by work or the transfer of matter. Direct passage of heat is only from a hotter to a colder system. − − ::Heating is a natural process of moving energy to or from a system other than by work or the transfer of matter. Direct passage of heat is only from a hotter to a colder system. − − − − ::If the system has rigid walls that are impermeable to matter, and consequently energy cannot be transferred as work into or out from the system, and no external long-range force field affects it that could change its internal energy, then the internal energy can only be changed by the transfer of energy as heat: − − ::If the system has rigid walls that are impermeable to matter, and consequently energy cannot be transferred as work into or out from the system, and no external long-range force field affects it that could change its internal energy, then the internal energy can only be changed by the transfer of energy as heat: − − − − ::<math>\Delta U_{\rm system}=Q</math> − − − − ::where {{math|''Q''}} denotes the amount of energy transferred into the system as heat. − − ::where {{math|''Q''}} denotes the amount of energy transferred into the system as heat. − − − − Combining these principles leads to one traditional statement of the first law of thermodynamics: it is not possible to construct a machine which will perpetually output work without an equal amount of energy input to that machine. Or more briefly, a perpetual motion machine of the first kind is impossible. − − Combining these principles leads to one traditional statement of the first law of thermodynamics: it is not possible to construct a machine which will perpetually output work without an equal amount of energy input to that machine. Or more briefly, a perpetual motion machine of the first kind is impossible.
→First law
虽然这些关于温度和热平衡的概念是热力学的基础，并在19世纪得到了清楚的阐述，但是直到20世纪30年代福勒和古根海姆这样做的时候，人们才普遍感觉到需要对上述定律进行明确编号，而这时第一定律、第二定律和第三定律已经得到广泛的理解和认可。因此，它被称为第零定律。该定律作为早期定律基础的重要性在于，它允许以非循环的方式定义温度，而无需参考熵及其共轭变量。这样的温度定义被称为“经验主义的”。<ref>Adkins, C.J. (1968/1983). ''Equilibrium Thermodynamics'', (first edition 1968), third edition 1983, Cambridge University Press, {{ISBN|0-521-25445-0}}, pp. 18–20.</ref><ref>Bailyn, M. (1994). ''A Survey of Thermodynamics'', American Institute of Physics Press, New York, {{ISBN|0-88318-797-3}}, p. 26.</ref><ref>Buchdahl, H.A. (1966), ''The Concepts of Classical Thermodynamics'', Cambridge University Press, London, pp. 30, 34ff, 46f, 83.</ref><ref>*Münster, A. (1970), ''Classical Thermodynamics'', translated by E.S. Halberstadt, Wiley–Interscience, London, {{ISBN|0-471-62430-6}}, p. 22.</ref><ref>[[Brian Pippard|Pippard, A.B.]] (1957/1966). ''Elements of Classical Thermodynamics for Advanced Students of Physics'', original publication 1957, reprint 1966, Cambridge University Press, Cambridge, p. 10.</ref><ref>[[Harold A. Wilson (physicist)|Wilson, H.A.]] (1966). ''Thermodynamics and Statistical Mechanics'', Cambridge University Press, London, pp. 4, 8, 68, 86, 97, 311.</ref>
虽然这些关于温度和热平衡的概念是热力学的基础，并在19世纪得到了清楚的阐述，但是直到20世纪30年代福勒和古根海姆这样做的时候，人们才普遍感觉到需要对上述定律进行明确编号，而这时第一定律、第二定律和第三定律已经得到广泛的理解和认可。因此，它被称为第零定律。该定律作为早期定律基础的重要性在于，它允许以非循环的方式定义温度，而无需参考熵及其共轭变量。这样的温度定义被称为“经验主义的”。<ref>Adkins, C.J. (1968/1983). ''Equilibrium Thermodynamics'', (first edition 1968), third edition 1983, Cambridge University Press, {{ISBN|0-521-25445-0}}, pp. 18–20.</ref><ref>Bailyn, M. (1994). ''A Survey of Thermodynamics'', American Institute of Physics Press, New York, {{ISBN|0-88318-797-3}}, p. 26.</ref><ref>Buchdahl, H.A. (1966), ''The Concepts of Classical Thermodynamics'', Cambridge University Press, London, pp. 30, 34ff, 46f, 83.</ref><ref>*Münster, A. (1970), ''Classical Thermodynamics'', translated by E.S. Halberstadt, Wiley–Interscience, London, {{ISBN|0-471-62430-6}}, p. 22.</ref><ref>[[Brian Pippard|Pippard, A.B.]] (1957/1966). ''Elements of Classical Thermodynamics for Advanced Students of Physics'', original publication 1957, reprint 1966, Cambridge University Press, Cambridge, p. 10.</ref><ref>[[Harold A. Wilson (physicist)|Wilson, H.A.]] (1966). ''Thermodynamics and Statistical Mechanics'', Cambridge University Press, London, pp. 4, 8, 68, 86, 97, 311.</ref>
==First law==
==第一定律 First law==
热力学第一定律是'''<font color="#ff8000"> 能量守恒 conservation of energy</font>'''定律的一个版本，适用于热力学系统。
热力学第一定律是'''<font color="#ff8000"> 能量守恒 conservation of energy</font>'''定律的一个版本，适用于热力学系统。
能量守恒定律指出，一个孤立系统的总能量是恒定的;能量可以从一种形式转化为另一种形式，但能量既不会凭空产生也不会凭空消失。
能量守恒定律指出，一个孤立系统的总能量是恒定的;能量可以从一种形式转化为另一种形式，但能量既不会凭空产生也不会凭空消失。
对于一个没有物质转移的热力学过程，第一定律通常用公式表示为：
对于一个没有物质转移的热力学过程，第一定律通常用公式表示为：
::<math>\Delta U_{\rm system} = Q - W</math>,
::<math>\Delta U_{\rm system} = Q - W</math>,
其中{{math|Δ''U''<sub>system</sub>}}表示一个封闭系统内部能量的变化，{{math|''Q''}} 表示外界以热的形式提供给系统的能量，{{math|''W''}}表示该系统对周围环境所做的热力学功(在这里用负号表示)。
其中{{math|Δ''U''<sub>system</sub>}}表示一个封闭系统内部能量的变化，{{math|''Q''}} 表示外界以热的形式提供给系统的能量，{{math|''W''}}表示该系统对周围环境所做的热力学功(在这里用负号表示)。(定义对系统所做的功在本文中没有使用的另一个符号约定。)
(定义对系统所做的功在本文中没有使用的另一个符号约定。)
在封闭系统的两级'''<font color="#ff8000"> 热力循环thermodynamic cycle</font>'''中，该循环回到其原始状态，在循环的一个阶段向系统提供的热量{{math|''Q<sub>in</sub>''}}，减去另一个阶段从系统中去除的热量{{math|''Q<sub>out</sub>''}}，加上对系统做的的热力学功{{math|''W<sub>in</sub>''}}，
等于离开系统的做的热力学功{{math|''W<sub>out</sub>''}}。
::<math>\Delta U_{\rm system\,(full\,cycle)}=0</math>
::<math>\Delta U_{\rm system\,(full\,cycle)}=0</math>
因此，对于一个完整的循环,
因此，对于一个完整的循环,
::Or <math>Q - W = Q_{\rm in} - Q_{\rm out} - (W_{\rm out} - W_{\rm in}) =0</math>.
::Or <math>Q - W = Q_{\rm in} - Q_{\rm out} - (W_{\rm out} - W_{\rm in}) =0</math>.
对于绝热系统（绝热隔离）的特殊情况，绝热隔离系统内能的变化只能是系统做功的结果，因为绝热假设是: {{math|''Q'' {{=}} 0}}。
对于绝热系统（绝热隔离）的特殊情况，绝热隔离系统内能的变化只能是系统做功的结果，因为绝热假设是: {{math|''Q'' {{=}} 0}}。
::<math>\Delta U_{\rm system} = U_{\rm final} - U_{\rm initial} = W_{\rm in} - W_{\rm out} </math>
::<math>\Delta U_{\rm system} = U_{\rm final} - U_{\rm initial} = W_{\rm in} - W_{\rm out} </math>
对于包括物质转移的过程，还需要进一步的说明: ‘在充分考虑了各个系统的基准参考状态后，当两个系统----
'''<font color="#32CD32">它们可能由不同的化学成分组成，最初只是被防渗墙隔开，或者是被隔离---- 通过移除墙体的热力学操作结合成一个新系统</font>'''，
那么
::<math>U_{\rm system} = U_1 + U_2</math>,
::<math>U_{\rm system} = U_1 + U_2</math>,
其中{{math|''U''<sub>system</sub>}}表示组合系统的内能，{{math|''U''<sub>1</sub>}} and {{math|''U''<sub>2</sub>}} 表示各自分离系统的内能
其中{{math|''U''<sub>system</sub>}}表示组合系统的内能，{{math|''U''<sub>1</sub>}} and {{math|''U''<sub>2</sub>}} 表示各自分离系统的内能
第一定律包括以下几个原则:
第一定律包括以下几个原则:
* 能量守恒定律
* 能量守恒定律
::能量既不能被创造也不能被消灭。但是，能量可以改变形式，能量可以从一个地方流动到另一个地方。能量守恒定律的一个特殊结果是，孤立系统的总能量不变。
::能量既不能被创造也不能被消灭。但是，能量可以改变形式，能量可以从一个地方流动到另一个地方。能量守恒定律的一个特殊结果是，孤立系统的总能量不变。
* 内能的概念及其与温度关系。
* 内能的概念及其与温度关系。
::如果系统具有确定的温度，则其总能量具有三个可区分的成分，分别称为动能（由与系统整体运动产生的能量），势能（由外部施加的立场产生的能量，比如重力）和内能（热热力学的基本量）。内能概念的确立将热力学第一定律与一般的能量守恒定律区分开来。
::如果系统具有确定的温度，则其总能量具有三个可区分的成分，分别称为动能（由与系统整体运动产生的能量），势能（由外部施加的立场产生的能量，比如重力）和内能（热热力学的基本量）。内能概念的确立将热力学第一定律与一般的能量守恒定律区分开来。
——Solitude(讨论)
——Solitude(讨论)
::<math>E_{\rm total} = \mathrm{KE}_{\rm system} + \mathrm{PE}_{\rm system} + U_{\rm system}</math>
::<math>E_{\rm total} = \mathrm{KE}_{\rm system} + \mathrm{PE}_{\rm system} + U_{\rm system}</math>
::物质的内能可以解释为其组成原子的不规则微观运动的不同动能和它们之间相互作用的势能的总和。这些微观能量统称为物质的内能，并由宏观热力学性质来解释。组成原子的微观运动的总和随着系统温度的升高而增加; 这假设在系统的微观层次上没有其他的相互作用，例如化学反应、组成原子相互间的势能。
::物质的内能可以解释为其组成原子的不规则微观运动的不同动能和它们之间相互作用的势能的总和。这些微观能量统称为物质的内能，并由宏观热力学性质来解释。组成原子的微观运动的总和随着系统温度的升高而增加; 这假设在系统的微观层次上没有其他的相互作用，例如化学反应、组成原子相互间的势能。
* 做功是一种以某种方式向系统传递能量或从系统传递能量的过程，其方式可以用作用在系统外部及其周围环境之间的宏观机械力来描述。'''<font color="#32CD32">例如，外部驱动的轴在系统内搅动，或外部施加的电场使系统材料极化，或活塞压缩系统。</font>'''除非另有说明，习惯上把做功看作是在不影响周围环境的情况下发生的。实际上，在一切自然过程中，有些功是因内摩擦或粘黏而消失的。系统所做的功，可以来自于它的总动能，总势能或者它的内能。
* 做功是一种以某种方式向系统传递能量或从系统传递能量的过程，其方式可以用作用在系统外部及其周围环境之间的宏观机械力来描述。'''<font color="#32CD32">例如，外部驱动的轴在系统内搅动，或外部施加的电场使系统材料极化，或活塞压缩系统。</font>'''除非另有说明，习惯上把做功看作是在不影响周围环境的情况下发生的。实际上，在一切自然过程中，有些功是因内摩擦或粘黏而消失的。系统所做的功，可以来自于它的总动能，总势能或者它的内能。
::例如，当一台机器(不是系统的一部分)将系统向上提升时，一些能量就会从机器转移到系统。系统的能量随着系统所做功的增加而增加，在这种特殊的情况下，系统的能量增加表现为系统的重力势能的增加。机器将系统向上提升时对系统做的功增加了系统的势能:
::例如，当一台机器(不是系统的一部分)将系统向上提升时，一些能量就会从机器转移到系统。系统的能量随着系统所做功的增加而增加，在这种特殊的情况下，系统的能量增加表现为系统的重力势能的增加。机器将系统向上提升时对系统做的功增加了系统的势能:
:::<math>W = \Delta \mathrm{PE}_{\rm system}</math>
:::<math>W = \Delta \mathrm{PE}_{\rm system}</math>
::或者一般来说，以功的形式加入系统的能量可以分为动能、势能或内能:
::或者一般来说，以功的形式加入系统的能量可以分为动能、势能或内能:
:::<math>W = \Delta \mathrm{KE}_{\rm system}+\Delta \mathrm{PE}_{\rm system}+\Delta U_{\rm system}</math>
:::<math>W = \Delta \mathrm{KE}_{\rm system}+\Delta \mathrm{PE}_{\rm system}+\Delta U_{\rm system}</math>
* 当物质转移到一个系统中时，物质相关的内能和势能也随之转移。
* 当物质转移到一个系统中时，物质相关的内能和势能也随之转移。
:::<math>\left( u \,\Delta M \right)_{\rm in} = \Delta U_{\rm system}</math>
:::<math>\left( u \,\Delta M \right)_{\rm in} = \Delta U_{\rm system}</math>
::其中{{math|''u''}}表示在周围环境中测量的转移物质的单位质量的内能; {{math|Δ''M''}}表示被转移物质的数量。
::其中{{math|''u''}}表示在周围环境中测量的转移物质的单位质量的内能; {{math|Δ''M''}}表示被转移物质的数量。
* 热的流动是能量传递的一种形式。
* 热的流动是能量传递的一种形式。
::加热是一个将能量转移到系统中或从系统中转移出的自然过程，而不是通过做功或物质的转移。热量只能从较热的系统直接传递到较冷的系统。
::加热是一个将能量转移到系统中或从系统中转移出的自然过程，而不是通过做功或物质的转移。热量只能从较热的系统直接传递到较冷的系统。
::如果系统具有不渗透物质的刚性壁，那么能量不能通过做功传入或传出系统，而且没有外部的远程力场影响系统以改变其内能，那么内能只能通过以热的形式进行传递来改变:
::如果系统具有不渗透物质的刚性壁，那么能量不能通过做功传入或传出系统，而且没有外部的远程力场影响系统以改变其内能，那么内能只能通过以热的形式进行传递来改变:
::<math>\Delta U_{\rm system}=Q</math>
::<math>\Delta U_{\rm system}=Q</math>
::其中{{math|''Q''}}表示以热量形式传递到系统中的能量。
::其中{{math|''Q''}}表示以热量形式传递到系统中的能量。
结合这些原理，就可以得出传统的热力学第一定律的表述: 不可能制造一台在没有等量能量输入的情况下不断做功的机器。或者更简单地说，第一类永动机是不可能造成的。
结合这些原理，就可以得出传统的热力学第一定律的表述: 不可能制造一台在没有等量能量输入的情况下不断做功的机器。或者更简单地说，第一类永动机是不可能造成的。