Method
Laws of thermodynamics
Overview
The laws of thermodynamics are a set of scientific laws which define a group of physical quantities, such as temperature, energy, and entropy, that characterize thermodynamic systems in thermodynamic equilibrium. The laws also use various parameters for thermodynamic processes, such as thermodynamic work and heat, and establish relationships between them. They state empirical facts that form a basis of precluding the possibility of certain phenomena, such as perpetual motion. In addition to their use in thermodynamics, they are important fundamental laws of physics in general and are applicable in other natural sciences.
Traditionally, thermodynamics has recognized three fundamental laws, simply named by an ordinal identification, the first law, the second law, and the third law. A more fundamental statement was later labelled as the zeroth law after the first three laws had been established.
The zeroth law of thermodynamics defines thermal equilibrium and forms a basis for the definition of temperature: if two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other.
The first law of thermodynamics states that, when energy passes into or out of a system (as work, heat, or matter), the system's internal energy changes in accordance with the law of conservation of energy. This also results in the observation that, in an externally isolated system, even with internal changes, the sum of all forms of energy must remain constant, as energy cannot be created or destroyed.
The second law of thermodynamics states that in a natural thermodynamic process, the sum of the entropies of the interacting thermodynamic systems never decreases. A common corollary of the statement is that heat does not spontaneously pass from a colder body to a warmer body.
The third law of thermodynamics states that a system's entropy approaches a constant value as the temperature approaches absolute zero. With the exception of non-crystalline solids (glasses), the entropy of a system at absolute zero is typically close to zero.
The first and second laws prohibit two kinds of perpetual motion machines, respectively: the perpetual motion machine of the first kind which produces work with no energy input, and the perpetual motion machine of the second kind which spontaneously converts thermal energy into mechanical work.
Overview adapted from Wikipedia (CC BY-SA 4.0; see the article history for authors).
Possible passages
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This sort of following we call _resulting_; the first of the states being named a _cause_, the second an _effect_. When a substance takes fire, for instance, this state of ignition must have been preceded by a state, 1^o, of affinity to oxygen; 2^o, of contact with oxygen; 3^o, of a given temperature. Now, as ignition must necessarily follow immediately upon this state, and as it has only just taken place, that…
Arthur Schopenhauer, On the Fourfold Root of the Principle of Sufficient Reason, and On the Will in Nature
States what Laws of thermodynamics is.
If we knew, therefore, the three simple laws, but had never tried the Torricellian experiment, we might _deduce_ its result from those laws. The known weight of the air, combined with the position of the apparatus, would bring the mercury within the first of the three inductions; the first induction would bring it within the second, and the second within the third, in the manner which we characterized in treating of…
John Stuart Mill, A System of Logic
States what Laws of thermodynamics is.
This dissipated heat is called latent. It is transformed, by cooling the steam, into water again, and the water into ice, so the same mass of heat which was formerly latent, is again set free, that is, as heat capable of being felt and measured. This setting free of heat by the condensation of steam and the freezing of water is the reason that steam if it is cooled off at 100 deg.
Friedrich Engels, Landmarks of Scientific Socialism
States what Laws of thermodynamics is.
Related ideas
- Second law of thermodynamics
- London
- Heat
- Matter
- Physics
- Scientific law
- Science
- Statistical mechanics
- Thermodynamics
- Lord Kelvin
- Conservation of energy
- Encyclopædia Britannica
- Energy
- Entropy
Place in the tradition
Part of Ecological economics.