Cecily Zamora
The first law of thermodynamics, which states that energy cannot be created or destroyed, was formulated in the 19th century. The original statements of the first law appeared in a conceptual framework that defined the transfer of energy as heat. The first explicit statement of the law was made by Rudolf Clausius in 1850, though other scientists, including Germain Hess, Julius Robert von Mayer, and James Prescott Joule, made contributions to the development of the law.
| Characteristics | Values |
|---|---|
| Name of Scientist | Rudolf Clausius and William Thomson (Kelvin) |
| Year of Discovery | 1850 |
| Other Contributors | James Prescott Joule, Sadi Carnot, Hermann von Helmholtz, Germain Hess, Julius Robert von Mayer |
| Law Statement | The total energy of an isolated system is constant; energy cannot be created or destroyed, but it can be transformed from one form to another |
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What You'll Learn
The first explicit statement of the first law
The first law of thermodynamics is a formulation of the law of conservation of energy in the context of thermodynamic processes. It distinguishes two principal forms of energy transfer: heat and thermodynamic work. The law also defines the internal energy of a system, an extensive property that accounts for the balance of heat transfer, thermodynamic work, and matter transfer into and out of the system.
Energy cannot be created or destroyed but can be transformed from one form to another. In an externally isolated system with internal changes, the sum of all forms of energy remains constant. This implies that perpetual motion machines of the first kind are impossible. Work done by a system on its surroundings requires the consumption of the system's internal energy, which must be resupplied as heat by an external energy source.
The original 19th-century statements of the first law appeared in a conceptual framework that took the transfer of energy as heat as a primitive notion, defined by calorimetry. This framework also considered the transfer of energy as work, but it did not presume a general concept of energy. Instead, it regarded energy as derived or synthesized from the prior notions of heat and work.
While Rudolf Clausius made the first explicit statement of the first law, it was believed to have been developed almost simultaneously by Julius Robert Mayer and James Prescott Joule in the 1840s. However, James Watt had laid down the foundations for the first law in his 1769 patent, which was published in 1774.
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Rudolf Clausius
In 1840, Clausius entered the University of Berlin, but it is unclear which subjects he initially intended to pursue. He would later go on to become a professor of physics, first at the Artillery and Engineering School in Berlin in 1850, then at Zürich Polytechnikum in 1855, and later at the University of Würzburg in 1867 and the University of Bonn in 1869.
Clausius is best known for his work in thermodynamics, specifically his formulation of the first and second laws of thermodynamics. In 1850, he presented a paper titled "On the Moving Force of Heat and the Laws of Heat which may be Deduced Therefrom," in which he made the first explicit statement of the first law of thermodynamics. This law, also known as the law of conservation of energy, establishes that energy cannot be created or destroyed, only transformed from one form to another. Clausius expressed this law in the context of cyclic thermodynamic processes and the concept of internal energy.
In addition to his work on the first law, Clausius also made important contributions to the second law of thermodynamics. He presented a well-known statement of this law in 1850, which was later published in German in 1854 and in English in 1856: "Heat cannot of itself pass from a colder to a hotter body." Clausius also contributed to the field of kinetic theory and introduced the concept of 'Mean free path' of a particle.
Clausius received numerous honours and awards for his work, including being elected a Fellow of the Royal Society of London in 1868 and receiving the Copley Medal in 1879. He also served in the Franco-Prussian War, organizing an ambulance corps and receiving the Iron Cross for his services.
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William Thomson (Kelvin)
The first law of thermodynamics is a formulation of the law of conservation of energy in the context of thermodynamic processes. While the original 19th-century statements of the first law appeared in a conceptual framework, the first explicit statement of the first law of thermodynamics was made by Rudolf Clausius in 1850. However, the law was also formally stated by Scottish physicist William Thomson (Kelvin) around 1860.
William Thomson, also known as Lord Kelvin, was a mathematical physicist and engineer from Belfast, Ireland (now Northern Ireland), then part of the United Kingdom. He is known for his work on the mathematical analysis of electricity and formulation of the laws of thermodynamics, which led to him being ennobled as Baron Kelvin in 1892.
Thomson's work on the first law of thermodynamics was part of his broader work on the mathematical analysis of electricity. He was interested in the relationship between heat, work, temperature, and energy, which would become the foundation of the field of thermodynamics. Thomson's work on the first law of thermodynamics established the concept of internal energy and the two principal forms of energy transfer: heat and thermodynamic work.
Thomson's statement of the first law of thermodynamics was made in conjunction with Clausius' work. While Clausius focused on cyclic thermodynamic processes and the existence of a function of state of the system, Thomson's work contributed to the understanding of the internal energy of a system and the balance of heat transfer, work, and matter transfer into and out of the system.
In summary, William Thomson (Kelvin) was a key figure in the development of the first law of thermodynamics, which established the fundamental principles of energy conservation and transfer in the context of thermodynamic processes. His work, along with that of Clausius, laid the foundation for the field of thermodynamics and contributed to our understanding of energy and its transformations.
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The law of conservation of energy
The first law of thermodynamics is a formulation of the law of conservation of energy in the context of thermodynamic processes. The law was first formulated in 1850 by Rudolf Clausius and William Thomson (Kelvin). However, the groundwork for this law was laid down by several other scientists in the preceding years. For instance, in 1840, Germain Hess stated Hess's law, a conservation law for the heat of reaction during chemical transformations. This was later recognised as a consequence of the first law of thermodynamics. In 1842, Julius Robert von Mayer made a statement that was interpreted as indicating that heat and work are interconvertible in a process at constant pressure. Also in 1842, James Prescott Joule, an English physicist, measured the mechanical equivalent of heat, establishing that various forms of energy are the same and can be converted into one another.
The first law of thermodynamics states that energy cannot be created or destroyed, only transformed from one form to another. This principle is also known as the law of conservation of energy. According to this law, for a closed system undergoing a thermodynamic cycle, the change in internal energy of the system is the sum of all the energy inputs and outputs to and from the system. In other words, the internal energy of a system is equal to the work done on the system, plus or minus the heat that flows in or out of the system and any other work done on the system. This can be expressed mathematically as ΔU = Q - W, where ΔU is the change in internal energy, Q is the heat added to the system, and W is the work done by the system.
The first law of thermodynamics distinguishes two principal forms of energy transfer in a thermodynamic process affecting a thermodynamic system without the transfer of matter: heat and thermodynamic work. The law also defines the internal energy of a system, an extensive property that accounts for the balance of heat transfer, thermodynamic work, and matter transfer into and out of the system.
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Perpetual motion machines
The first law of thermodynamics, formulated in 1850 by Rudolf Clausius, is a law of energy conservation in the context of thermodynamic processes. It states that energy cannot be created or destroyed, only transformed from one form to another. This law of conservation of energy is central to the concept of perpetual motion machines, which are hypothetical machines that can perform work indefinitely without an external energy source.
Despite the long history of attempts to create perpetual motion machines, they are considered impossible by the scientific community. This impossibility arises from the fact that such machines would violate the first and/or second laws of thermodynamics. The first law, as mentioned, states that energy cannot be created or destroyed, implying that a perpetual motion machine of the first kind, which produces work without energy input, is impossible. The second law of thermodynamics states that an isolated system will move towards a state of disorder, with an increase in entropy (lost energy) as energy is transformed. This implies that a perpetual motion machine of the second kind, which spontaneously converts thermal energy into mechanical work, is also impossible, as it would require perfect efficiency with no energy wasted.
There is also a classification of perpetual motion machines of the third kind, which refers to machines that eliminate friction and other dissipative forces to maintain motion forever due to their mass inertia. However, this type of machine is also impossible, as it is mathematically proven that dissipation can never be entirely eliminated in a mechanical system.
While perpetual motion machines in the traditional sense are impossible, there have been discoveries that challenge our understanding. For example, the discovery of time crystals in 2016 exhibited atomic motion without energy loss, satisfying the definition of perpetual motion on a microscopic scale. Nevertheless, these systems do not violate thermodynamic laws because they are in their quantum ground state, and no energy can be extracted from them.
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Frequently asked questions
Around 1850, Rudolf Clausius and William Thomson (Kelvin) developed the first law of thermodynamics.
The first law of thermodynamics is a formulation of the law of conservation of energy in the context of thermodynamic processes. It distinguishes two principal forms of energy transfer: heat and thermodynamic work. It also defines the internal energy of a system, taking into account the balance of heat transfer, thermodynamic work, and matter transfer.
The first law is expressed as ΔU = Q - W, where ΔU is the change in internal energy, Q is the heat added to the system, and W is the work done by the system.
The first law states that energy cannot be created or destroyed but can only change from one form to another. This implies that the total energy of an isolated system remains constant.
