Mechanical equivalent of heat
Encyclopedia
In the history of science
, the mechanical equivalent of heat was a concept
that had an important part in the development and acceptance of the conservation of energy
and the establishment of the science of thermodynamics
in the 19th century.
The concept stated that motion
and heat
are mutually interchangeable and that in every case, a given amount of work
would generate the same amount of heat, provided the work done is totally converted to heat energy.
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Count Rumford
had observed the frictional heat generated by boring cannon at the arsenal in Munich, Germany circa 1797. Rumford immersed a cannon barrel in water and arranged for a specially blunted boring tool. He showed that the water could be boiled within roughly two and a half hours and that the supply of frictional heat was seemingly inexhaustible. Based on his experiments, he published "An Experimental Enquiry Concerning the Source of the Heat which is Excited by Friction", (1798), Philosophical Transaction of the Royal Society p.102. This was the scientific paper by Benjamin Thompson
, Count Rumford, that provided a substantial challenge to established theories of heat and began the 19th century revolution in thermodynamics. The experiment inspired the work of James Prescott Joule
in the 1840s. Joule's more exact measurements on equivalence were pivotal in establishing the kinetic theory at the expense of the caloric theory. The idea that heat and work are equivalent was also proposed by Julius Robert von Mayer in 1842 in the leading German physics journal and independently by James Prescott Joule in 1843 in the leading British physics journal. Similar work was carried out by Ludwig A. Colding
in 1840-1843, though Colding's work was little known outside his native Denmark. A collaboration between Nicolas Clément and Sadi Carnot
in the 1820s had some related thinking near the same lines. In 1845 Joule published a paper entitled "The Mechanical Equivalent of Heat", in which he specified a numerical value for the amount of mechanical work required to produce a unit of heat. In particular Joule had experimented on the amount of mechanical work generated by friction needed to raise the temperature
of a pound
of water
by one degree Fahrenheit
and found a consistent value of 772.24 foot pound force (4.1550 J
·cal
-1). Joule contended that motion
and heat
were mutually interchangeable and that, in every case, a given amount of work
would generate the same amount of heat. Von Mayer also published a numerical value for mechanical equivalent of heat in 1845 but his experimental method wasn't as convincing.
Though a standardised value of 4.1860 J·cal-1 was established in the early 20th century, in the 1920s, it was ultimately realised that the constant is simply the specific heat of water, a quantity that varies with temperature between the values of 4.17 and 4.22 J·g
-1·°C
-1. The change in unit was the result of the demise of the calorie as a unit in physics and chemistry.
Both von Mayer and Joule met with initial neglect and resistance, despite having published in leading European physics journals. But by 1847 lots of the leading scientists of day were paying attention. Hermann Helmholtz in 1847 published what is considered a definitive declaration of the conservation of energy
. Helmholtz had learned from reading Joule's publications, though Helmholtz eventually came around to crediting both Joule and von Mayer for priority.
Also in 1847, Joule made a well-attended presentation at the annual meeting of British Association for the Advancement of Science
. Among those in attendance was William Thomson
. Thomson was intrigued but initially skeptical. Over the next two years, Thomson became increasingly convinced of Joule's theory, finally admitting his conviction in print in 1851, simultaneously crediting von Mayer. Thomson collaborated with Joule, mainly by correspondence, Joule conducting experiments, Thomson analysing the results and suggesting further experiments. The collaboration lasted from 1852 to 1856. Its published results did much to bring about general acceptance of Joule's work and the kinetic theory
.
However, in 1848, von Mayer had first had sight of Joule's papers and wrote to the French
Académie des Sciences to assert priority. His letter was published in the Comptes Rendus
and Joule was quick to react. Thomson's close relationship with Joule allowed him to become dragged into the controversy. The pair planned that Joule would admit von Mayer's priority for the idea of the mechanical equivalent but to claim that experimental verification rested with Joule. Thomson's associates, co-workers and relatives such as William John Macquorn Rankine
, James Thomson
, James Clerk Maxwell
, and Peter Guthrie Tait
joined to champion Joule's cause.
However, in 1862, John Tyndall
, in one of his many excursions into popular science
and many public disputes with Thomson and his circle, gave a lecture at the Royal Institution
entitled On Force in which he credited von Mayer with conceiving and measuring the mechanical equivalent of heat. Thomson and Tait were angered, and an undignified public exchange of correspondence took place in the pages of the Philosophical Magazine
, and the rather more popular Good Words. Tait even resorted to championing Colding's
cause in an attempt to undermine von Mayer.
Though Tyndall again pressed von Mayer's cause in Heat: A Mode of Motion (1863) with the publication of Sir Henry Enfield Roscoe
's Edinburgh Review
article Thermo-Dynamics in January 1864, Joule's reputation was sealed while that of von Mayer entered a period of obscurity.
History of science
The history of science is the study of the historical development of human understandings of the natural world and the domains of the social sciences....
, the mechanical equivalent of heat was a concept
Concept
The word concept is used in ordinary language as well as in almost all academic disciplines. Particularly in philosophy, psychology and cognitive sciences the term is much used and much discussed. WordNet defines concept: "conception, construct ". However, the meaning of the term concept is much...
that had an important part in the development and acceptance of the conservation of energy
Conservation of energy
The nineteenth century law of conservation of energy is a law of physics. It states that the total amount of energy in an isolated system remains constant over time. The total energy is said to be conserved over time...
and the establishment of the science of thermodynamics
Thermodynamics
Thermodynamics is a physical science that studies the effects on material bodies, and on radiation in regions of space, of transfer of heat and of work done on or by the bodies or radiation...
in the 19th century.
The concept stated that motion
Motion (physics)
In physics, motion is a change in position of an object with respect to time. Change in action is the result of an unbalanced force. Motion is typically described in terms of velocity, acceleration, displacement and time . An object's velocity cannot change unless it is acted upon by a force, as...
and heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
are mutually interchangeable and that in every case, a given amount of work
Work (thermodynamics)
In thermodynamics, work performed by a system is the energy transferred to another system that is measured by the external generalized mechanical constraints on the system. As such, thermodynamic work is a generalization of the concept of mechanical work in mechanics. Thermodynamic work encompasses...
would generate the same amount of heat, provided the work done is totally converted to heat energy.
History and priority dispute
Benjamin Thompson
Sir Benjamin Thompson, Count Rumford , FRS was an American-born British physicist and inventor whose challenges to established physical theory were part of the 19th century revolution in thermodynamics. He also served as a Lieutenant-Colonel in the Loyalist forces in America during the American...
had observed the frictional heat generated by boring cannon at the arsenal in Munich, Germany circa 1797. Rumford immersed a cannon barrel in water and arranged for a specially blunted boring tool. He showed that the water could be boiled within roughly two and a half hours and that the supply of frictional heat was seemingly inexhaustible. Based on his experiments, he published "An Experimental Enquiry Concerning the Source of the Heat which is Excited by Friction", (1798), Philosophical Transaction of the Royal Society p.102. This was the scientific paper by Benjamin Thompson
Benjamin Thompson
Sir Benjamin Thompson, Count Rumford , FRS was an American-born British physicist and inventor whose challenges to established physical theory were part of the 19th century revolution in thermodynamics. He also served as a Lieutenant-Colonel in the Loyalist forces in America during the American...
, Count Rumford, that provided a substantial challenge to established theories of heat and began the 19th century revolution in thermodynamics. The experiment inspired the work of James Prescott Joule
James Prescott Joule
James Prescott Joule FRS was an English physicist and brewer, born in Salford, Lancashire. Joule studied the nature of heat, and discovered its relationship to mechanical work . This led to the theory of conservation of energy, which led to the development of the first law of thermodynamics. The...
in the 1840s. Joule's more exact measurements on equivalence were pivotal in establishing the kinetic theory at the expense of the caloric theory. The idea that heat and work are equivalent was also proposed by Julius Robert von Mayer in 1842 in the leading German physics journal and independently by James Prescott Joule in 1843 in the leading British physics journal. Similar work was carried out by Ludwig A. Colding
Ludwig A. Colding
Ludwig August Colding was a Danish civil engineer and physicist who articulated the principle of conservation of energy contemporaneouly with, and independently of, James Prescott Joule and Julius Robert von Mayer though his contribution was largely overlooked and neglected.-Life:Born in Holbæk,...
in 1840-1843, though Colding's work was little known outside his native Denmark. A collaboration between Nicolas Clément and Sadi Carnot
Sadi Carnot
Sadi Carnot may refer to:*Nicolas Léonard Sadi Carnot , French physicist*Marie François Sadi Carnot , president of the third French Republic, and nephew of Nicolas Léonard Sadi Carnot...
in the 1820s had some related thinking near the same lines. In 1845 Joule published a paper entitled "The Mechanical Equivalent of Heat", in which he specified a numerical value for the amount of mechanical work required to produce a unit of heat. In particular Joule had experimented on the amount of mechanical work generated by friction needed to raise the temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
of a pound
Pound (mass)
The pound or pound-mass is a unit of mass used in the Imperial, United States customary and other systems of measurement...
of water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
by one degree Fahrenheit
Fahrenheit
Fahrenheit is the temperature scale proposed in 1724 by, and named after, the German physicist Daniel Gabriel Fahrenheit . Within this scale, the freezing of water into ice is defined at 32 degrees, while the boiling point of water is defined to be 212 degrees...
and found a consistent value of 772.24 foot pound force (4.1550 J
Joule
The joule ; symbol J) is a derived unit of energy or work in the International System of Units. It is equal to the energy expended in applying a force of one newton through a distance of one metre , or in passing an electric current of one ampere through a resistance of one ohm for one second...
·cal
Calorie
The calorie is a pre-SI metric unit of energy. It was first defined by Nicolas Clément in 1824 as a unit of heat, entering French and English dictionaries between 1841 and 1867. In most fields its use is archaic, having been replaced by the SI unit of energy, the joule...
-1). Joule contended that motion
Motion (physics)
In physics, motion is a change in position of an object with respect to time. Change in action is the result of an unbalanced force. Motion is typically described in terms of velocity, acceleration, displacement and time . An object's velocity cannot change unless it is acted upon by a force, as...
and heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
were mutually interchangeable and that, in every case, a given amount of work
Work (thermodynamics)
In thermodynamics, work performed by a system is the energy transferred to another system that is measured by the external generalized mechanical constraints on the system. As such, thermodynamic work is a generalization of the concept of mechanical work in mechanics. Thermodynamic work encompasses...
would generate the same amount of heat. Von Mayer also published a numerical value for mechanical equivalent of heat in 1845 but his experimental method wasn't as convincing.
Though a standardised value of 4.1860 J·cal-1 was established in the early 20th century, in the 1920s, it was ultimately realised that the constant is simply the specific heat of water, a quantity that varies with temperature between the values of 4.17 and 4.22 J·g
Gram
The gram is a metric system unit of mass....
-1·°C
Celsius
Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
-1. The change in unit was the result of the demise of the calorie as a unit in physics and chemistry.
Both von Mayer and Joule met with initial neglect and resistance, despite having published in leading European physics journals. But by 1847 lots of the leading scientists of day were paying attention. Hermann Helmholtz in 1847 published what is considered a definitive declaration of the conservation of energy
Conservation of energy
The nineteenth century law of conservation of energy is a law of physics. It states that the total amount of energy in an isolated system remains constant over time. The total energy is said to be conserved over time...
. Helmholtz had learned from reading Joule's publications, though Helmholtz eventually came around to crediting both Joule and von Mayer for priority.
Also in 1847, Joule made a well-attended presentation at the annual meeting of British Association for the Advancement of Science
British Association for the Advancement of Science
frame|right|"The BA" logoThe British Association for the Advancement of Science or the British Science Association, formerly known as the BA, is a learned society with the object of promoting science, directing general attention to scientific matters, and facilitating interaction between...
. Among those in attendance was William Thomson
William Thomson, 1st Baron Kelvin
William Thomson, 1st Baron Kelvin OM, GCVO, PC, PRS, PRSE, was a mathematical physicist and engineer. At the University of Glasgow he did important work in the mathematical analysis of electricity and formulation of the first and second laws of thermodynamics, and did much to unify the emerging...
. Thomson was intrigued but initially skeptical. Over the next two years, Thomson became increasingly convinced of Joule's theory, finally admitting his conviction in print in 1851, simultaneously crediting von Mayer. Thomson collaborated with Joule, mainly by correspondence, Joule conducting experiments, Thomson analysing the results and suggesting further experiments. The collaboration lasted from 1852 to 1856. Its published results did much to bring about general acceptance of Joule's work and the kinetic theory
Kinetic theory
The kinetic theory of gases describes a gas as a large number of small particles , all of which are in constant, random motion. The rapidly moving particles constantly collide with each other and with the walls of the container...
.
However, in 1848, von Mayer had first had sight of Joule's papers and wrote to the French
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
Académie des Sciences to assert priority. His letter was published in the Comptes Rendus
Comptes rendus
Comptes rendus de l'Académie des Sciences, or simply Comptes rendus, is a French scientific journal which has been published since 1666. It is the proceedings of the French Academy of Sciences...
and Joule was quick to react. Thomson's close relationship with Joule allowed him to become dragged into the controversy. The pair planned that Joule would admit von Mayer's priority for the idea of the mechanical equivalent but to claim that experimental verification rested with Joule. Thomson's associates, co-workers and relatives such as William John Macquorn Rankine
William John Macquorn Rankine
William John Macquorn Rankine was a Scottish civil engineer, physicist and mathematician. He was a founding contributor, with Rudolf Clausius and William Thomson , to the science of thermodynamics....
, James Thomson
James Thomson
James Thomson may refer to:-Politicians:* James Thomson , 19th century political figure* James William Thomson , New Zealand politician...
, James Clerk Maxwell
James Clerk Maxwell
James Clerk Maxwell of Glenlair was a Scottish physicist and mathematician. His most prominent achievement was formulating classical electromagnetic theory. This united all previously unrelated observations, experiments and equations of electricity, magnetism and optics into a consistent theory...
, and Peter Guthrie Tait
Peter Guthrie Tait
Peter Guthrie Tait FRSE was a Scottish mathematical physicist, best known for the seminal energy physics textbook Treatise on Natural Philosophy, which he co-wrote with Kelvin, and his early investigations into knot theory, which contributed to the eventual formation of topology as a mathematical...
joined to champion Joule's cause.
However, in 1862, John Tyndall
John Tyndall
John Tyndall FRS was a prominent Irish 19th century physicist. His initial scientific fame arose in the 1850s from his study of diamagnetism. Later he studied thermal radiation, and produced a number of discoveries about processes in the atmosphere...
, in one of his many excursions into popular science
Popular science
Popular science, sometimes called literature of science, is interpretation of science intended for a general audience. While science journalism focuses on recent scientific developments, popular science is broad-ranging, often written by scientists as well as journalists, and is presented in many...
and many public disputes with Thomson and his circle, gave a lecture at the Royal Institution
Royal Institution
The Royal Institution of Great Britain is an organization devoted to scientific education and research, based in London.-Overview:...
entitled On Force in which he credited von Mayer with conceiving and measuring the mechanical equivalent of heat. Thomson and Tait were angered, and an undignified public exchange of correspondence took place in the pages of the Philosophical Magazine
Philosophical Magazine
The Philosophical Magazine is one of the oldest scientific journals published in English. Initiated by Alexander Tilloch in 1798, in 1822 Richard Taylor became joint editor and it has been published continuously by Taylor & Francis ever since; it was the journal of choice for such luminaries as...
, and the rather more popular Good Words. Tait even resorted to championing Colding's
Ludwig A. Colding
Ludwig August Colding was a Danish civil engineer and physicist who articulated the principle of conservation of energy contemporaneouly with, and independently of, James Prescott Joule and Julius Robert von Mayer though his contribution was largely overlooked and neglected.-Life:Born in Holbæk,...
cause in an attempt to undermine von Mayer.
Though Tyndall again pressed von Mayer's cause in Heat: A Mode of Motion (1863) with the publication of Sir Henry Enfield Roscoe
Henry Enfield Roscoe
Sir Henry Enfield Roscoe, FRS was an English chemist. He is particularly noted for early work on vanadium and for photochemical studies.- Life and work :...
's Edinburgh Review
Edinburgh Review
The Edinburgh Review, founded in 1802, was one of the most influential British magazines of the 19th century. It ceased publication in 1929. The magazine took its Latin motto judex damnatur ubi nocens absolvitur from Publilius Syrus.In 1984, the Scottish cultural magazine New Edinburgh Review,...
article Thermo-Dynamics in January 1864, Joule's reputation was sealed while that of von Mayer entered a period of obscurity.
Further reading
- Foucault, L.Léon FoucaultJean Bernard Léon Foucault was a French physicist best known for the invention of the Foucault pendulum, a device demonstrating the effect of the Earth's rotation...
(1854) “Equivalent mécanique de la chaleur. M. Mayer, M. Joule. Chaleur spécifique des gaz sous volume constant. M. Victor Regnault”, Journal des débats politiques et littéraires, Thursday 8 June, pp154-5 - Smith, C. (2004) "Joule, James Prescott (1818-1889)", Oxford Dictionary of National Biography, Oxford University Press,
- Zemansky, M.W. (1968) Heat and Thermodynamics: An Intermediate Textbook, McGraw-Hill, pp86-87