For example, since it tended to flow from hot bodies into cold bodies and spread throughout the body, presumably its particles repelled each other, just like those of the electrical fluid. However, in contrast to electricity, which had no noticeable effect on the appearance of a charged object, when heat was added to a solid things changed considerably.
First the material expanded, then it changed to a liquid and finally to a gas, if sufficient heat could be delivered. Further heating expanded the gas, or increased its pressure if it was held in a fixed container. To interpret this sequence of events in terms of a caloric fluid being fed into the material, one could imagine the fluid flowing between the atoms of the solid and lessening their attraction for each other, until the solid melted into a liquid, whereupon the caloric continued to accumulate around the atoms until they were pushed apart into a gas.
It was thought that in the gas each atom or molecule was surrounded by a ball of caloric, like a springy ball of wool, and these balls were packed in a container like oranges in a crate, except that the caloric balls could expand indefinitely as heat was poured in. Various other effects could be explained by the caloric theory: when a gas is suddenly compressed, it gets hotter because the same amount of caloric is now occupying a smaller volume.
When two solids are rubbed together, some caloric is squeezed out at the surfaces, or perhaps tiny pieces of material are rubbed off, and lose their caloric, so heat appears. Radiant heat was presumed to be caloric particles flying through space. Recall that at that time just before it was generally accepted that light was a stream of particles.
In a Lancashire wigmaker, Richard Arkwright , patented a successful cotton-spinning machine. Lancashire had been for a long time a center of the textile trade, but before Arkwright the fabrics were woven on hand looms by skilled weavers.
The new machines could be operated by less skilled workers, and in fact were largely operated by children, although, in contrast to some of his competitors, Arkwright refused to employ any child younger than six. The motive power driving the machines was at first horses, but in Arkwright built a large factory containing many machines all driven by a water wheel.
This was the beginning of the modern system of mass production. Prices fell, and the skilled hand weavers became impoverished.
Our interest in this, however, is not the social consequences, but just the water wheel. Previously, water wheels had been used for centuries to grind flour, and for other purposes, but their efficiency had not been a major concern. In the factory, though, the more efficient the wheel, the more children could be spinning the cotton, and the bigger the profits. Twenty years earlier, John Smeaton the first Englishman to call himself a civil engineer had investigated different types of water wheels, and found the overshot type in which the water pours on to the top of the wheel to perform best.
The ultimate in efficiency would be a reversible water wheel, which could be run backwards, to raise the water back again.
This is best visualized by having a wheel with a series of buckets attached. Suppose the wheel is run for some time and its power output is used to lift a weight a given distance. Now reverse it, let the weight fall, running the wheel backwards, making sure the buckets now fill at the bottom and empty at the top. How much water is lifted back up?
A truly reversible wheel would put all the water back. In building the first factory, the water wheel was not just placed under a waterfall. The water was channeled to it for maximum efficiency. Smeaton had established that the flow of water into the buckets must be as smooth as possible. The water should flow onto the wheel, not fall from some height. Finally, the perfect wheel not quite realizable in practice would be reversible—it could be run backwards to put the water back up using the same amount of work it delivered in the first place.
The next step was to use steam power, which had been developed in the previous century to lift water out of mines. As steam engine design improved, the English economy mushroomed far ahead of European competitors—but in contrast to the present day, these technological advances owed virtually nothing to basic science.
It was all inspired tinkering. The first attempt to analyze the steam engine in a scientific way was by a Frenchman, Sadi Carnot, in —and he relied heavily on an analogy with the water wheel. In the steam engine, heat is delivered to water to boil off steam which is directed through a pipe to a cylinder where it pushes a piston.
The piston does work, usually by turning a wheel, the steam cools down, and the relatively cold vapor is expelled, so that the piston will be ready for the next dose of steam.
Where is the analogy to a water wheel? Recall that heat was seen as an invisible fluid, impelled by its nature to flow from hot objects to cold objects. Water always flows from high places to low places. If we could make such a wheel with friction-free bearings, etc. Heat was fed into the gas, it expanded, then the heat supply was cut off, but the hot gas continued to expand and cool down at the same time.
The piston then reversed direction, and the heat generated by the compression was allowed to flow out into a heat sink, until a certain point was reached at which the sink was disconnected, and the further compression heated up the gas to its original temperature, at which point the cycle began again.
Carnot found, not surprisingly, that the amount of work a perfect engine could deliver for a given amount of heat increased as the temperature difference between heat source and heat sink increased. Obviously, water wheels get more energy from the same amount of water if the wheel is bigger so the water has further down to go. For a given temperature difference, then, a given amount of heat can only deliver so much work.
And, this is quite independent of the materials used in constructing the engine, including the gas itself. As we shall discuss in detail later, he was able to find for such an engine just how much work the engine could perform for a given heat input, and the answer was surprisingly low.
Furthermore, no engine could ever be more efficient than a reversible engine, because if it were, it could be used to drive the reversible engine backwards, replacing the heat in the furnace, with energy to spare, and would be a perpetual motion machine.
The first real attack on the caloric theory of heat took place in a cannon factory in Bavaria, under the direction of one Count Rumford of the Holy Roman Empire. This Count was actually born Benjamin Thompson in Woburn, in the English colony of Massachusetts, in , which he left in a hurry after choosing the wrong side in the Revolutionary War.
He was a brilliant man, extraordinarily inventive as a scientist and engineer—but it is difficult to form a coherent picture of his character. He seemed genuinely upset by the plight of the poor in Munich see below and made great personal efforts for years to ensure they were properly fed and clothed.
Throughout his life, he invented practical devices to make daily living better: stoves, fitted kitchens, drip coffeepots, lighting, and many more.
Yet, despite this love for humanity and his clear desire to make life better for everyone, Rumford did not apparently like—or get on with—actual people. The only exceptions were those with power who might prove useful, and almost any attractive woman he met. Rumford dumped his own family unceremoniously when war broke out and he fled to England. When garrisoned on Long Island in fighting for the British he treated the local people horribly.
He always engaged in shameless self-promotion, often with little regard for the truth. But he did make important contributions to many fields: food, clothing, work and education for the poor both in Bavaria and less successfully later in England, and all manner of engineering improvements, from the domestic devices listed above to state of the art artillery.
In fact, his artillery designs were so highly regarded that by US President Adams tried to persuade him to return to America to found a Military Academy, with assurances that all was forgiven. His father died when Benjamin was still a child, and although his mother remarried, he felt strongly that he had to take care of himself.
He worked hard at school, then at age eighteen began working as a tutor for children of rich families, and after a short time became a teacher in a school in Concord, New Hampshire.
At nineteen, he married a rich young widow, who decided to upgrade his appearance to fit in better with her friends. She bought him a scarlet hussar cloak, they used a two-horse chaise called a curricle, the only other curricle in the province belonging to the Royal Governor, John Wentworth. Thompson assiduously cultivated the Governor. They went together on a surveying expedition exploring the hilly country of the province. That year, the people were becoming increasingly rebellious against British rule and British taxes.
Order was kept, at least in part, by the British Army. The nature of heat was a matter of intense debate for centuries. On the one hand, there were supporters of the caloric theory of heat; often associated with the influential French chemist Antoine Laurent Lavoisier. On the other hand, there were Count Rumford and Humphry Davy who debunked the caloric theory.
Thermodynamics is literally the study of heat in motion or how heat moves. The heat theories and other ideas emerged gradually from many, many different researchers. It was in the early- and mid th century that the laws of thermodynamics were finally formulated and understood in a systematic way. Learn more about the nature of science.
Antoine Laurent Lavoisier lived from to He rose to a position of power and prestige in pre-revolutionary France. Despite being a lawyer, he soon turned to science as he was enthralled by chemistry and mineralogy.
Lavoisier was the champion of liberal social reform and he worked within the existing political system to try and implement those reforms. During the French Revolution, however, he was targeted as a sympathizer of the former regime. Subsequently, he was executed by guillotine on May 8, French mathematician Joseph-Louise Lagrange regretted the execution of Lavoisier.
The scientific work of Lavoisier was wide-ranging and he was a proponent of the heat theory called caloric theory. He performed meticulous chemical studies which involved careful documentation of both the products and the reactants of various chemical processes. This careful analysis of products and reactants was a rarity during his times.
Lavoisier was especially interested in the chemistry of burning and played a major role in the discovery of oxygen. He also contributed to the role of oxygen in combustion and oxidation reactions such as rusting. In this work, Lavoisier espoused his caloric theory, which described heat as a massless fluid, a fluid that could flow from one object to another.
Learn more about the ordered universe. There was disagreement from other scholars. These scholars saw heat as a manifestation of motion at the atomic scale and, thus, they thought of heat as a mechanical property of matter.
It was the opportunistic American-born inventor Benjamin Thompson Count Rumford who ultimately resolved the debate. And finally, when Sir Humphry Davy conducted experiments, the caloric theory was buried forever. This is a transcript from the video series The Joy of Science. Watch it now, on Wondrium. Count Rumford was always fascinated by the phenomenon of heat. He conducted numerous experiments and made inventions to improve the use of heat in everyday life.
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