joule apparatus experiment

Before we begin our experiment, a little bit about the physical units involved. The following explanation refers to the more modern and popular SI system of units that can be converted with no much effort (also with the help of online converters) to English units if needed.

The small calorie or gram calorie (symbol: cal) is the energy needed to increase the temperature of 1 gram of water by 1 °C. This is about 4.2 joules.

The large calorie , kilogram calorie or food calorie (symbol: Cal) is the energy needed to increase the temperature of 1 kilogram of water by 1 °C. This is exactly 1000 small calories or about 4.2 kilojoules (4200 J).

In an attempt to avoid confusion, the large calorie is sometimes written as Calorie (with a capital C). This convention, however, is not always followed. Whether the large or small calorie is intended often must be inferred from context. When used in scientific contexts, the term calorie refers to the gram calorie (small calorie). In nutritional contexts, however, a larger unit is more useful. In such contexts the term calorie can be taken to refer to the kilogram calorie (symbol: kcal).

1 Joule is the energy consumed in applying a force of one newton through a distance of one metre (1 newton•metre or N•m).

Specific heat of water = the energy needed to increase the temperature of 1g of water by 1° C (by definition of the calorie) = 1 cal or 4.18 J (inferred from the mechanical equivalent of heat value). Take in account that other materials and liquids have different values for their specific heat.

Joule made a series of measurements and found that, on average a weight of 772 pounds falling through a distance of one foot would raise the temperature of one pound of water by 1° F. 772 pounds means around 350 kg – not so practical of a weight to experiment with. Therefore, Joule used a lesser weight falling over a greater distance, repeated a number of times.

In order to increase the temperature of 1kg (1 liter) of water by 1° C you’ll need some 4200 J of energy generated by the falling body. According to the potential energy loss of the falling body 4200=m*g*h where g the gravitational constant is around 10 m/s 2 so our equation comes to 4200=10m*h or 420=m*h . If we are going to use a mass of 1kg and drop it from a height of 1 m, then we’ll need to repeat this procedure 420 times in order to conclude the experiment.

From this simple equation ( 420=m*h ) is clear that increasing the mass m or the height h or using a sensitive thermometer say with digital display of 0.1°C, with no big effort we can reduce the repetitions needed to much less than one hundred.

We should take in consideration that some energy will be lost by the friction of the falling weight with the air, the string / rope friction, and heat transferred to the insulated barrel. So, your results will be a little higher than the 4.18 J/c. Therefore, the barrel must be caped and insulated as much as possible and the thermometer inserted through the cape not allowing contact with room air. And the experiment should be performed around 25 °C room temperature since physical values are defined for room temperature.

In order to achieve accurate results as much as possible it is recommended to repeat the entire experiment a few times, remove the extremes and calculate the average.

Another option for experimentation with Joule's apparatus is to try to measure the specific heat of other liquids than water.

December 1840: Joule’s Abstract on Converting Mechanical Power Into Heat

Scientists in the early 19th century adhered to caloric theory, first proposed by Antoine Lavoisier in 1783 and further bolstered by the work of Sadi Carnot in 1824. The work of a brewer and amateur scientist on the nature of heat and its relationship to mechanical work would give rise to the first law of thermodynamics.

Born in 1818, James Prescott Joule came from a long line of brewers, so chemistry was in his blood –as was scientific experimentation. Described as “delicate” in contemporary accounts, he and his brother experimented with electricity by giving each other electric shocks, as well as experimenting on the servants. The two boys were tutored at home until 1834, when their father sent them to study under John Dalton, one of the leading chemists of that time, at the Manchester Literary and Philosophical Society. Two years later, Dalton suffered a stroke and was forced to retire from teaching. The Joule brothers’ education was entrusted to John Davies.

Eventually Joule took over as manager of the family brewery, but science remained an active hobby. Fascinated by the emerging field of thermodynamics, Joule jerry-rigged his own equipment at home–using salvaged materials–to conduct scientific experiments–initially to test the feasibility of replacing the brewery’s steam engines with the newfangled electric motor that had just been invented. He found that burning a pound of coal in a steam engine produced five times as much work (then known as “duty”) as a pound of zinc consumed in an early electric battery. His brewery was better off with the steam engines. His standard of “economical duty” was the ability to raise one pound by one foot (the “foot-pound”).

His first experiments focused on electromagnetism and he quickly showed a gift for experimental apparatus; he built his first electromagnetic engine at 19, as well as improved galvanometers for measuring electrical current. Thanks to Dalton’s influence, Joule was a rare subscriber to atomic theory, and sought to explain electricity and magnetism in terms of atoms wrapped by a "calorific ether in a state of vibration."

This did not match his experimental results, however, and in December 1840, Joule published a short abstract in the Proceedings of the Royal Society suggesting that the heat generated in a wire conveying an electrical current results from the heat generated by the chemical reactions in a voltaic cell. In other words, heat is generated, not merely transferred from some other source in an electromagnetic engine. Based on this work, he formulated “Joule’s Law,” which states that the heat produced in a wire by an electric current is proportional to the product of the resistance of the wire and the square of the current.

When Joule presented these findings in a paper read before the British Association meeting in Cambridge, he concluded, “[T]he mechanical power exerted in turning a magneto-electric machine is converted into the heat evolved by the passage of the currents of induction through its coils; and, on the other hand, that the motive power of the electro-magnetic engine is obtained at the expense of the heat due to the chemical reactions of the battery by which it is worked.”

In subsequent papers presented in 1841 and 1842, he quantified this heating effect, demonstrating that the total amount of heat produced in a circuit during “voltaic action” was proportional to the chemical reactions taking place inside the voltaic pile. By January 1843, he had concluded that his magneto-electric machine enabled him to convert mechanical power into heat. All of this led Joule to ultimately reject the caloric theory of heat. He also established that the various forms of energy are basically the same and can be changed from one into another, a discovery that formed the basis of the law of conservation of energy, the first law of thermodynamics.

In his most famous experiment. Joule attached some weights to strings and pulleys and connected them to a paddle wheel inside an insulated container of water. Then he raised the weights to an appropriate height and slowly dropped them. As they fell, the paddle wheel began to turn, stirring up the water. This friction generated heat, and the temperature of the water began to increase.

It was the very precision of his measurements that caused some scientists to balk at accepting Joule’s findings. He claimed to be able to measure temperatures to within 1/200 of a degree Fahrenheit, which would have been astonishing to a 19th century scientist. Some historians have speculated that Joule’s experience in the art of brewing may have given him skills with experimental apparatus that his colleagues lacked. He also worked with John Benjamin Dancer, England’s finest instrument maker, to build highly accurate thermometers. Among those inclined to accept Joule’s work were Michael Faraday and William Thomson (Lord Kelvin), although they remained skeptical.

Thomson and Joule eventually became good friends and scientific collaborators. Thomson recalled in his memoir meeting Joule and his new wife, Amelia, during a tour of Mont Blanc in 1847. Joule was carrying a thermometer and claimed he would attempt to measure the thermal effects of fluid motion in local waterfalls. Thomson joined him a few days later at the Cascade de Sallanches, but they “found it much too broken into spray” to make a useful measurement. For several years, Joule conducted experiments and sent his results in letters to Thomson, who analyzed them from a theoretical standpoint and suggested further experiments Joule might try. Among the fruits of this partnership was the Joule-Thomson effect, in which an expanding gas, under certain conditions, is cooled by the expansion.

Joule lost his wife and daughter in 1854, and lived a fairly secluded life from then on. He died on October 11, 1889, and his gravestone is inscribed with the number 772.55–his most accurate 1878 measurement of the mechanical equivalent of heat. His work did not go unrecognized: the Queen of England granted him a pension in 1878 in recognition of his scientific achievements. The value of the mechanical equivalent of heat is represented by the letter J in his honor, and the standard unit of work is the joule.

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LEXPERIMENTAL PHYSICS

Mechanical Equivalent of Heat

Joule experiment, the original joule experiment consists of a receptacle filled with water and a mechanism with spinning plates. the kinetic energy of the plates is transformed into heat, because the force of gravity performs work on the weight falling a distance . this gave an experimental confirmation of the equivalence between heat and work, now defined to be exactly 1 calorie for every 4.1855 joules and called a "thermochemical calorie"., set the mass of the two suspended spheres in kg, set the mass of water contained in the calorimeter (includes the equivalent mass in water of the calorimeter) in grams, enter a value by moving  the sliders or by entering the numbers in the corresponding boxes, press the "start" button, suspended objects will be free to fall under the action of gravity;, at the end of the  fall the thermometer will mark a given temperature, greater than the initial one;, press the "start" button to drop the masses again ;, press the "reset" button to reset all the initial conditions;, proposed activity, press the reset button, record the initial temperature ti, drop the spheres n times, record the final temperature tf, calculate the work done: l = 2mgh * n ( we have 2 falling masses and the  height h = 2m), calculate the product heat : q =ma (tf-ti) * c (c: specific heat of water = 1cal / (g ° c),       ma = mass of water + equivalent mass in water of the calorimeter), calculate  j = l / q, note mass of spheres  in kilograms water mass in grams sensitivity of the thermometer 0.1 c length of the fall 2m ±1cm, james prescott joule (1818 – 1889) calculated in 1843 the mechanical equivalent of heat in a series of experiments. in the most famous apparatus he built for this end, now called the joule apparatus (see image below), a descending weight attached to a string caused a paddle immersed in water to rotate and heat the water. joule supposed that the gravitational potential energy lost by the weight in descending was equal to the thermal energy (heat) gained by the water by friction with the paddle., in this experiment, the friction and agitation by the paddle-wheel of the body of water, trapped in an insulated barrel (calorimeter), caused heat to be generated which, in turn, increased the temperature of the water. the temperature change ∆t of the water and the height of the fall ∆h of the weight m*g were recorded. using these values, joule was able to determine the mechanical equivalent of heat., joule contended that motion and heat were mutually interchangeable and that, in every case, a given amount of work (motion) would generate the same amount of heat. moreover, he also claimed that heat was only one of many forms of energy (electrical, mechanical, chemical) and only the sum of all forms was conserved. otherwise the calculated mechanical equivalent of heat is meaningless., in 1845, james joule reported his experiment in a paper on the mechanical equivalent of heat for the british association meeting in cambridge..

The quantity of heat produced is given by Q = C (Tf - Ti) cal, in which (Tf - Ti) is the difference between the final and initial temperature and C it is the total amount of heat of the system, given from Ma*ca +Mr*cr, in which Ma, ca and Mr, cr are respectively the masses and the specific heats of the distilled water and the calorimeter.

Problems/exercises, ( please insert here some problems and/or exercises), torna alla pagina principale.

Joule and the Conservation of Energy

James Joule was born in 1818, the second son of a prosperous brewer in Manchester, England. His father hired John Dalton (who had proposed the atomic theory of chemistry in 1803) as a private tutor for his two sons.   Dalton met with the boys twice a week, guided them through Euclid’s books on geometry, and covered a vast range of natural phenomena.   There was also a wilder side to Joule’s science education: he blew his eyebrows off in a gun experiment; he flew kites in thunderstorms. He asked a servant girl to report her sensations as he gave her increasing electric shocks, but stopped when she fell unconscious. (Cardwell, page 16).

But Joule worked with meticulous care in the laboratory. In 1840, at the age of 22, he established that a conductor carrying an electric current became hot, and that the rate of heating for a current I flowing through a resistance R was given by I 2 R for any kind of wire , and even for electric currents in fluids.   This was a kind of heat production no-one had seen before—previously, heat had only come from either chemical combustion, or friction, or radiation. And, sad to relate, Rumford’s assertions had had little impact on the scientific community, so the big question was: how did the electric current deliver caloric fluid into the wire?    Well, actually, this wasn’t too difficult to explain.   In the battery, caloric was no doubt being released in the chemical reactions involved in producing the electric current, and the caloric was then transported down the wire by the current.  

( Cultural footnote : Cardwell, page 35)   F rom a London perspective, Manchester was (and maybe still is) the boondocks.   When Joule submitted his paper on the discovery of the electrical I 2 R heating (now known as Joule heating) to the Royal Society, it was rejected, except for a short abstract.   Much later, when asked if that cursory treatment surprised him, he replied : “I was not surprised—I could imagine those gentleman in London sitting round a table and saying to each other ‘what good can come out of a town where they dine in the middle of the day?’”

Next, Joule did an experiment that was tougher for the caloric theory to explain.   He found that the very same heating of the wire took place if the electrical current involved, instead of being generated by chemical reactions in a battery, came from a dynamo, a simple coil of wire rotating in a magnetic field.   Now where was the “caloric fluid” coming from?   The only explanation anyone could come up with was that rotating the coil in the magnetic field must be somehow pumping caloric out of it.   So the coil should cool down.   Joule tested this hypothesis, and found that instead the coil heated up a little. It was impossible to reconcile this finding with the caloric theory—heat could not be a conserved fluid after all. Joule wrote that in magneto electricity, we have an agent capable by simple means of … generating heat .   (Cardwell, page 56).

So “caloric fluid” could be manufactured!   The basic assumption of the caloric theory, that this was a conserved fluid, was wrong!   Joule next asked if a given amount of work always produced the same amount of heat (we’ll say “heat” instead of the discredited “caloric fluid” from now on). He drove his electrical generator at a steady pace by wrapping fine string around the axle, and tying a weight to the end of it.   As the weight fell, the generator settled to a steady pace, which he timed. He then turned the generator at that pace by hand for fifteen minutes, and measured how much heat was generated in a piece of wire immersed in a calorimeter.   From that measurement, he was able to calculate that the amount of heat required to raise the temperature of one pound of water by 1 ° F (that is, one British Thermal Unit of heat, usually written one BTU) could be generated by an 896 pound weight falling through one foot—or a one pound weight falling through 896 feet, etc., in other words, 896 foot × pounds of mechanical work.   This figure is in the right ballpark, but almost 20% too high—his later, much more accurate, measurement was 772 foot × pounds per BTU. This was the first time anyone had stated that a measured quantity of heat was equivalent to a corresponding amount of mechanical work .

Finally, in 1845, Joule realized that the electrical apparatus was an unnecessary intermediary—heat could be produced directly by a falling weight.   He arranged for the falling weight to drive paddle wheels in a calorimeter, churning up the water.   This led to a slight but measurable rise in temperature. He found one BTU was generated by an energy expenditure of 772 foot × pounds (switching his results to the metric system, that one calorie was the equivalent of 4.2 newton.meters, or, as we now say, 4.2 joules).   Incidentally, Joule amused himself by demonstrating that Rumford’s detailed records of bringing the water to a boil in the cannon boring could be used to find the mechanical equivalent of heat.   Rumford had claimed that he had two horses working for two and a half hours, but he was working them lightly, they were only really doing the work of one.   Joule used Watt’s estimate that one horse can work at 33,000 foot × pounds per minute to find an equivalence of over 1000 foot × pounds per BTU, about fifty percent too high, but not a bad estimate in view of all the uncertainties involved.  

Joule also calculated that the water just beyond the bottom of a waterfall will be one degree Fahrenheit warmer than the water at the top for every 800 feet of drop, approximately, the kinetic energy turning to heat as the water crashed into rocks at the bottom.   Joule spent his honeymoon at Chamonix in the French Alps, and Lord Kelvin claimed later that when he chanced to meet the honeymooners in Switzerland, Joule was armed with a large thermometer to check out the local waterfalls (but it is generally believed that Kelvin made this up).

Joule also did a series of beautiful experiments on electrolysis and combustion. Batteries work because some of the ions in solution are chemically attracted to the metal plates. For example, oxygen ions move to a zinc or iron plate, become chemically attached and deliver charge.   By carefully measuring currents, Joule was able to find the “affinity” of oxygen with plates of various elements.   He then compared this with the heat produced when zinc or iron, say, were burned in an oxygen atmosphere. He saw, correctly, that this was just another way for oxygen to attach itself to these metals, and he was able to confirm that the same heat was released in these very different-seeming reactions.   These chemical investigations, carried out in 1842, were no doubt in the back of his mind when he found that heat was interchangeable with mechanical and electrical energy, and suggested that chemical energy, too, must be in the list.

Joule’s work was so impressive that his provincial origins were forgiven, and by the late 1840’s he was regularly presenting papers to the British Association and the Royal Society.   His experiments establishing the equivalence of heat and mechanical work, the cornerstone of the principle of conservation of energy, are among the greatest achievements of nineteenth-century science.

But was Carnot so wrong?

On the face of it, once it became clear that the caloric fluid wasn’t conserved, and therefore didn’t exist in the way Carnot and others had imagined, one would think that Carnot’s elegant analysis of the heat engine as a water wheel using caloric fluid had little remaining value.   But that turned out not to be the case.   In particular, his analysis of the efficiency of a heat engine was right.

James Joule: A Biography , Donald S. L. Cardwell, Manchester University Press.

The National MagLab is funded by the National Science Foundation and the State of Florida.

James Joule

James Prescott Joule experimented with engines, electricity and heat throughout his life.

Joule’s findings resulted in his development of the mechanical theory of heat and Joule’s law , which quantitatively describes the rate at which heat energy is produced from electric energy by the resistance in a circuit. Initially many 19th century scientists were skeptical of Joule’s work, but his efforts proved fundamental to the modern understanding of thermodynamics. The SI unit of work, the joule , was named in honor of his significant scientific contributions.

A native of England, Joule was born on December 24, 1818, in Salford, Lancashire. His family was quite wealthy due to the success of the family brewery business. As a teenager, Joule began studying with the renowned chemist John Dalton at the University of Manchester, but a sudden change for the worse in Dalton’s health prematurely ended the tutelage. Despite their short time together, Dalton’s emphasis on quantitative experiments had a lasting effect on Joule’s scientific techniques. Joule continued his education under the guidance of John Davis, who co-founded the Royal Victoria Gallery for the Encouragement and Illustration of Practical Science.

Joule’s earliest interests in science concerned electromagnetic engines and their strength and weaknesses as compared to steam engines. His involvement with the family brewery helped direct his attention to this area because more efficient engines could substantially improve the profitability of the business. Joule’s first published paper was “Description of an electro-magnetic engine” , which appeared in 1838 in Annals of Electricity . Displeased by his discovery that steam engines appeared to be much better at work production than the electromagnetic engines available at the time, he embarked on an experimental journey in which he tried to improve the performance of the electromagnetic engine by varying the arrangement of iron in the device.

Joule’s dedication to experimentation eventually led to his formulation of the law that now bears his name in 1840. According to Joule’s law, the heat generated in an electric wire is proportional to the current squared multiplied by the resistance. The law is often written as P=I 2 R , where P equals power loss, I is the current in amperes, and R is the resistance given in ohms. Joule included the law within the treatise “On the Production of Heat by Voltaic Electricity” , which was published in abbreviated form in the Proceedings of the Royal Society . However, the youth of its author and the perception of others that he was merely a hobbyist prevented many members of the Society from immediately realizing the importance of Joule’s work.

The cool reception he received did not deter Joule, who forged ahead with additional experiments involving electricity and heat. Soon after, he began giving lectures at the Royal Victoria Gallery, and by 1843 began publicly speculating on the convertibility of energy. That same year he published his early calculations on the amount of work needed to generate a unit of heat that he termed the mechanical equivalent of heat . Over the course of his career, Joule continually improved his methods of determining the mechanical equivalent of heat and repeatedly refined the value of the unit. His final calculation for the unit was about 772 foot pound force, that is, according to Joule, the heat required to raise the temperature of one pound of water a single degree Fahrenheit was equivalent to (and convertible into) a mechanical force that could lift approximately 772 pounds one foot high.

In the late 1840s, Joule wed Amelia Grimes. Not long after, Joule’s contemporaries became somewhat more receptive of his work, largely due to his acquaintance and collaboration with William Thomson , later better known as Lord Kelvin. Thomson, who had witnessed one of Joule’s lectures to the British Association for the Advancement of Science, was very interested in his thermodynamic experiments. Yet he was also concerned with their apparent conflict with the then widely accepted caloric theory originally proposed by Antoine Lavoisier, which stated that heat existed as a type of fluid that flowed from warmer to cooler bodies. Correspondence between Joule and Thomson over the course of many years, as well as additional experiments (some suggested by Thomson) and refinements in technique, eventually led Thomson to support fully Joule’s mechanical theory of heat. Their association with one another also resulted in the discovery of the Joule-Thomson effect , a phenomenon in which a gas allowed to expand freely experiences a change in temperature. The Joule-Thomson effect laid the foundation for the emergence of the refrigeration business.

During the latter part of his career, Joule received much of the attention and accolades withheld from him in his earlier years. In 1850, following his publication of one of his most consistent calculations of the mechanical equivalent of heat, Joule became a fellow of the Royal Society, from which he received the Royal Medal in 1852 and the Copley Medal in 1870. Various institutions of higher learning, including Trinity College Dublin, University of Oxford and University of Edinburgh, also awarded him with honorary degrees, and the Royal Society of Arts bestowed to him the Albert Medal (1880).

Nevertheless, some controversy surrounded the priority of Joule’s thermodynamic work. A German physicist, Julius Robert von Mayer, claimed that he proposed the equivalency of heat and work at least a year before Joule announced his mechanical theory of heat. In order to help resolve the issue with as little enmity as possible, Joule eventually conceded Mayer’s claim for earlier development of the theory while asserting his own priority in experimentally confirming the theory. Despite the concession, however, most publications have since given primary recognition to Joule, who passed away at his home on October 11, 1889.

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Provides one of Joule’s most important experiments, converting mechanical work to thermal energy.

See the Product Description for this item's included accessories.

See the Buying Guide for this item's required, recommended, and additional accessories.

Product Summary

• Crank Counter: Counts the number of turns on the handle.
• Thermistor: Embedded in the cylinder, it has lower thermal mass
• Durable Construction: Constructed primarily of steel and aluminum, there’s virtually nothing to break. The thermistor is protected in the cylinder.

How It Works

Turn the crank to perform a measurable amount of work. The crank turns an aluminum cylinder. A flat nylon rope is wrapped several times around the cylinder. As the crank is turned, the friction between the rope and the cylinder is just enough to support a mass hanging from the other end of the rope. This ensures that the torque acting on the cylinder is constant and measurable. A counter keeps track of the number of turns of the crank. The thermal energy is measured by monitoring the temperature of the cylinder using the embedded thermistor.

With this apparatus, the equivalence of work and heat is easily established to within 5%.

What's Included

• 1x Base, cylinder, crank, and counter with a built-in table clamp
• 1x 1-gallon can that can be filled with a measured mass of sand or water (if 10 kg of laboratory masses are not available)
• 1x 3.7 m of flat nylon rope
• 1x Laboratory manual including theory, step-by-step instructions, and data tables

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