P. Joule had assumed to be the same at all temperatures.
P. Joule found that magnetization did not increase proportionately with the current, but reached a maximum (Sturgeon's Annals of Electricity, 1839, 4).
P. Joule respectively, and the author of the first formal treatise on the subject.
P. Joule, who in 1842 and 1847 described some experiments which he had made upon bars of iron and steel.
As the result of their experiments on actual gases (air, hydrogen, and C02), Joule and Thomson (Phil.
Method of Joule and Thomson.
This inquiry yielded (in 1867) the result 783, and this Joule himself was inclined to regard as more accurate than his old determination by the frictional method; the latter, however, was repeated with every precaution, and again indicated 772.55 foot-pounds as the quantity of work that must be expended at sea-level in the latitude of Greenwich in order to raise the temperature of one pound of water, weighed in vacuo, from 60 to 61° F.
Joule inferred from them that the mechanical equivalent of heat is probably about 772 foot-pounds, or, employing the centigrade scale, about 1390 foot-pounds.
P. Joule, and particularly R.
Of greater interest, particularly from a historical point of view, are the original papers of Joule, Thomson and Rankine, some of which have been reprinted in a collected form.
Meters intended to measure electric energy (which is really the subject of the sale and purchase) are called joule meters, or generally watt-hour meters.
A more convenient unit of work or energy, in practice, on account of the smallness of the erg, is the joule, which is equal to 10.7 ergs, or one watt-second of electrical energy.
This most fundamental point was finally settled by a more delicate test, devised by Lord Kelvin, and carried out in conjunction with Joule (1854), which showed that the fundamental assumption W =H in isothermal expansion was very nearly true for permanent gases, and that F'(t) must therefore vary very nearly as J/T.
Assuming that the whole of the energy was converted into heat, when the air was subjected to a pressure of 21.5 atmospheres Joule obtained for the mechanical equivalent of heat about 824.8 foot-pounds, and when a pressure of only 10 .
Joule (1845) was the first to prove it approximately by direct experiment, but did not see his way to reconcile Carnot's principle, as stated by Clapeyron, with the mechanical theory.
On account of its practical convenience, and its close relation to the international electrical units, the joule has been recommended by the British Association for adoption as the absolute unit of heat.
Experiments by Natanson on CO 2 at 17° C. confirm those of Joule and Thomson, but show a slight increase of the ratio do/dp at higher pressures, which is otherwise rendered probable by the form of the isothermals as determined by Andrews and Amagat.
JAMES PRESCOTT JOULE (1818-1889), English physicist, was born on the 24th of December 1818, at Salford, near Manchester.
Electric magnets of great power were soon constructed in this manner by Sturgeon, Joule, Henry, Faraday and Brewster.
] Joule and others experimented with hardened steel, but failed to find a key to the results they obtained, which are rather complex, and have been thought to be inconsistent.
P. Joule, J.
Joule died at Sale on the 11th of October 1889.
joule impact (250g @ 20cm ).
Joule's experiments on the equivalence of W and H were not sufficiently precise to decide the question.
The earlier work of Joule is now chiefly of historical interest, but his later measurements in 1878, which were undertaken on a larger scale, adopting G.
P. Joule with the perforated piston and with the friction of water and mercury.
(If the molecules of air at normal temperature and pressure were arranged in cubical order, the edge of each cube would be about 2.9 X I o - ' cms.; the average diameter of a molecule in air is 2.8X Io - 8 cms.) Further and very important evidence as to the nature of the gaseous state of matter is provided by the experiments of Joule and Kelvin.
P. Joule, but the rise of temperature is then difficult to measure with accuracy, since it is necessarily reduced in nearly the same proportion as the correction.
(I.) The Method Corresponding To The Expression Cr T Was Adopted By Joule And By Most Of The Early Experimentalists.
The ideal method of determining by direct experiment the relation between the total heat and the specific heat of a vapour is that of Joule and Thomson, which is more commonly known in connexion with steam as the method of the throttling calorimeter.
Assuming dH/do = 0.305 for saturated steam, he found that S was nearly independent of the pressure at constant temperature, but that it varied with the temperature from o 387 at 100° C. to o 665 at 160° C. Writing Q for the Joule-Thomson " cooling effect," dO/dp, or the slope BC/AC of the line of constant total heat, he found that Q was nearly independent of the pressure at constant temperature, a result which agrees with that of Joule and Thomson for air and COs; but that it varied with the temperature as (1/0) 3.8 instead of (i/0) 2.
In this experiment a great noise was produced, corresponding to a loss of energy, and Joule endeavoured to determine the amount of energy necessary to produce an equal amount of sound from the string of a violoncello and to apply a corresponding correction.
Now, we know that the number of electrochemical equivalents electrolysed is proportional to the whole amount of electricity which passed through the circuit, and the product of this by the electromotive force of the battery is the work done by the latter, so that in this case also Joule showed that the heat generated was proportional to the work done.
In 1885 it was shown by Bidwell, in the first of a series of papers on the subject, that if the magnetizing force is pushed beyond the point at which Joule discontinued his experiments, the extension of the bar does not remain unchanged, but becomes gradually less and less, until the bar, after first returning to its original length, ultimately becomes actually shorter than when in the unmagnetized condition.
P. Joule after years of patient labour in direct experimenting.
P. Joule (Phil.
P. Joule and W.
P. Joule to achieve; his experiments conclusively prove that heat and energy are of the same nature, and that all other forms of energy can be transformed into an equivalent amount of heat.
The deviations from the ideal volume may also be deduced by the method of Joule and Thomson.
The best-known of Joule's experiments was that in which a brass paddle consisting of eight arms rotated in a cylindrical vessel of water containing four fixed vanes, which allowed the passage of the arms of the paddle but prevented the water from rotating as a whole.
It has been proposed to adopt the joule, with the symbol j, as thermochemical unit for small quantities of heat, large amounts being expressed in terms of the kilojoule, Kj =100o j.
Barrett in 1882 that a nickel bar contracts when magnetized, nothing of importance was added by Joule's results for nearly forty years.
According to Joule's observations, the length of a bar of iron or soft steel was increased by magnetization, the elongation being proportional up to a certain point to the square of the intensity of magnetization; but when the " saturation point " was approached the elongation was less than this law would require, and a stage was finally reached at which further increase of the magnetizing force produced little or no effect upon the length.
From data contained in Joule's paper it may be calculated that the strongest external field Ho produced by his coil was about 126 C.G.S.
The object of the present article is to illustrate the practical application of the two general principles - (I) Joule's law of the equivalence of heat and work, and (2) Carnot's principle, that the efficiency of a reversible engine depends only on the temperatures between which it works; these principles are commonly known as the first and second laws of thermodynamics.
Clausius (1850), applying the same assumption, deduced the same value of F'(t), and showed that it was consistent with the mechanical theory and Joule's experiments, but required that a vapour like steam should deviate more considerably from the gaseous laws than was at that time generally admitted.
- William Thomson (Lord Kelvin), who wars the first to realize the importance of the absolute scale in thermodynamics, and the inadequacy of the test afforded by Boyle's law or by experiments on the constancy of the specific heat of gases, devised a more delicate and practical test, which he carried out successfully in conjunction with Joule.
Joule's final result was 772.55 foot-bounds at Manchester per pound-degreeFahrenheit at a temperature of 62° F., but individual experiments differed by as much as I %.
measure is equivalent to 4.177 joules per calorie at 16.5° C., on the scale of Joule's mercury thermometer.
Employing Joule's value of the mechanical equivalent of heat, then recently published, in connexion with the value of the ratio of the specific heats of air S/s=I.
In this he used Joule's paddle-wheel method, though with many improvements, the whole apparatus being on a larger scale and the experiments being conducted over a wider range of temperature.
He obtained a result distinctly higher than Joule's final figure; and in addition he made many valuable observations on thermometrical questions and on the variation of the specific heat of water, which J.
An international committee was formed for the purpose of erecting a monument to his memory in Westminster Abbey; and there, in May 1895, a portrait medallion, by Albert Bruce Joy, was placed near the grave of Newton, and adjoining the memorials of Darwin and of Joule.
Peltier (1834) that heat is absorbed at the junction of two metals by passing a current through it in the same direction as the current produced by heating it, was recognized by Joule as affording a clue to the source of the energy of the current by the application of the principles of thermodynamics.
Unlike the frictional generation of heat due to the resistance of the conductor, which Joule (1841) Table I.-Thermoelectric Power, p=dE/dt, IN Microvolts At 50° C. Of Pure Metals With Respect To Lead.
of the couple, and if the flow of the current does not produce any other thermal effects in the circuit besides the Joule and Peltier effects, we should find by applying the principle of the conservation of energy, i.e.
by equating the balance of the heat absorbed by the Peltier effects to the heat generated in the circuit by the Joule effect, (P - P')C=CR=EC, whence E=P - P..
The Peltier effect was only a small fraction of the total effect, but could be separated from the Joule effect owing to the reversal of the current.
Ann., 1875), who regarded electricity as consisting of atoms much smaller than those of matter, and supposed that heat was the kinetic energy of these electric atoms. If we suppose that an electric current in a metal is a flow of negative electric atoms in one direction, the positive electricity associated with the far heavier material atoms remaining practically stationary, and if the atomic heat of electricity is of the same order as that of an equivalent quantity of hydrogen or any other element, the heat carried per ampere-second at o C., namely P, would be of the order of 030 of a joule, which would be ample to account for all the observed effects on the convection theory.
In 1847 Thomson first met James Prescott Joule at the Oxford meeting of the British Association.
Joule's views of the nature of heat strongly influenced Thomson's mind, with the result that in 1848 Thomson proposed his absolute scale of temperature, which is independent of the properties of any particular thermometric substance, and in 1851 he presented to the Royal Society of Edinburgh a paper on the dynamical theory of heat, which reconciled the work of N.
Mayer and Joule, and placed the dynamical theory of heat and the fundamental principle of the conservation of energy in a position to command universal acceptance.
butterfat content Joule A unit of energy.
joule Heating: Think of a herd of buffalo on the prairie.
joule in power.
joule of energy.
joule per coulomb.
Joule afterwards proved (see below) that Mayer's assumption was in accordance with fact, so that his method was a sound one as far as experiment was concerned; and it was only on account of the values of the specific heats of air at constant pressure and at constant volume employed by him being very inexact that the value of the mechanical equivalent of heat obtained by Mayer was very far from the truth.
Colding, who in 1843 presented to the Royal Society of Copenhagen a paper entitled "Theses concerning Force," which clearly stated the "principle of the perpetuity of energy," and who also performed a series of experiments for the purpose of determining the heat developed by the compression of various bodies, which entitle him to be mentioned among the founders of the modern theory of energy, we come to Dr James Prescott Joule of Manchester, to whom we are indebted more than to any other for the establishment of the principle of the conservation of energy on the broad basis on which it has since stood.
From these experiments Joule obtained 72.692 foot-pounds in the latitude of Manchester as equivalent to the amount of heat required to raise i lb of water through 1Ã‚° Fahr, from the freezing point.
Previous to determining the mechanical equivalent of heat by the most accurate experimental method at his command, Joule established a series of cases in which the production of one kind of energy was accompanied by a disappearance of some other form.
In 1844 and 1845 Joule published a series of researches on the compression and expansion of air.
But, unlike Mayer and Seguin, Joule was not content with assuming that when air is compressed or allowed to expand the heat generated or absorbed is the equivalent of the work done and of that only, no change being made in the internal energy of the air itself when the temperature is kept constant.
The subsequent researches of Dr Joule and Lord Kelvin (Phil.
The writings of Joule, which thus occupy the place of honour in the practical 'establishment of the conservation of energy, have been collected into two volumes published by the Physical Society of London.
On the theoretical side the greatest stimulus came from the publication in 1847, without knowledge of Mayer or Joule, of Helmholtz's great memoir, Ober die Erhaltung der Kraft, followed immediately (1848-1852) by the establishment of the science of thermodynamics, mainly by R.
P. Joule, Scientific Papers, pp. 46, 235; A.
Joule also made experiments upon iron wires under tension, and drew the erroneous inference (which has been often quoted as if it were a demonstrated fact) that under a certain critical tension (differing for different specimens of iron but independent of the magnetizing force) magnetization would produce no effect whatever upon the dimensions of the wire.
Experiments by Natanson on CO 2 at 17Ã‚° C. confirm those of Joule and Thomson, but show a slight increase of the ratio do/dp at higher pressures, which is otherwise rendered probable by the form of the isothermals as determined by Andrews and Amagat.
This inquiry yielded (in 1867) the result 783, and this Joule himself was inclined to regard as more accurate than his old determination by the frictional method; the latter, however, was repeated with every precaution, and again indicated 772.55 foot-pounds as the quantity of work that must be expended at sea-level in the latitude of Greenwich in order to raise the temperature of one pound of water, weighed in vacuo, from 60 to 61Ã‚° F.
Ultimately the discrepancy was traced to an error which, not by Joule's fault, vitiated the determination by the electrical method, for it was found that the standard ohm, as actually defined by the British Association committee and as used by him, was slightly smaller than was intended; when the necessary corrections were made the results of the two methods were almost precisely congruent, and thus the figure 772-55 was vindicated.
But it is to the physicists of the 19th century, and especially to Joule, whose experimental results were published in 1843-1849, that we practically owe the most notable advance that has been made in the development of the subject - namely, the establishment of the principle of the conservation of energy (see Energetics and Energy).
Joule's final result was 772.55 foot-bounds at Manchester per pound-degreeFahrenheit at a temperature of 62Ã‚° F., but individual experiments differed by as much as I %.
measure is equivalent to 4.177 joules per calorie at 16.5Ã‚° C., on the scale of Joule's mercury thermometer.
Trans.,1897, P. 381) Determined The Mechanical Equivalent Of The Mean Thermal Unit Between OÃ‚° And IooÃ‚° C., On A Very Large Scale, With A Froude Reynolds Hydraulic Brake And A Steam Engine Of Ioo H.P. This Brake Is Practically A Joule Calorimeter, Ingeniously Designed To Churn The Water In Such A Manner As To Develop The Greatest Possible Resistance.
Joule'S Scientific Papers (London, 1890); Ames And Griffiths, Reports To The International Congress (Paris, 1900), " On The Mechanical Equivalent Of Heat," And " On The Specific Heat Of Water"; Griffiths, Thermal Measurement Of Energy (Cambridge, 1901); Callendar And Barnes, Phil.
Assuming dH/do = 0.305 for saturated steam, he found that S was nearly independent of the pressure at constant temperature, but that it varied with the temperature from o 387 at 100Ã‚° C. to o 665 at 160Ã‚° C. Writing Q for the Joule-Thomson " cooling effect," dO/dp, or the slope BC/AC of the line of constant total heat, he found that Q was nearly independent of the pressure at constant temperature, a result which agrees with that of Joule and Thomson for air and COs; but that it varied with the temperature as (1/0) 3.8 instead of (i/0) 2.
Unlike the frictional generation of heat due to the resistance of the conductor, which Joule (1841) Table I.-Thermoelectric Power, p=dE/dt, IN Microvolts At 50Ã‚° C. Of Pure Metals With Respect To Lead.
A force of 1 Newton moving 1 meter requires 1 joule of energy.
The size of jar commonly known as a quart size may have a capacity from 4 o 0 th to s 00 oth of a microfarad, and if charged to 20,000 volts stores up energy from a quarter to half a joule or from -ths to Iths of a foot-pound.
With an apparatus similar to the above, but smaller, made of iron and filled with mercury, Joule obtained results varying from 772.814 foot-pounds when driving weights of about 58 lb were employed to 775.352 foot-pounds when the driving weights were only about 192 lb.
By ca-sing two conical surfaces of cast-iron immersed in mercury and contained in an iron vessel to rub against one another when pressed together by a lever, Joule obtained 776.045 foot-pounds for the mechanical equivalent of heat when the heavy weights were used, and 774.93 foot-pounds with the small driving weights.
For a long time the final result deduced by Joule by these varied and careful investigations was accepted as the standard value of the mechanical equivalent of heat.
Bidwell's results for iron and nickel were confirmed, and it was further shown that the elongation of nickel-steel was very greatly diminished by tension; when 2 Joule believed that the volume was unchanged.
This test was applied by Joule in the well-known experiment in which he allowed a gas to expand from one vessel to another in a calorimeter without doing external work.
319; Joule, Phil.
Joule failed to observe any change of temperature in his apparatus, and was therefore justified in assuming that the increase of intrinsic energy of a gas in isothermal expansion was very small, and that the absorption of heat observed in a similar experiment in which the gas was allowed to do external work by expanding against the atmospheric pressure was equivalent to the external work done.
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