Joule conversion

Table 1-7 provides a number of useful conversion factors. To make a conversion of an element in U.S. customary units to SI units, one multiplies the value of the U.S. customary unit, found on the left side in the table, by the equivalent value on the right side. For example, to convert 10 British thermal units to joules, one multiplies 10 by 1054.4 to obtain 10544 joules. 

Independent, and more accurate, quantification of the equivalence of work and heat came from an English physicist, James Prescott Joule, whose first publication in 1850 put the conversion rate at 838 foot-pounds and a later revision at 772 foot-pounds,... 

Having met Joule for the first time at the 1847 meeting of the British Association for the Advancement of Science in Oxford, Thomson initially accepted that Joule s experiments had shown that work converted into heat. Committed to Carnot s theory of the production of work from a fall of heat, however, he could not accept the converse proposition that work had been converted into heat could simply be recovered as useful work. Therefore, he could not agree to Joule s claim for mutual convertibility. By 1848 he had appropriated from the lectures of the late Thomas Young (reprinted in the mid-1840s) the term energy as a synonym for vis viva (the term in use at the time, traditionally measured as mtc) and its equivalent terms such as work, but as yet the term appeared only in a footnote. 

Your electric bill deals with a different unit of electrical energy called the kilowatt hour (kWh). The joule and the kilowatt hour are related through a simple conversion factor ... 

This equation can be used to calculate the energy change in joules, if you know Am in kilograms. Ordinarily, Am is expressed in grams AE is calculated in kilojoules. The relationship between AE and Am in these units can be found by using conversion factors ... 

That such a mechanical equivalent exists is a consequence of the fact that heat and work are interconvertible. The further fact that it is a fixed constant and independent of the process of conversion was proved by the experiments of Joule (1848-1880), referred to below. In the determination of this constant two measurements are required ... 

The entire agreement between the values of the mechanical equivalent of heat obtained by many different methods establishes the proposition that it is independent of the process in which the conversion of work into heat occurs, and depends solely on the choice of the units of these two magnitudes. This result was first established by Joule. 

The correctness of this statement is to be inferred from the exact agreement between the values of the mechanical equivalent of heat obtained by different methods. Thus, in Joule s second series of experiments, mechanical work is directly converted into heat in the first and third series, it is indirectly transformed through the medium of electro-magnetic energy in the fourth series, the energy of an electric current is converted into heat the identity of the values of J so obtained implies a complete conversion of the initial forms of energy into heat energy. 

Due to a fortuitous cancellation of units, volume can be expressed in cm3 and pressure in MPa to give the same results as volume in m3 with pressure in Pa, without invoking any conversion factors. Thus pV in Pa m3 gives Joules as does pV in MPa cm3. 

The only quantity considered here is the enthalpy of formation, A fH°, at 298.15 K. Data are given in units of kJmol-1. The conversion factor 1 thermochemical calorie = 4.1840 joules was used. 

Therefore, if we work in pascals and cubic meters, the work is obtained in joules. However, we might have expressed the pressure in atmospheres and the volume in liters. In this case, we may need to convert the answer (in liter-atmospheres) into joules. The conversion factor is obtained by noting that 1 L = 10 3 m3 and 1 atm = 101 325 Pa exactly therefore... 

The use of non-SI units is strongly discouraged. For these units there often do not exist standards, and for historical reasons the same denomination may mean sundry units. For example, it is common practice in theoretical chemistry to state energy values in kilocalories. However, to convert a calorie to the SI unit Joule, there exist different conversion factors ... 

France was a center for the development of thermodynamics, the study of heat and its conversion to other forms of energy. A few years before Ril-lieux s arrival in Paris, the French physicist Sadi Carnot had published his studies of steam engines and described the principles that became the second law of thermodynamics, placing fundamental limits on how efficiently heat can be used. Within a few years, James Prescott Joule of England would lay the basis for the first law of thermodynamics stating the equivalence of heat and energy. 

Holloway S. and Van Der Straaten R. The joul II project-The underground disposal of carbon dioxide. 1995 Energy Conversion and Management 36(6-9) 519-522. 

Where R is the gas constant (8-32 joules mol-1 deg 1), and A is a constant for the reaction—independent of temperature—that is related to the proportion of the total number of collisions between reactant molecules that result in successful conversion into products. The value... 

Concerning the Ka yield, the experimental works published in the last years showed a conversion efficiency of laser energy to Ka photons of 10 4-10-5, leading to a total number of 109-1010 Ka photons per joule of laser energy for each driving laser shot. As an example, Fig. 9.5 from [66] shows... 

Calculate the conversion factor for changing liter atmosphere to (a) erg, (b) joule, and (c) calorie. Calculate the conversion factor for changing atmosphere to pascal and atmosphere to bar. 

The Joule-Thomson coefficient p.jx, is positive when a cooling of the gas (a temperature drop) is observed because dP is always negative, p.j x, will be positive when dT is negative. Conversely, p.j x, is a negative quantity when the gas warms on expansion because dT then is a positive quantity. Values of the Joule-Thomson coefficient for argon and nitrogen at several pressures and temperatures are listed in Table 5.5. 

This is close to the simulated value of 2.57 W, including the irreversible, entropic, and Joule heat. The energy-conversion efficiency of this cell, defined as the ratio of the electric power (Jjvg VreiiA) to the total energy consumption IsvgVceuA + eat), is then calculated to be 40%. These simple calculations help demonstrate the validity and accuracy of a noniso-thermal PEFC model. 

From photolysis of methylene blue by ruby-laser giant pulses, Danzinger et al. found that a 0.5 Joule, 30 nsec laser pulse causes almost total conversion of the original molecules into transients, but that the photochemical change is completely reversible. The lifetimes of three transients have been measured as 2, 30 and 140 jusec resp. at a 5.5 x 10 M dye solution. 

For chemical reactions and phase transformations, the energy absorbed or liberated is measured as heat. The principal unit for reporting heat is the calorie, which is defined as the energy needed to raise the temperature of 1 gram of water at l4.5° C by a single degree. The term kilocalorie refers to 1,000 calories. Another unit of energy is the joule (rhymes with school), which is equal to 0.239 calories. Conversely, a calorie is 4.184 joules. The translation of calories to joules, or kilocalories to kilojoules, is so common in chemical calculations that you should memorize the conversion factors. 

Don t forget that both the calorie and Tins, joule are units of energy in published charts, so you will often have to do a conversion to obtain the unit that you want. 

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