Energy Joule experiment

One can also do work by stirring, e.g. by driving a paddle wheel as in the Joule experiment above. If tire paddle is taken as part of the system, the energy input (as work) is detemiined by appropriate measurements on the electric motor, falling weights or whatever drives the paddle. 

A unit capable of producing higher energies was used for the 8- and 10-joule experiments. Gases produced by the flash and laser irradiations were analyzed by mass spectrometry after fractionation using the following baths liquid nitrogen, dry ice, ice water, water at room temperature, and water at 60° C. 

The differences between the two forms of energy, heat and work, provide some insight into the second law. In an energy balance, both work and heat are included as simple additive terms, implying that one unit of heat, a joule, is equivalent to the same unit of work. Although this is true with respect to an energy balance, experience teaches that there is a difference in quality between heat and work. This experience is summarized by the following facts. 

The internal energy of a given mass of gas is independent of the volume occupied As a matter of fact (as shown by the porous plug experiment, which we will consider later), any actual gas only approximates to this statement There really was a very slight change m temperature in the bath in the Gay-Lussac-Joule experiment, though the methods employed were not sufficiently delicate to indicate it... 

D2.5 In the Joule experiment, the change in internal energy of a gas at low pressures (a perfect gas) is zero. 

But it was not until J. P. Joule published a definitive paper in 1847 that the ealorie idea was abandoned. Joule eonelusively showed that heat was a form of energy. As a result of the experiments of Rumford, Joule, and others, it was demonstrated (explieitly stated by Helmholtz in 1847), that the various forms of energy ean be transformed one into another. 

Joule s interest in the conservation of energy developed as a consequence of some work he did in his teens on electric motors. In 1841 he proposed, on the basis of his experiments, that the rate at which heat Q... 

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. 

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. 

An explanation of potential energy involves an explanation of force both terms are simply another way of saying that we know nothing about the thing to be explained. A distinct advance is made when a force can be explained in terms of the kinetic energy of a system in motion, an illustration of which is afforded by the kinetic theory of gases, which replaced the supposed forces of repulsion between the molecules of gases (the existence of which is disproved by Joule s experiment, 73) by molecular impacts. 

The first law of thermodynamics states that energy may be converted between forms, but cannot be created or destroyed. Joule was a superb experimentalist, and performed various types of work, each time generating energy in the form of heat. In one set of experiments, for example, he rotated small paddles immersed in a water trough and noted the rise in temperature. This experiment was apparently performed publicly in St Anne s Square, Manchester. Joule discerned a relationship between energy and work (symbol w). We have to perform thermodynamic work to increase the pressure within the tyre. Such work is performed every time a system alters its volume against an opposing pressure or force, or alters the pressure of a system housed within a constant volume. 

The student used the ratios in Mixture I and ran the experiment at two different temperatures. Calculate the rate, the rate constant, log k and 1/T for each temperature studied. From the data, plot k versus 1/T and determine the activation energy. Given that the activation energy for the reaction is 8.6 x 104 Joules, calculate the % error. 

The procedure may start with the reference experiment, which, in the case under analysis, involved a solution of ferrocene in cyclohexane (ferrocene is a nonphotoreactive substance that converts all the absorbed 366 nm radiation into heat). With the shutter closed, the calorimeter was calibrated using the Joule effect, as described in chapter 8, yielding the calibration constant s. The same solution was then irradiated for a given period of time t (typically, 2-3 min), by opening the shutter. The heat released during this period (g0, determined from the temperature against time plot and from the calibration constant (see chapter 8), leads to the radiant power (radiant energy per second) absorbed by the solution, P = /t. ... 

The highest acetylene content observed in our studies was 25.9%. This value was found for the experiment in which 5 bursts of 10 joules energy were used to irradiate a cube of coal (Table III). The distribution of the hydrocarbons obtained in this experiment is given in Table IV, showing that acetylene accounted for approximately 91% of the hydrocarbon product. 

The table below shows the maximum kinetic energy (in electron volts) of electrons emitted in a photoelectric experiment, for various wavelengths of radiation. By plotting the electron energy in joules against the frequency of radiation, show that these data support Einstein s prediction (eqn 1.13), and use them to obtain a value for Planck s constant. 

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