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Topic: Reversible process (thermodynamics)

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	Reversible process (thermodynamics) - Wikipedia, the free encyclopedia
		A process that is not reversible is termed irreversible.
		A reversible process changes the state of a system in such a way that the net change in the combined entropy of the system and its surroundings is zero.
		Reversible processes define the boundaries of how efficient heat engines can be in thermodynamics and engineering: a reversible process is one where no heat is lost from the system as "waste", and the machine is thus as efficient as it can possibly be (see Carnot cycle).
	en.wikipedia.org /wiki/Thermodynamic_reversibility (480 words)

	ch.5 definitions
		Carnot cycle - A Carnot cycle is a reversible cycle first proposed by Sadi Carnot, and is composed of four reversible processes, among which two are isothermal and two are adiabadic, and it can be executed either in a closed or a steady-flow system.
		In a reversible process, the ratio of the heat associated with the high temperature to the heat associated with the low temperature is equal to the ratio of the high temperature over the low temperature.
		thermodynamic temperature scale - The thermodynamic temperature scale is a temperature scale that is independent of the properties of the substances that are used to measure temperature.
	www.ocf.berkeley.edu /~ssoong/me105/definitions/me105_5.html (985 words)

	Second Law of Thermodynamics
		Thermodynamics is a branch of physics which deals with the energy and work of a system.
		Thermodynamics deals only with the large scale response of a system which we can observe and measure in experiments.
		The first law of thermodynamics defines the relationship between the various forms of energy present in a system (kinetic and potential), the work which the system performs and the transfer of heat.
	www.grc.nasa.gov /WWW/K-12/airplane/thermo2.html (574 words)

	Thermodynamics
		Thermodynamics is the branch of physics involving heat and its conversion to other forms of energy and to work.
		Equilibrium in thermodynamics is static (unchanging) behavior, and a quasiequilibrium process is thus quasistatic.
		For irreversible processes, the path is often unknown and is shown as a dotted curve.
	www.innovatia.com /Design_Center/rktprop1.htm (2606 words)

	Creationism and Pseudo Science
		Thermodynamics is not limited to constant temperature conditions, but it is outside the scope of the present application to discuss the effect of temperature variation.
		A reversible process is one in which proceeds in such a manner that every step is characterized by a state of balance, in which the process could be reversed by an infinitesimal change in conditions.
		In a reversible process the entropy change in a system due to the action of the surroundings is equal and opposite in sign to the entropy change of the surroundings.
	www.fsteiger.com /thermo3.html (1559 words)

	Reversible Process Thermodynamic - Engineers Edge (Site not responding. Last check: 2007-10-13)
		A reversible process for a system is defined as a process that, once having taken place, can be reversed, and in so doing leaves no change in either the system or surroundings.
		Therefore, the reversible process is an appropriate starting point on which to base engineering study and calculation.
		Although not practical for real processes, this method is beneficial for thermodynamic studies since the rate at which processes occur is not important.
	www.engineersedge.com /thermodynamics/reversible_process.htm (243 words)

	ipedia.com: Thermodynamic reversibility Article (Site not responding. Last check: 2007-10-13)
		In thermodynamics a reversible process is a process in which the energy accumulated in the surroundings is exactly the same as the energy expended by the process with no losses due to friction or othe...
		In thermodynamics a reversible process is a process in which the energy accumulated in the surroundings is exactly the same as the energy expended by the process with no losses due to friction or other effects.
		A reversible process can be reversed at any point in the process by making a series of infinitesimal changes in the opposite direction of the original process.
	www.ipedia.com /thermodynamic_reversibility.html (307 words)

	[No title]
		Reversible processes are interesting because work-producing devices (such as a car engine) deliver the most work, and work-consuming devices demand the least work when the process is reversible.
		Factors that cause a process to be irreversible are called irreversibilities, and include friction, unrestrained expansion, chemical reactions etc. Entropy can be expressed as: EMBED Equation.3 where the equality holds for an internally reversible process, and the inequality for an irreversible process.
		However, in thermodynamics the term isentropic is customarily used in thermodynamics to imply an internally reversible, adiabatic process.
	www.tfd.chalmers.se /~jaf/Apm/Entropy.doc (648 words)

	thermo-2 (Site not responding. Last check: 2007-10-13)
		F. Second Law of Thermodynamics: In a reversible process, the entropy of the universe is constant.
		A reversible process is one in which the system and surroundings never differ by more than an infinitesimal amount.
		A reversible process may be made to go in either direction by infinitesimal changes in conditions.
	colossus.chem.umass.edu /chandler/ch112/thermo-2.htm (822 words)

	[No title] (Site not responding. Last check: 2007-10-13)
		The reverse process at the same temperatures is not spontaneous Water turning to ice is spontaneous at T
		0. Note: the second law states that the entropy of the universe must increase in a spontaneous process.
		Because the reaction is exothermic the entropy of the surroundings increases as the heat evolved increase the thermal motion of surrounding molecules.
	www.aui.ma /personal/~A.Ouardaoui/Lecture/chap19che1402SPO4.doc (603 words)

	Thermodynamics
		It must operate using reversible processes: a reversible process is one in which the system and the surroundings can be returned to state they were in before the process began.
		If energy is lost to friction during a process, the process is irreversible; if energy is lost as heat flows from a hot region to a cooler region, the process is irreversible.
		The efficiency of an engine using irreversible processes can not be greater than the efficiency of an engine using reversible processes that is working between the same temperatures.
	physics.bu.edu /~duffy/py105/notes/Thermodynamics.html (1413 words)

	Thermodynamics
		We will present some simple examples of these laws and properties for a variety of physical systems, although, as aerodynamicists, we are most interested in thermodynamics in the study of propulsion systems and high speed flows.
		Thermodynamic equilibrium leads to the large scale definition of temperature, as opposed to the small scale definition related to the kinetic energy of the molecules.
		This leads to the second law of thermodynamics and the definition of another state variable called entropy.
	www.grc.nasa.gov /WWW/K-12/airplane/thermo.html (358 words)

	The first law of thermodynamics
		As mentioned previously two of the thermodynamic variables p, V, and T are sufficient to fully specify the thermodynamic equilibrium state of a thermodynamic system since the third variable may be obtained from the equation of state.
		The name stems from the fact that such a process can always be reversed by reversing the external conditions that gave rise to the modified state of thermodynamic equilibrium.
		Such processes are irreversible in the sense that it is not possible to bring the system back to where it came from by reversing the sequence of time dependent external conditions which induced the process.
	www.pha.jhu.edu /~broholm/l35/node1.html (495 words)

	thermodynamics. The Columbia Encyclopedia, Sixth Edition. 2001-05
		The system is thermally insulated from the environment, and the first law of thermodynamics requires that the work done by or on the system be equal to the loss or gain of the system’s internal energy.
		For an ideal gas the internal energy depends only on the temperature; hence the internal energy remains constant during an isothermal change, and the heat absorbed from or by the reservoir is equal to the work done on or by the environment.
		This statement constitutes the first law of thermodynamics, which is a general form of the law of conservation of energy (see conservation laws).
	www.bartleby.com /65/th/thermody.html (1106 words)

	Thermodynamics (Site not responding. Last check: 2007-10-13)
		The basic ideas of thermodynamics are taught in high school physics classes, so the Wright brothers knew and used these concepts, particularly in their engine design.
		We will present some simple examples of these laws and properties for a variety of physical systems, although, as aerodynamicists, we are most interested in thermodynamics in the study of engine operation.
		The first law of thermodynamics relates the various forms of energy in a system (kinetic and potential) to the work which a system can perform and to the transfer of heat.
	wright.nasa.gov /airplane/thermo.html (380 words)

	thermodynamics, thermal & chemical process design evaluation & analysis - James F. Wright, PhD
		The field of Thermodynamics is one of the few self-contained areas of study in the physical sciences that is developed on the basis of only a moderate knowledge of mathematics (partial differential and integral equations).
		This is the thermodynamic statement for the fundamental principle of the Conservation of Energy.
		Second Law - The possibility or impossibility of the process A to B and B to A depends entirely on the nature of the states A and B at the beginning and end of the process.
	www.drjfwright.com /c/thermodynamics.html (881 words)

	[No title] (Site not responding. Last check: 2007-10-13)
		Thermodynamics Chemical Kinetics Thermodynamics is concerned with the energy changes that accompany chemical and physical processes.
		Thermodynamics can tell us whether a reaction will occur by itself or not, eventually.
		The first law of thermodynamics recognizes the impossibility of perpetual motion machines by stating that if a system undergoes some series of changes that ultimately brings it back to its original state, the net energy is zero.
	www.bsd405.org /teachers/Bonnc/ultimatethermo.DOC (325 words)

	Thermodynamics (Site not responding. Last check: 2007-10-13)
		Thermodynamics is an experimental science based on a small number of principles that are generalizations made from experience.
		From the principles of thermodynamics one can derive general relations between such quantities as coefficients of expansion, compressibilities, specific heat capacities, heats of transformation, and magnetic and dielectric coefficients, especially as these are affected by temperature.
		Thermodynamics is complementary to kinetic theory and statistical thermodynamics.
	www.termodynamics.com (427 words)

	The First Law of Thermodynamics
		These plots illustrate the effects of various degrees of reversibility on the amount of work done when a gas expands, and the work that must be done in order to restore it to its initial state by recompressing it.
		Only when the processes are carried out in an infinite number of steps will the system and the surroundings be restored to their initial states— this is the meaning of thermodynamic reversibility.
		Since most processes that occur in the laboratory, on the surface of the earth, and in organisms do so under a constant pressure of one atmosphere, Eq 5 is the form of the First Law that is of greatest interest to most of us most of the time.
	www.chem1.com /acad/webtext/energetics/CE02.html (2408 words)

	Time [Internet Encyclopedia of Philosophy]
		The asymmetry is due to the fact that outgoing processes from a common center tend to be correlated with one another, but incoming processes to a common center are uncorrelated.
		The arrow of time that was absent in the reversible process of the microscopic movie would be evident in the irreversible process of the macroscopic movie.
		He showed that irreversible macroscopic thermodynamic processes are irreversible because the probability of their actually reversing is insignificant.
	www.iep.utm.edu /t/time.htm (15799 words)

	Thermodynamics
		That’s why thermodynamics, which is generally a mechanical engineering course, is usually required for graduation with a mechanical, electrical, civil, or chemical engineering degree.
		Thermodynamics is, from an engineer’s point of view, the ultimate science.
		In real life there are some nearly reversible processes; but the Third Law (which we will see in a moment) says that there are no truly reversible processes.
	www.ridgenet.net /~do_while/sage/v7i1f.htm (1850 words)

	Thermodynamics \| Chapter Glossary
		is stated as the entropy change of a system during a process is equal to the net entropy transfer through the system boundary and the entropy generated within the system as a result of irreversibilities.
		is entropy generated or created during an irreversible process, is due entirely to the presence of irreversibilities, and is a measure of the magnitudes of the irreversibilities present during that process.
		is expressed as the entropy of an isolated system during a process always increases or, in the limiting case of a reversible process, remains constant.
	highered.mcgraw-hill.com /sites/0072383321/student_view0/chapter6/chapter_glossary.html (799 words)

	Thermodynamics and solution behavior of macromolecules (Site not responding. Last check: 2007-10-13)
		Thermodynamics is concerned with changes in equilibrium processes and determines the direction a process is taking, but not its kinetics, i.e., how long it takes for the process to finish.
		Thermodynamic laws are concerned with the relationship between those parameters of a system and are given as mathematical equations.
		Reversibility is normally achieved when changes occur in very small steps (indicated by the differentials dq and dw etc..) and close to equilibrium.
	www-biology.ucsd.edu /classes/bibc110.SU99/part1/reader.html (7513 words)

	BIOPHYSICS 354
		, which define the reversible process, are of special importance in thermodynamics, because, unlike the work and heat exchanged in an irreversible (or "spontaneous") process, they have unique values for a defined change in state; they are variables of state.
		The process must (in principle) be able to perform useful work on the surroundings, if a suitable coupling process is available.
		From this it is obvious that if a process occurs in which the system is returned to its initial state, the values for changes in the variables of state are zero (the cyclic integral for dG, dA, dH, etc. is 0).
	www.life.uiuc.edu /crofts/bioph354/thermo_lesson.html (1043 words)

	Gibbs free energy
		The Gibbs free energy determines outcomes such as the voltage of an electrochemical cell, and the equilibrium constant for a reversible reaction.
		Any natural process occurs if and only if the associated change in G for the system is negative, i.e.
		Thus, thermodynamic processes are not confined to the two dimensional P-V diagram.
	www.brainyencyclopedia.com /encyclopedia/g/gi/gibbs_free_energy.html (542 words)

	[No title]
		In an isothermal process the temperature remains constant; therefore, the internal energy of an ideal gas remains constant throughout an isothermal process.
		If the process is irreversible, the only possible choice for the change in the entropy of the rest of the universe is +10 J/K; this results in a total entropy change of +5 J/K for the universe.
		For segment BC, the process is isobaric, that is, the pressure is constant.
	www.fiu.edu /~tgarcia/teaching/phy2053/ch15.doc (2395 words)

	Reversibility (Site not responding. Last check: 2007-10-13)
		In a reversible process the state of working fluid and system's surroundings can be restored to the original ones.
		A reversible process between two states may be shown by a continuous curve on any diagram of properties.
		Intermediate states for an irreversible process is indeterminate, therefore these processes are often shown by a dotted line joining the initial and final states.
	www.taftan.com /thermodynamics/REVERSIB.HTM (217 words)

	[No title] (Site not responding. Last check: 2007-10-13)
		Thus, for a reversible, adiabatic process EMBED Equation.3 A constant entropy process is referred to as isentropic.
		For a reversible, isothermal process, the temperature T is constant.
		For processes where water or steam is the working fluid, we can draw the Temperature-Entropy (T-s) diagram for the process, in a similar manner as the T-v diagram.
	www.eng.abdn.ac.uk /courses/eg2539/secondlaw.doc (918 words)

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