Reversible Definition and 240 Threads

Homework Statement I have two problems. What is Delta U, Delta H, q, and w for the Reversible heating of an ideal gas at constant P. Also, what are these values for the Reversible cooling of an ideal gas at constant V. Homework Equations The Attempt at a Solution For the...

Homework Statement Calculate the work done during the isothermal reversible expansion of a gas that satisfies the virial equation of state. Homework Equations Virial equation of state: pVm = RT(1+B/Vm + C/Vm + ...) Isothermal reversible expansion: w = -nRT ln(Vf/Vi) The Attempt at a...

In a "Briefer History of Time" Hawking says what everybody else does: that the laws of physics do not indicate a preference for time running forward or backward. He says that the forward direction may be required somehow by the increase of entropy from the highly ordered state of the...

Does anyone know if there is a relationship between the requirement in Quantum Computing that logic gates be reversible and the requirement in Quantum Mechanics that observables have to be self-adjoint?

i want to ask why heat transfer is considered ti be an irreversibility and why in carnot carnot cycle heat addititon is at constant temperature to make this process reversible

I am confused about the entropy change for reversible and irreversible cycles. I know entropy is a state function, so for cycles, the entropy change within the system should be 0, since the process ends up in the same state as the beginning. So does this mean that the entropy change for the...

Homework Statement A heat engine takes 4.0 moles of an ideal gas through the reversible cycle abca, on the pV diagram, as shown. The path bc is an isothermal process. The temperature at c is 600 K and the volumes at a and c are 0.04 m^3 and 0.10m^3, respectively. The molar heat capacity at...

Hi there, I found it is too much concepts in my head after reading more and more about thermodynamics. In the very beginning of the text, it emphize that in many cases (at lease in beginning level), we only deal with the equilibrium state in thermodynamic system. To make sure every stage of...

I learned Thermodynamics long time ago, forgot most of the content. I just want to ask I question. For a reversible engine, no matter how many complete cycles it done, the total change of entropy of the engine will always be ZERO, right? What about the change of entropy of the universe in...

I am not able think of convincing answers to the following questions- 1.Why the distance between knife edges (when the time periods about them is approx same) is considered equal to the length of an equivalent simple pendulum ?? It will be great if you can derive it... 2. Why the ends of the...

Homework Statement A reversible composite heat engine operates between three reservoirs at temperatures of 400K, 300K and 200K. One engine operates between the 400K and 300K reservoirs and a second engine operates between the 300K and 200K reservoirs and is synchronised with the first. In...

maximum work during reversible process? I have seen maximum work is achievable when the process is carried out reversibly. Is it correct? For example, if you look at the following problems, 1) Ten litres of an ideal gas at a pressure of 10 atm expands isothermally against a constant...

I need to find the equation for the work of a reversible isothermal compression of 1 mol of a gas in a piston/cylinder assembly if the molar volume of the gas is given by V= ((RT)/P) + b where b and R are positive constants. Not sure what to do .. please help! THANKS

I am having trouble with this question...It is from "applied thermodynamics for engineering technologists" by Eastop (Q5.2 if anyone has it)... The Question: Two reversible heat engines operate in series between a source at 527°C and a sink at 17°C. If the engines have equal efficiencies and...

A fluid at 0.7bar occupying 0.009m3 is compressed reversibly to a pressure of 3.5bar according to a law pv^n = constant. The fluid is then heated reversibly at constant volume until the pressure is 4bar; the specific volume is then 0.5m3/kg . A reversible expansion according to a law pv^2 =...

Equation apply to reversible only or not?? My thinking must be faulty somewhere, but I can't work out what's gonig on... The equation Tds = du + pdv and du = dq + dw are supposed to be valid for all processes right? yet dw = -pdv only for reversible cases, yes? So how do you...

So, I am looking a question about adiabatic expansions and the associated entropy changed. Why exactly is the change in entropy for a reversible adiabatic expansion/compression equal to zero? The book says its because there is no heat transfer, but for irreversible adiabatic processes, there...

Hi! I was just wondering if in a reversible isothermal process, there is a change in internal energy. I know that for the isothermal forward process the temperature is constant so internal energy is constant? What really stumps me is the word reversible.

Is evry mechanical process or mechanism reversiible? By that i mean to say, Can we carry out every mechanism or process in reverse? for eg: if i have a mechanism which converts rotary motion to oscillatory, can i use the same mechanism for changing the oscillatory motion to rotary, without...

Hi, I have some questions regarding thermo: 1) Does an isentropic process have to be a quasistatic one? What is the relation between equilibrium and reversibilty? 2) Naturally, there are revesible processes involving control volumes. A gas can go through an isentropic process in a reversible...

Homework Statement A sample of 2.00 mol. CH3OH (g) is condensed isothermally and reversibly to liquid at 64*C. The standard enthalpy of condensation of methanol @ 64*C is -35.3 kJ/mol. Find w and q for the reaction. Homework Equations w = -nRT * ln(Vf/Vi) (although I don't have volume...

how can we determine if a reaction is reversible or not? Zn2+ (aq) + 2e- -> Zn(s) is this a reversible reaction? thanks! :biggrin:

Homework Statement A pot is half filled with water and concealed by a lid so that no vapor can escape. The pot is then heated on a stove so steam is formed inside the pot. Now the heat is turned off and the vapor condenses into water. Explain when the process is reversible/irreversible. The...

please explain me in easy words . what is reversible and irreversibe process and give some daily examples. thank you.

Does anyone know where I can find information on these kinds of reactions such as the possible chemical combinations, reactions and decomposition temperatures, energy stored and released per unit mass, etc? Thanks! -Brendan

Hi, everyone. i have several questions about thermodynamics which I just read. 1. Why does a reversible process require equilibrium of the system all the time? 2. Is every process reversible if it's very very slow so that the system is in equilibrium all the time( and there's no friction...

Why is it when the conditions are adiabatic and reversible about a turbine, the assumption is its isentropic?

An ideal gas undergoes a reversible, cycli process. First it expands isothermally from state A to state B. It is then compressed adiabatically to state C. Finally, it is cooled at constant volume to its original state, A. I have to calculate the change in entropy of the gas in each one of the...

(I think I've actually asked this before...):blushing: I have a standard 3 speed reversbile ceiling fan. The reverse switch of course changes it from blowing air up to blowing air down. What is the benefit of reversing the fan? Most people seem to think that it constitutes a difference...

A cyclic machine receives 325 kJ from a 1000 K energy reservoir. It rejects 125 kJ to a 400 K energy reservoir, the cycle produces 200 kJ of work as output. Is this cycle reversible, irrerversible, or impossible? Not exactly sure what he is looking for here. But, since W=QH-QL, does that mean...

I didn't catch yet the difference between an incomplete and a reversible reaction. I think they are the same. Or there is any reaction that is incomplete but not reversible? Or one that is reversible but not incomplete?

we have an ideal monatomic gas which intially occupies 27*(10^-3) m^3 at a pressure of 3.2*(10^5) Pa and at a temperature of 400K. We have to find the heat supplied to the gas, the work done on it, and its increase in internal energy when it is compressed isothermally at 400K to a volume of...

It is stated that the change in entropy of an isolated system during an irreversible process is > 0; while for a reversible process, it is = 0. An isochoric process has a change in entropy given by : nC[SIZE="1"]v(P[SIZE="1"]f/P[SIZE="1"]i). Does this mean that it is an irreversible process...

for the following question: a reversible heat engine, opearting in a cycle, withdraws heat from a high-temperature reservoir(the temperature of which consequentyly decreases), performs work w, and rejects heat into a low-temperature reservoir(the tempertaure of which consequentyly increases)...

I often hear people suggest switching the direction of a ceiling fan from 'blow' to 'suck' or the reverse, thinking that one will draw cool air in better. My intuition tells me that: - a ceiling fan blows air in a doughnut patterrn, where air flows either up in the centre or down in the...

This regards an article found in the journal of Nature, 26 Aug. '04. I thought it might be interesting, not so much for the physics it presents (although they are certainly fascinating) but because of the implications. I think a discussion around the questions provided at the end of this essay...

It's probably a silly question. I know definitions of quasistatic and reversible process. How can we proove that each quasistatic process is reversible? Before it went for me without saying. But now I noticed that I can't proove it. In books that I have this conclusion is made after both...

A perfectly reversible heat pump heats a building at 20deg from the atmosphere at 5deg. If the heat pump is run by an electrical motor whose efficiency is 80%, what is the cost of 1KWhr of heat supplied? (1KWhr of electricity is 6p) I am confused by this qn as I thought the efficiency, e =...

why is it acceptable to assume any heat exchanged with the surroundings of a system is a reversible heat exchange? The only explanation I can find is that it's because the surroundings are essentially unchanged by the heat they absorb...but I don't understand that as an explanation. I take...

is radioactivity decay reversible or irreversible?