Thermodynamic Definition and 502 Threads

Hi. I'm reading a solution to a problem concerning a gas of photons. In the solution, the energy of the gas is given as E=2\sum_{\vec{k}} \frac{\displaystyle \epsilon_{\vec{k}}}{\displaystyle \exp[\beta\epsilon_{\vec{k}}]+1} where \epsilon_{\vec{k}} is one photon's energy. It is said then...

Homework Statement Consider a model thermodynamic assembly in which the allowed (nondegenerate) states have energies 0, ε, 2ε, 3ε.The assembly has four distinguishable (localized) particles and a total energy U = 6ε. Tabulate the nine possible distributions of the four particles among the...

Hi! I am using a Zn-Mg alloy (52% and 48% respectively) as a phase change material in a thermal energy storage system, but I have been unable to track down important properties, such as specific heats and thermal conductivity. Is there any way to approximate these relatively accurately given...

This is more of a recurring conceptual doubt that I keep on running into when solving thermodynamics problems. We are taught that variations between extensive state variables in equilibrium are given by the following 'fundamental formula': dE = TdS + \mathbf{J}\cdot{d}\mathbf{x} +...

Homework Statement I have the data for a p-v diagram from experiment of a fluid (the fluid is unknown). The data is attached below as the crosses. It also has the approximated ideal cycle for that data. Does anyone know how to find the work done for this real experimental data? Maybe a MATLAB...

Mechanical Engineering Undergrad here: So this didn't seem explicitly like a homework question, but I was wondering how to describe a solar cell in terms of thermodynamics. If I had to model it with the first law of thermodynamics, I would consider it a simple loop of heat/work exchange...

Moving fluids are generally in a state of non-equilibrium. However, in fluid dynamics, people generally assume a state of local thermodynamic equilibrium and argue that in such a condition, equilibrium thermodynamic concepts such as pressure, temperature, entropy, internal energy etc. can be...

I don't understand of what a "thermodynamic entity" is?

Hi. Sorting the exchanges of heat and mechanical work in a thermodynamic cycle by the signs and summarizing, I get ##Q_{in}>0##: heat transferred into the system ##Q_{out}<0##: heat transferred to the cold reservoir ##W_{out}<0##: work done by the system ##W_{in}>0##: work done on the system...

Homework Statement A spherical drop of a pure substance floats on top of the vapor of the same substance so the system vapor+drop is isolated. The drop has a surface tension σ. Show that at the thermodynamic equilibrium PL≠PV and calculate the difference. Homework Equations Three laws of...

I am wondering how efficient this engine can get, I am thinking if one used a superconductive magnet that is really strong?

What is wrong with this logic, if any? It does not seem like this should be true but maybe I'm mistaken. Assuming the process consists of two isobaric processes and two isothermal processes the work from B to C in terms of p1, p2, V1, and V2 is given by the following. 1) WBC=p2(VC-VB) 2)...

When solving a word problem in Thermodynamics and are given both pressure and tempreature of a fluid or water, how do we know if we should get information about internal energy and entropy from the Pressure Table or the Temperature Table?

Homework Statement Prove that ##TdS = C_vdT + \alpha T / \kappa dV## Homework Equations ##T dS = dU - pdV## ##\alpha = \frac{1}{v}\left(\frac{\partial v}{\partial T}\right )_P## ##\kappa = -\frac{1}{v}\left(\frac{\partial v}{\partial P}\right)_T## The Attempt at a Solution The ##C_vdT## part...

Hello, for those who don't know me I'm layman with some knowledge at popular science level. Discussing with a friend we came to the following point and I would like to ask it here because we had doubts about our reasoning. Cramer's Transactional Interpretation proposes that, in a sense, a...

Cv = (∂U/∂T)v = T(∂S/∂T)v I can prove this by using the Maxwell relations, but I have trouble deriving it from the first law. dU = TdS - pdV (∂U/∂T)v = T(∂S/∂T)v + ∂S(∂T/∂T)v = T(∂S/∂T)v + ∂S Is there a problem with my derivation?

Homework Statement Given two indistinguishable objects at the same initial temperature ##T_i##, calculate the minimum work done by a refrigerator functioning between the two objects till one of the objects reaches a new temperature ##T_2##, assume constant heat capacities and constant pressure...

I have this question that in it there's this expression "A proper Thermodynamic system". I thought that means that the first law (or is it the second) that ##dS \ge 0##, i.e. the change of entropy always increase. But I am not sure, can someone clear to me this matter? Thanks in advance.

Homework Statement The internal Energy of a system is ##U=aP^2V## with a positive constant a. Find the adiabats of this system in the P-V plane. The solution is $$P=\frac 1 a\left( \sqrt{\frac {V_0} V}-1\right)$$ 2. The attempt at a solution the first law with the given internal energy...

Homework Statement A 0.350 kg sample is placed in a cooling apparatus that removes energy as heat at a constant rate. The figure below gives the temperature T of the sample versus time t; the horizontal scale is set by Ts = 80.0 min. The sample freezes during the energy removal. The specific...

Homework Statement A monatomic ideal gas undergoes the thermodynamic process shown in the PV diagram. Determine whether each of the values ΔU, Q, and W for the gas is positive, negative, or zero. Homework Equations ΔU=Q-W W=integral under the curve PV=nRT T=PV/nR The Attempt at a Solution...

Homework Statement Suppose you are given the following relation among the entropy S, volume V , internal energy U, and number of particles N of a thermodynamic system, where A is a constant.: $$ S = A(NVU)^{\frac 1 3} $$ Find the chemical potential μ(T,P) Homework Equations $$ \frac μ T =...

1. The problem statement, all variables and given/known Homework Equations show that a hydrogen gas cloud at 10000K is about twice as optically thick at the Balmer limit compared with the Paschen limit. Assume that the H atoms are in Local Thermodynamic Equilibrium, the Gaunt factor is unity...

An ideal gas at initial state has temperature 300 K has been compressed under constant pressure of 30 Pa from volume 3 cubic meters to 1.8 cubic meters. In the process 75 J of heat was lost. A. Find the change in internal energy B. Find the final temperature I tried two methods in A and they...

If space is expanding wouldn't that violate the first law of thermodynamics

Homework Statement An ideal gas with adiabatic index γ is taken around a complete thermodynamic cycle consisting of three steps. Starting at point A, the pressure is increased at constant volume V1 from P1 to P2 at point B. From point B to point C, the gas is allowed to expand adiabatically...

I'm nearly at the end of this derivation but totally stuck so I'd appreciate a nudge in the right direction Consider a set of N identical but distinguishable particles in a system of energy E. These particles are to be placed in energy levels ##E_i## for ##i = 1, 2 .. r##. Assume that we have...

Homework Statement (a)How much heat must be added to a block of 0.120kg of frozen ammonia initially at 100oC to convert it to a gas at 80oC given the following information? (b) assuming this could be done using a reversible process what would be the total entropy change associated with this...

Say you wanted to heat up your room. You could choose between an electric heater that outputs 500W or a PC that draws 500W. In both cases, the amount your room would heat up by would be the same, but the second case is much more advantageous because the computer can process information before...

Here I want to know how to find the heat interactions of non-ideal gases in the following processes. 1. Isobaric process 2. Isochoric process I know that internal energy U depends on temperature and volume. And the enthalpy depends on temperature and pressure. How calculation of heat...

Homework Statement Consider a rigid piston cylinder arrangement. Assume that the cylinder and the piston are covered by a perfectly insulating material and the piston cylinder interface is very smooth. Two types of ideal gases are separated in the cylinder by the piston. The number of gas...

hello there ! i found this while studying :the kinetic theory of gases. the thing is thermodynamics comes afterwards , and i found this

Can someone tell me the mathematical and physics background i need to perform ab initio calculations to determine thermodynamic properties of materials. I am a Mechanical engineer with a masters in Metallurgy

Homework Statement Two thermally insulated vessels are connected by a narrow tube fitted with a valve that is initially closed as shown in the figure below. One vessel of volume V1 = 15.1 L,contains oxygen at a temperature of T1 = 320 K and a pressure of P1 = 1.70 atm. The other vessel of...

Homework Statement I know that for constant volume ∂q=du and so du=Cv.dT However i don't understand how did we get to ∂q=du by neglecting the vdP term of enthalpy What I am trying to say is, is enthalpy this ∆U+P∂V+V∂P or this ∆U+P∂V? I don't understand since the definition of enthalpy is...

Homework Statement If an engine operates between 250°C and 25°C, what is its maximum thermodynamic efficiency?Homework Equations Ec=1-Tc/Th The Attempt at a Solution 1-25/250 =90% or 1-(25+273)/(250+273) =43% In this question,which one should I use K or ºC ? thank you

An alternative formulation of the second law is that the energy of the system U is minimised if the temperature and entropy of the system are held constant. However, dU= TdS -pdV which means that U is presumably constant if the volume V and the entropy S are kept constant. How then can U...

Hello all. I have a quick question about entropy... I've just been formally introduced to it. Consider the example of a metal block of mass m and heat capacity Cp at temperature T1 = 60C being dropped into a large lake of temperature T2 = 10C. $$\Delta S_{block} =...

Homework Statement Here is the problem: An inventor claims to have developed a heat pump that provides a 180 kW heating effect for a 293 K household while only consuming 70 kW of power and using a heat source at 273 K. Can this claim be possible? Homework Equations COP of heat pump = Qh/W COP...

I'm studynig thermodymamics using the textbook 'Thermodynamics foundations and applications' (Beretta and Gyftopopulos). The definition of a system according to the authors consist in the specification of : -the costituents of the system ( atoms or molecules or prottons neutrons ... in...

Homework Statement Calculate ∆rH° for the reaction c2h50h+3o2-->2co2+3h20 Given that ∆rU° = - 1373 kJ mol-1 at 298K. Homework Equations c2h50h+3o2-->2co2+3h20 The Attempt at a Solution delta H f CO2(g) = -393.5 kJ/mole delta H f H2O(l) = -241.8 kJ delta H f O2(g) = 0 these values are...

Perhaps not an appropriate place to ask this. I've completed a question which is phrased as the following: Explain, on thermodynamical grounds, why the minimisation of the energy E(S, V, N) yields the equilibrium state of a system with fixed entropy S, volume V and number of particles N. I...

I have to write an essay this semester for my thermo class on some current thermodynamic research. I'm currently doing some googling but does anyone here have any suggestion of something they interesting?

Homework Statement An amount of water substance having a mass of 1 kg is contained in a vessel at a pressure of 1 MPa. It is heated for some time after which the pressure is 3 MPa. The volume of the vessel is 0.1 m3. Assuming no work is done by or to the substance, calculate the final...

Homework Statement A system possesses three energy levels $$E_1=\varepsilon$$ $$E_2=2\varepsilon$$ $$E_3=3\varepsilon$$ with degeneracies $$g(E_1)=g(E_3)=1$$ $$g(E_2)=2$$. Find the heat capacity of the system. Homework Equations $$\beta=\frac{1}{kT}$$ $$Z=\sum_i g_ie^{-\beta \varepsilon_i} \...

Hi all, I actually work in physics (quantum physics) but my thermodynamics knowledge is a bit lacking these days. The following problem has had me puzzled for quite a long time. Basically, if I point the hot air coming out of a hairdryer at a target, will that target's temperature ever go...

In my text it was said that ΔH=ΔU+ΔnRT H:ENTHALPY U:INTERNAL ENERGY Δn:n of gaseous products-gaseous reactents they use ΔnRT instead of Δ(PV),here T is constant⇒U is a constant(U is a function of temperature) then why didn't the term ΔU became zero? what is the actual equation?is it is...

In the derivation of the Clausius inequality, T is the temperature of the reservoir at that point in the cycle, but in the definition of entropy it becomes the temperature of the system. This seems to work for a Carnot cycle, where the two are the same, but for other processes, such as an object...

Consider an electric motor with a shaft power output of 20 kW and an efficiency of 88 percent. Determine the rate at which the motor dissipates heat to the room it is in when the motor operates at full load. In winter, this room is normally heated by a 2-kW resistance heater. Determine if it is...

Why a closed system can't be called as a Controlled Volume system?