Entropy Definition and 1000 Threads

Let's think about two thermal reservoirs. They are internally reversible. This means they don't have entropy generation(Sgen) right? Each reservoirs' entropy change is different; one is minus(-) and the other is plus(+). But total entropy change in the isolated system has plus value(entropy...

Lets say we have T1. From a reservoir 4000K, Q is added and that makes the temperature T2. How do we calculate the entropy generation in a process like that? Isn't it Sgen=S2 - S1 - (Q/T) But which temperature we will use in the (Q/T)? T1, T2 or 4000K?

Homework Statement A hot gas stream at 600K and 200 kPa is cooled at constant pressure to 300K in a pipe by direct thermal contact with the atmosphere. The mass flow rate of the stream is 0,1 kg/s and the atmospheric temperature and pressure are 300K and 100 kPa. Modeling the gas as an ideal...

Homework Statement What is the entropy change of the universe as a result of the following processes: (a) a 1μF capacitor is connected to a 100V electrochemical cell at 0°C, (b) the same capacitor after being charged to 100V is discharged through a resistor kept at 0°C? Homework Equations...

Hi, I know that changes in entropy can be expressed as a function of temperature, specific volume, and pressure using the fundamental equations of thermodynamics: ds = du/T+pdv/T, where the changes in entropy can be caused by either changing the specific volume or the internal energy. I also...

Hello everyone, I still wonder if there's a change in entropy in adiabatic process. The definition of entropy is a quantity represents for the disorder state of a system. Arccording to kinetic theory of gas, temperature is for the state of chaotic motion of molecules. So I'm very confuse, can...

Homework Statement to illustrate an aspect of the second law of thermodynamics, we regard entropy changes in two cases. We have a vessel with 1 kg of warm water with T = 80 C and another vessel with 2 kg of cold water with T = 10 C and we mix them. Case 1: we pour hot water in the vessel with...

I am having an issue with finding the entropy in my program. I was asked to the find the entropy of the distribution as a function of time but i do not know where to start with entropy. I understand entropy but putting it in my program is where I am stuck Here is my code: # -*- coding: utf-8...

Homework Statement Show that the internal energy at constant entropy and volume decrease for a spontaneous process Homework Equations F = U-TS The Attempt at a Solution Use Clausius: dS-dQ/dT > 0 Assume constant volume: TdS > dU assume constant entropy this becomes 0>dU Since dU is...

I am reading a book called 'quantum processes systems and information' and in the beggining a basic idea of information is set out in the following way. If information is coded in 'bits', each of which have two possible states, then the number of possible different messages/'values' that can be...

Suppose we have an insulated cylindrical container with a piston inserted from one end. Suppose the volume confined by the piston is full of a hot gas. Now let the gas drive the piston so that the volume is increased. Did the entropy of the system decrease because some of the energy of the...

Homework Statement Is it possible to calculate the work done heat transfer, and efficiency of an object in a thermodynamic system, given the Temperature vs Entropy graph? Example: Homework Equations ∆U=Q-W ∆S=dQ/T e=1-(Qc/Qh) e=W/QhThe Attempt at a Solution Since this is a T vs S diagram,i...

How can I prove that the entropy change is intrinsically positive? Given two systems with both of the heat capacities are independent of temperature.

Recently an interested undergrad has asked me to explain holography to her. I know I'm not the best one to do that and I don't know that much, but for now, I'm the best she can have. Poor girl! Anyway, I figured its better to start from the entropy bound and explaining that the maximum amount of...

Homework Statement A heat engine operates between a high-temperature reservoir at 634 K and a low-temperature reservoir at 320 K. In one cycle, the engine absorbs 6540 J of heat from the high-temperature reservoir and does 2200 J of work. Homework Equations What is the magnitude of the net...

According to general relativity, time is a dimension, one of four dimensions that form 4D spacetime - a structure which is mathematically symmetrical and homogeneous. Should not all four dimensions, therefore, be mathematically interchangeable? Assuming that we are 3-dimensional bodies...

Homework Statement A 0.2 m^3 steel container that has a mass of 30 kg is filled with liquid water. Initially both the steel tank and the water are at 50°C. Now heat is transferred, and the entire system (i.e., steel and water) cools to the surrounding air temperature of 25°C. Determine the...

I am by no means an expert in physics being largely self taught (day job is a medical student) but have an avid interest in trying to understand the fundamental nature of our universe. In doing so I'm currently reading the book "Trespassing on Einstein's Lawn" by Amanda Gefter and came across...

Even though entropy is a state function and thus independent of path why is it that the definition of entropy is restricted to a reversible process? Eq 1: dS=dqrev/T First of all, is this for an open system, closed system or isolated system? The Clausius inequality deals with the exchange...

Hey Guys! Anyone able to help out here? I have already happily solved for T2 = 369.91K and m2 = 11.492kg However, for question 2.3, I'm terribly stuck. I'm not even sure what to make my control surface. How can I relate pressure outside the valve with the two thermodynamic states I have...

I was watching a Youtube video and the narrator mentioned that sometimes antimatter can be thought of matter traveling backwards in time and that confused me. I started thinking about what time is and it doesn't make any sense that antimatter acts in any way like it's traveling backwards in...

1 kg of iron with the temperature of 323 K to 293 K is cooled by dipping into a large water bath temperature of 293 K. What is the total entropy change?Relevant equations dS = mcdT/T S=mc *ln(T2/T1) C iron = 450J/(kgK) C water= 4200 J/(kgK) m water = I see in my book 1 kg in solution The...

hey guys,Entropy is supposed to be a measure of disorder in a a system then why is the formula ∫dQ/T used.I can understand why entropy increases with the energy in the system but why is the absolute temperature of the system relevent, is it a proportionality constant ? please enligthen me on...

Thermodynamics question: Why does the internal energy have a lower bound? I tried to explain it using postulates, but cannot get the connection between the postulates. Please do explain it briefly. Thank you.

Moderator's Note: THIS HOMEWORK WAS POSTED IN ANOTHER FORUM, SO THERE IS NO TEMPLATE. calculate the change in entropy suffered by 2 moles of an ideal gas on being heated from a volume of 100L at 50C to a volume of 150L at 150C. for the gas Cv=7.88 cal/moleC. I'm really confused in entropy and...

Homework Statement Compute the entropy change of 5.00 g of water at 100°C as it changes to steam at 100°C under standard pressure. Homework EquationsThe Attempt at a Solution 5/100+100 is what i did and my teacher says its wrong 'cause its in the formula

When I download a book to my Kindle, does the total entropy of the device decrease. I would think so.

How is entropy related to flow velocity? Does entropy change with when flow velocity changes ? I have a questions to solve with determines pressure, temperature and flow velocity at two points and Flow Direction is required to determine. Please help me with the question

Homework Statement An ideal diatomic gas is initially at temperature ##T## and volume ##V##. The gas is taken through three reversible processes in the following cycle: adiabatic expansion to the volume ##2V##, constant volume process to the temperature ##T##, isothermal compression to the...

Given enough time Boltzmann freak structures will appear, assembled from drifting matter, in the maximum-entropy universe if it is static, I.E. not expanding to eventually sweep all matter into the far horizon. In a lecture...

I stumbled upon this article (among many other similar ones) http://arxiv.org/abs/0909.3983, that seems to correct the outdated assumption that the CMB dominates the entropy density of the universe. They find that super massive black holes are actually the primary contribution by many orders of...

I'm trying to measure now much non redundant (actual) information my file contains. Some call this the amount of entropy. Of course there is the standard p(x) log{p(x)}, but I think that Shannon was only considering it from the point of view of transmitting though a channel. Hence the formula...

A pioneer. http://blogs.scientificamerican.com/cocktail-party-physics/in-memorium-jacob-bekenstein-1947-2015-and-black-hole-entropy/

Entropy of any system is state dependent. I just read about thermodynamics and I got this question. I first set my system which contained my classroom, the hallway connecting my physics teacher's cabin and the classroom. Then let the entropy of the system be S when I was going to the classroom...

How does the universe so conspire such that ΔS≥0, entropy increases?

I get that a Lie group like E8 is smoothly differentiable. But as I understand it, it has dimension and structure. Does it support the Idea of a phase space, and an entropy measure for that phase space, or at least for regions of it?

Please help me with my confusion. My logic: 1. CP violation causes direct T-violation 2. T-violation breaks Kirchhoff's law of thermal radiation (imagine a rock in a thermal bath of T-violating particles, where absorption and emission rates are different). When I say "radiation", I don't mean...

[Moderator's note: Recategorized thread to "Basic".] While driving alone through the beautiful scenery of Banff and Yoho national parks, a question formed in my mind. Which of these modes of slowing down a vehicle by an equal amount is likely to minimize the resulting overall increase in...

An old book I have on elementary Statistical Mechanics (Rushbrooke) uses as an especially simple case a system with one energy level. This level is doubly degenerate. The author doesn't give an example of such a system. Can anyone think of one? And would it have entropy k\ ln 2? [My thoughts...

[Mentor's Note: Thread moved from the New Member Introduction to General Physics] what are the physical interpertation of entropy?

Hi all, I was recently watching one of Susskind's 'Theoretical Minimum' lectures in which he says that the entropy of the universe may be measured via the number of observable photons, and that somehow these quantities (photon number and total entropy) are somehow linked. Could anybody with...

Homework Statement Man with a temperature of 310.15 K and a mass of 70 kg drinks 0.4536 kg of water at 275 K. Ignoring the temperature change of the man from the water intake (assume human body is a reservoir always at same temperature), find entropy increase of entire system. Homework...

Consider the problem of computing the entanglement entropy of two CFTs in the thermofield double state on identical finite intervals in 1+1 dimensions. The Euclidean path integral is then equivalent to computing the 2-point twist correlator on a torus. Given a central charge ##c##, does anyone...

how do we find change in entropy for two points on a P V diagram which are not an isotherm

I have been thinking about finding a way to define entropy on a rubik's cube. My idea is to use the number of cubies that are not in their solved position as the macrostate. This works well because there is exactly one way for all the cubies to be in the solved position so it has entropy of...

[Mentor's note: Edited to fix an error in the title] I hope to know where does this definition come from. Thank you very much.

I'm sorry for bad english. I wonder what is the differences between reversible-isothermal-expansion and irreversible-isothermal-expansion. Is their entropy same?

When I learned the concept of specific heat capacity, I knew that 1J/(K*kg) means that it takes 1 Joule of energy to increase the temperature of a kilogram of matter by one Kelvin, but what does J/K, the unit of entropy, mean?

I'm interested in the derivation of relativistic Boltzmann equation from entropy after reading Scott Dodelson's wonderful cosmology book. Does anyone know of any good readings for this? The usual way of doing things in classical mechanics is to assume \frac{dN}{dt}= 0 and go from there; but...

So i need a introduction to Heat, temperature and thermodynamics; not a very advanced text, just a clear beginner text that can include math/calculus. I'm just curious about how heat was/is measured, how it's defined and how it works.Also I wan't to understand thermodynamics and entropy and how...