Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [thermodynamics]

Covers the study of (mostly homogeneous) macroscopic systems from a heat/energy/entropy point of view. Consider also using tag: [statistical-mechanics].

0
votes
0answers
13 views

Solving for work without being given pressure

The following is an MCAT question I'm not sure how to approach. We have to solve for work without being given pressure. This is how far I've gotten: F=PA, Thus, W=Fd, W=PAd. Ad=deltaV, so W=PdeltaV. ...
0
votes
1answer
27 views

Apparent temperature of the universe at relative speeds

Suppose you are in a vessel traveling at relativistic or near relativistic speed relative to your local galaxy--whatever is physically reasonable, and won't get rapidly torn apart by high energy ...
2
votes
0answers
18 views

What happens to topological insulators at finite temperature?

There is a similar question here, but I had a few things I wanted to ask. So basically pretty much all analysis/ theory of topological insulators is for pure wave-functions and conservative ...
1
vote
2answers
42 views

Thermodynamic description of few-body systems

How large should a system be to become thermal? Thermodynamic description is well-established for systems with large numbers (say, of order of $N_A\sim 10^{23}$) of constituents. Is there a "lower ...
0
votes
1answer
21 views

Doubts about the characteristics of a real gas

I was studying about ideal gases and the changes made in the ideal gas equations to transform it into the real gas equation. So firstly in the book they considered the effect of finite volume of the ...
0
votes
0answers
21 views

Confusion about the coefficient of surface tension and the relation between force and length of a body

I haven't found a software that can create 3d or 2d shapes filled with liquids so I posted this picture. I know that the p=2σ/r where p is the pressure that goes inside the liquid and I guess that σ ...
3
votes
2answers
56 views

Why does thermodynamics use the negative of the Legendre transform?

So I see how the negative Legendre transform is very helpful in interchanging dependencies and giving us the four different major thermodynamic potentials, from internal energy to Helmholtz, Gibbs, ...
0
votes
1answer
60 views

How has the Earth's air pressure varied over geological time scales?

It is estimated that the Earth is losing about $5 \times 10^7 kg$ per year. Most of it due to hydrogen loss. I suppose this has an impact on the pressure of the atmosphere in general. Thus, I am ...
0
votes
1answer
23 views

Entropy function additivity

I am reading Herbert Callen's book Thermodynamics, which proposes a postulatory treatment to the subject. The postulate number 3 states the properties of the "entropy" function, one of which is the ...
0
votes
1answer
37 views

Why is compressibility $\kappa=(1/\rho^2) \partial\rho/\partial\mu$?

I am currently studying Giamarchi's book "Quantum Physics in One Dimension". This book defines the compressibility as usual, $$\kappa=-\frac{1}{V} \frac{\partial V}{\partial P}$$ and with no ...
-2
votes
0answers
13 views

question on capacitor [on hold]

A capacitor of capacitance C is intially uncharged is connected with a battery of emf ε.Find the heat dissipated in the circuit during charging?
1
vote
0answers
13 views

What is the Spectral Form Factor?

In many papers in Random Matrix Theory [1-3] related to quantum chaos (and, in particular, to the SYK model) they analytically continuate the partition function of the system $Z(\beta)$ into $Z(\beta +...
1
vote
3answers
32 views

How is an Isobaric process consistent with the first law of thermodynamics?

Suppose there is an isobaric process whereby the volume of a gas decreases while the pressure of the gas remains constant. Work is done on the gas to compress it. Since the change in internal energy =...
0
votes
0answers
13 views

Is the standard deviation of thermal energy in a crystal lattice at room temperature well defined?

It is well known that the mean thermal energy available in a crystal lattice at room temperature is approximately equal to 0.026 eV. I'm curious if there is a well defined corresponding standard ...
0
votes
0answers
26 views

What is the value of cubic expansio coeffficcient for an ideal gas at 0°C? [on hold]

What is the value of cubic expansion coeffficcient($\beta$ ) for an ideal gas at 0°C? Here: $$\beta = \frac 1V(\frac{dV}{dT})_{pn}$$ Options are: 1) $3.66\times10^{-3}K^{-1}$ 2) $3.66\times10^{3}K^{...
0
votes
2answers
86 views

Which is positive? which is negative? about laws thermodynamics…from problem solve

1) A hot block of iron does 50 kJ of work on a cold floor. The block of iron also transfers 20 kJ of heat energy to the air. Calculate the change in energy (in kJ) of the iron block. 2) A chef ...
5
votes
2answers
68 views

Quantum Tunneling and Conservation of Energy

According to my understanding quantum mechanics, the probability of any particular particle in the universe being at any specific location in the universe is very small but never actually becomes zero....
1
vote
1answer
49 views

Difference in Sound and Heat

What makes sound and heat distinct ? The answer is said to lie in the fact that the former consists of vibration in an ordered fashion while the latter is not. But why would ordered vibration not be ...
-1
votes
1answer
20 views

What is the specific heat of steam, when Latent heat of vaporization decreases at the rate of $0.64 \:\rm Cal/K$ [on hold]

specific heat of water at $100° C = 1.01\:\rm Cal/gm$ degree, latent heat of vaporization decreases at the rate of $0.64\:\rm Cal/K$, latent heat of vaporization of $54\:\rm C \:Cal/gm$. What is the ...
1
vote
0answers
15 views

Does solid melt on the surface when the temperature is below its freezing point?

I have learnt at school that evaporation and condensation are always taking place (on the suface of a liquid) and that the vapor and liquid are in equilibrium. Does something similar happen on the ...
-1
votes
2answers
60 views

Proof for the first law of thermodynamics without calculus [on hold]

I want to find if there are ways of proving the adiabatic and polytropic process without using limits,differentiation or something that involves higher math.Is that possible? If not,why? I searched ...
0
votes
0answers
23 views

Reference request: good introduction to landau theory and phase transition

My background is in statistics, so I am not well versed in the details of physics, lattices, and ideal gases, etc.--beyond my high school familiarity. However, I have been looking at some models of ...
0
votes
2answers
32 views

Does increasing pressure increase or decrease latent heat of vaporisation?

I found some say increasing pressure increases the latent heat of vaporisation (What is the effect of an increase in pressure on latent heat of vaporization?). This doesn't make sense to me because ...
0
votes
1answer
41 views

Need verification for the entropy equation in statistical thermodynamics

The relationship between entropy $S$, the total number of particles $N$, the available energy levels $E_j$ and a yet to be defined parameter $\beta$ is: $$S(\beta)=k_B \cdot N \cdot \ln\bigg(\sum_{j=1}...
2
votes
1answer
46 views

Differentiating the Free Energy for the Chemical Potential

I wanted to ask a question about the partial differential of the Free Energy equation. I learnt to prove the Free Energy equation: \begin{aligned} \frac{F\left(N_{A}, N_{B}\right)}{k T}=& N_{...
0
votes
0answers
20 views

Lagrange Multiplier with inequality conditions

How can Lagrange multiplier method be used when inequality conditions are given instead of equality conditions?
0
votes
1answer
26 views

How big of a temperature difference is needed to power a thermoelectric generator?

I'm really curious about this and haven't been able to find a formula to calculate the types of voltages I could generate based on differences in temperature. An example of interest is The PowerPot ...
3
votes
2answers
68 views

Why is the Peltier / Seebeck Effect's efficiency so low in practical devices?

Usually solid state devices are able to attain excellent efficiency. However, currently existing Peltier coolers and Seebeck generators have horrible efficiency -- far worse than Carnot, and also far ...
0
votes
1answer
33 views

Statistical mechanics Calculating sums [on hold]

The energy is given by: $$ E(\sigma) = -\sum_{i=1}^{N}\sigma_i + a \sum_{i=1}^{N}\sigma_i^2 $$ where $a$ is constant. I have to calculate the following: $$\left\langle \frac{1}{N}\sum_{i=1}^{N}\...
-1
votes
0answers
27 views

Solid to Solid Vs Liquid to Solid Phase Transition [duplicate]

If we want to achieve Solid phase transition(means a solid transfer to another solid) and Liquid phase transition(means transformation of liquid into solid like water turned into ice..) then which one ...
1
vote
0answers
21 views

Semiconductor and temperature dependence

Does the conductivity of both intrinsic and extrinsic semiconductor increases with temperature or is it that conductivity of extrinsic semiconductor decreases with temperature just like a conductor ?
0
votes
1answer
28 views

Overestimation Problem [duplicate]

I had asked this problem earlier but I was too vague in how I asked it so I'm making a new post to be more specific. Problem: Say we have a series circuit with an ammeter, a cell with internal ...
52
votes
3answers
10k views

How does the Earth's center produce heat?

In my understanding, the center of the Earth is hot because of the weight of the its own matter being crushed in on itself because of gravity. We can use water to collect this heat from the Earth and ...
-3
votes
0answers
51 views

Solid to Solid Phase Transition and Liquid to Solid Phase Transition [on hold]

If we want to achieve Solid phase transition(means a solid transfer to another solid) and Liquid phase transition(means transformation of liquid into solid like water turned into ice..) then which one ...
0
votes
2answers
76 views

Thermodynamics problems with a cycle (insufficient data?)

I am having some troubles in solving the following problem a professor gave us, and in my opinion I think that either there are insufficient data or the solutions are infinite. We have a perfect gas,...
2
votes
2answers
87 views

Information content in black holes

Bekenstein-Hawking formula for entropy of a black hole tells us that information content in a black hole is proportional to its area which is in fact proportional to the mass^2 of the black hole. The ...
0
votes
0answers
11 views

How to compare scales in a thermodynamic system

Suppose we have a generic system with hamiltonian \begin{equation} H= JH_1 +\mu H_2 \end{equation} where $J$ and $\mu$ are couplings and $H_1$ and $H_2$ are just two dimensionless parts of the ...
-1
votes
1answer
48 views

If all spacetime paths inside a black hole point towards the singularity, then does that mean entropy is decreasing?

Entropy is a concept of disorder. A drop of blue ink inside a glass of water only has 10^10 factorial possible ways of being an ink drop, but it has 10^11 factorial possible ways of being an ink soup. ...
0
votes
1answer
22 views

Fastest way heat water (or some other liquid or material)

If I want to heat lets say, 1 liter of water - would it be faster if I heat half a liter, and then another half a liter? or slower? my guess is that its not equal (lets assume that the time it takes ...
0
votes
2answers
19 views

Stress v/s Strain in a heated frustum between 2 rigid walls

So consider a situation where we have a frustum b/w 2 walls. We heat it , so it wants to expand but the walls prevent it from doing so. Does the stress in the frustum remain constant or not Say we ...
1
vote
1answer
76 views

First law of therodynamics appiled across a normal shock

This is a snippet from the book Compressible Flow by Anderson. Here, he is trying to evaluate the change in entropy across the shock using the relation, $s_2 - s_1 = c_p \ ln \frac{T_2}{T_1} - R \ ln ...
0
votes
1answer
22 views

How much energy from air to ice? [closed]

If... "A" is the mass of air (standard air composition and pressure) "I" is the mass of ice "V" is the volume of the box where the change of heat happens (no heat interaction with out of the box) ...
1
vote
3answers
48 views

Blowing smoke out of the clean air - can someone explain?

Yesterday my wife and I were out walking. The weather was cloudy and humid (it had been raining a few hours before). Around 15 C. Suddenly, with no apparent reason, both of us had smoke coming out ...
2
votes
4answers
83 views

Approximation of multiplicity when Ideal gas low density is applied $\frac{M !}{(M-N)!} \approx M^{N}$

Our lecturer today mentioned how a piston's head being at equal pressure maximised the multiplicity of states. He mentioned the following: If I have a fixed number of particles $N_A$ on left and $...
1
vote
2answers
42 views

Using Boltzmann distribution, what is the ratio of probabilities of two states?

I got the probability of state $i$ (in terms of Boltzmann distribution) as $$p_{i}=\frac{1}{Z_{i}}e^{-\epsilon _{i}/{kT}},$$ where $Z_{i}$ is the canonical partition function: $$Z_{i}=\sum_{i}e^{-\...
1
vote
1answer
23 views

Linear expansion over temperature change

From the equation $\Delta L=aL\Delta T$, $\frac{\Delta L}{\Delta T} = aL$ For small change $\frac{dL}{dT}=aL$ Solving we get $L(T)=e^{aT}$ (as differentiating it with respect to temperature gives $...
0
votes
2answers
61 views

Does the ideal gas law apply to a moving vehicle?

If for example you have a car travelling along a road. There is obviously a high pressure region in front of the car, where the air is forced around the vehicle. Likewise, I understand that cars will ...
1
vote
0answers
34 views

If a steam injector increases pressure by lowering temperature would a 'refrigerant injector' work using ambient heat?

In a Giffard type steam injector, boiler feed water is added to the boiler by passing steam at around 10 bar/180C through a converging/diverging nozzle, collecting cold water in the vacuum at the vena ...
1
vote
2answers
48 views

Why a reversible engine's efficiency must be equal to that of a Carnot engine

Apparently, in order to prove that an engine must be as efficient as a Carnot engine if reversible is because apparently for its efficiency in either direction: $\eta_E \le (1-T_2/T_1)$ $\eta_R \ge (...
0
votes
1answer
41 views

Fundamental Energy Equation comparison confusion

I was listening to an introductory lecture today about the fundamental energy equation given below. $$d U=T d S-P d V+\sum_{j=1}^{M} \mu_{j} d N_{j}$$ My lecturer mentioned that through simple ...