# Tagged Questions

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

40 views

### Estimate heating wires temperature

Im design a power supply to work with heating wires and one of the task is to estimate the temperature of the bare wire for a given current or power consumption. I've tried to measure the ...
38 views

### Inversion and Isenthalpic Curves for van der Waals EOS

When I plot the isenthalpic curves in P-T plane, I see Joule-Thomson coefficient is positive in the lower inversion curve but it must be negative. Some authors consider the minimum inversion ...
85 views

### Evaporation of water

Consider a cylinder that there is water inside it. The volume (and so the pressure) of the cylinder is adjustable by a piston. The thickness of the cylinder and piston is very negligible. The cylinder ...
26 views

### Statiscal treatment of multiparticle system (Thermodynamics) [closed]

If a system of two energy levels with energies $\epsilon_1$ and $\epsilon_2$ is populated N particles at temperature T. The degeneracy of both levels is one. The particles populate the microstates to ...
50 views

### Can a High Enough Temperature Create a Black Hole?

My very basic understanding of GR leads me to think that if a substance has a high enough temperature, it can transform into a black hole without a mass required to create a black hole. The equation ...
46 views

### How can removing energy from a system do work? (ice)

Water freezing into ice expands, damaging roads, breaking rocks, etc. To my understanding, this is doing work (in a physics sense) by removing energy from the system. How is this possible?
36 views

### how to calculate enthalpy and internal energy in relation to heat capacities?

I remember that $\mathrm du=c\mathrm dT$ and $\mathrm dh=c\mathrm dT$ with $c$ being two different heat capacities, but I can't find anything about it, any help?
39 views

### Thermodynamics: efficiency of a heat engine [closed]

How can we calculate efficiency of a real heat engine? Do we have to consider volume of an object while calculating efficiency? Like in this question If so, how we have to proceed? Thanks in ...
31 views

### specific volume in a saturated steam mixture

In saturation temperature, we have both gas and liquid. In the steam tables, I don't know if the liquid is in form of droplets inside the steam or in the form of normal liquid water at the bottom of ...
10 views

### Acoustic energy

Let's Assume that I'm sitting in a hypothetical container(room) whose 6 walls are PERFECTLY AND IDEALLY rigid and also are PERFECTLY reflective. Now if I start speaking anything in this room and so ...
132 views

### Does entropy always increase with temperature? [duplicate]

For any system can we always say that entropy increases with temperature. In other words: $$\left(\frac{\partial S}{\partial T} \right)_{\{\alpha\}}\ge0$$ where $\{\alpha\}$ is the set of parameters ...
133 views

### Obtaining the temperature from Bose-Einstein and Fermi-Dirac distribution

Lets say you are given a distribution function $f(p)$ and you want to define a temperature, $T_f$, for this distribution. (I assume $\mu = 0$.) It is then natural to define a temperature the ...
49 views

### Clausius Inequality with three reservoirs

Deriving Clausius inequality in the case of two reservoirs is quite simple. We assume that there is a thermal machine operating between two reservoirs, the first at temperature $T_1$ and the second at ...
64 views

### 2 times the velocity, 4 times the energy, 8 times the heat

In SpaceX's webcast today they talked about the first stage getting back to Earth with twice the velocity as usual. I quote: "So 4 times as much energy means harder on the stage, and 8 times as much ...
98 views

### How do ceiling fans cool or heat?

Why does a ceiling fan blowing air downward cool in the summertime: whereas a ceiling fan sucking air upwards heats in the wintertime: ? Why isn't it the other way around?
36 views

### How do I find the temperature of an object being heated on one side and cooled on the other [closed]

Ok so i'm trying to figure out what temperature a beam would be when one end is put into the ground and the other side is in the open air above. Assuming the beam is perfectly insulated besides the ...
83 views

### Intuition about the cosmological significance of the chemical potential

A definition of the chemical potential that has always served me well is $$\mu_i = \Big(\frac{\partial U}{\partial N_i}\Big)_{S,V},$$ that is, the amount of energy one would have to add to a system ...
21 views

### Liquid Temperature Profile

Suppose I have a one meter cubed box of liquid and I know that it is in a $-4^\circ~\rm C$ room for some amount of time, but was at a uniform $25^\circ ~\rm C$ when it was placed inside. I know I can ...
37 views

### Why does increasing heat conductivity decrease Nusselt number?

Normally we expect that when heat conductivity(k) increases heat transfer is also increases. But for fluids increasing k decreases Nusselt number. My senses tell that using high conductive fluid cause ...
35 views

54 views

### Maximum temperature possible on earth

What is maximum temperature that can we have on earth on a single day? Lets say an air mass is static over an area and there is no way for air mass to move, sun warming it up would increase ...