All Questions
Tagged with thermodynamics pressure
786 questions
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Heating object in airless environment
Lets assume I had two containers sitting over a fire or some source of heat. Lets say I also placed two of the same objects with a low melting point in these containers (lets also assume this object ...
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1
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Work in a two-compartment system
A well-insulated container of fixed volume is divided into two equal compartments by a thermally-conductive, weightless, frictionless piston. Initially, compartment A, on the left, contains 50 mol of ...
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2
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115
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Pressure of mixture after mixing [closed]
An insulated rigid tank is divided into two compartments by a partition. One compartment contains $3 \,\text{kmol}$ of $\mathrm{O}_2$, and the other compartment contains $5 \,\text{kmol}$ of $\mathrm{...
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Is the product of pressure and volume of an ideal gas equal to its energy?
While solving a physics problem book (Narayana coaching material Physics for Jee advanced volume 4), I came across this question.
An ideal gas undergoes a process in which $PV^{-a} = \text{constant}$,...
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Which of the following processes (a) isothermal, (b) isobaric, work done will be maximum?
Sir i am facing very difficultly in this following question. It will be so kind of you if you can explain this question to me:
This question is about the thermodynamics from the applications of 1st ...
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In an isobaric system, is the change in internal energy always equal to (3/2) times the work done?
In my high school class, we are learning the basics of thermodynamics. Some of the equations we have learned are $\Delta U = \frac {3}{2}nR\Delta T$ where $\Delta U$ is the change in internal ...
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1
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Why the exhaust pressure should be equal to ambient pressure? (Part 2) [closed]
I'm asking a follow-up question to J. Pipiskin's post: Why the exhaust pressure should be equal to ambient pressure?.
TRF's answer shows a plot of normalized thrust vs exhaust-to-ambient pressure ...
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Why thermodynamic equilibrium and pressure balance is considered for having a reversible process? [duplicate]
When we compare the rapid expansion of an ideal gas to a very slow expansion from an initial state to a final state, we categorize one as irreversible and the other as reversible. This distinction ...
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2
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Is $T(V, P)$ a valid state equation for an ideal gas?
If I consider an ideal gas with constant number of particles, I can easily think an experiment where I can control $(V, T)$ or $(P, T)$ independently (state variables). But I cannot imagine an ...
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Confused about empty plastic bottle in the freezer situation
Note: When I say the bottle is "empty", take it to mean, "with just air inside", as we use in everyday life! :)
My question: Suppose we put an "empty" closed common ...
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Why Gifford-Mcmahon cycle's Refrigeration Effect is $Q=V(P_1-P_2)$?
This extract is from Advances in Cryogenic Engineering (Vol 11). They do give an explanation for my question in Volume 6, but I am struggling to understand that
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Considerations for phase change through throttle valve
I am looking at characterizing, as well as I can, the exit velocity and density downstream of an isenthalpic throttle valve as a function of the downstream pressure. What is throwing me off is the ...
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2
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Help me to understand why we have $pV$ in the enthalpy equation
I'm learning (slowly) about enthalpy. My understanding is that enthalpy is the sum of internal energy and the work done on the environment, in order to occupy a volume $V$ at pressure $p$?
$$H = U + ...
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What happens to entropy during compression?
I learnt that entropy in the universe can only be created, never destroyed. (And so change in entropy can never be negative, right?)
But during compression, don't we increase the order in, say, the ...
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Is it possible to lower the temperature of a gas by pressurizing it to an extreme degree?
If we look at temperature as a measure of the kinetic energy present in moving gas molecules, could we lower a gas's temperature by making it impossible for the molecules to move by pressurizing it to ...
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Does a cube under high pressure transform into a ball?
Will a material in the shape of a cube, under high pressure, crumble into the shape of a ball?
One would expect that there will develop strains and stresses, after which the corners crumble and ...
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Why do the hydrogen-based jet engines create propulsion?
Theoretically, the jet engines create propulsion because of the pressure in the combustion chamber that creates force that pushes the rocket.
But when hydrogen combustion is conducted, 2 hydrogen ...
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Brilliant's question on air pressure
I have always thought that as temperature increases the pressure does as well in an ideal gas, of course I know the air in the atmosphere isn't exactly an ideal gas but I would've thought that the ...
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Name of Pressure for real gas
Actually I was reading through the book, when I noticed this plot.
I am curious how all those isotherms pass through the same point, which leads me to wonder if there is a pressure for which the ...
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3
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Does the Gas do Work When I remove the barrier? [duplicate]
Let's suppose I have 2 boxes, one with gas molecules in. The other without.
I then magically remove the barrier connecting the two gasses. The pressure inside the box and volume taken up by the gas ...
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Calculating correction term for Non-constant Temperature situations in Relation between Height and Air pressure [closed]
Background
We initially have $$p(h+\Delta)-p(h)=-g\rho(\xi)\Delta$$ as of the definition of pressure, where $p(h)$ is the pressure at height $h$, $\rho(h)$ is the air density at height $h$.
By taking ...
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Proportionality of Pressure and Temperature in defining Absolute Temperature scale
I am studying thermodynamics and came across this kind of loop:
First, an absolute temperature scale is attempted to be defined as follows
Assume that temperature is proportional to the pressure of ...
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6
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Why is pressure in the outermost layer of a star lower than at its center?
I have done the math and I have obtained the hydrostatic pressure in a star is lower at the outermost layer of a star than in its center, where the pressure is actually maximum. Although the equations ...
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Contribution of rotational mode in ideal gas law
The ideal gas law is very accurate for an $N_2$ gas when the temperature is around 300K and the pressure is around 1atm. At these conditions, $N_2$'s compressibility factor is 0.997, which means that ...
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Clarifying the definition of pressure in statistical physics
I am studying David Tong's lecture note on statistical physics, and I have a question regarding the precise definition of pressure. I checked other postings in this community, but was unable to get ...
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Work done by gas and it's limits
So I have read about how when pressurised gas does work, it decreases in temperature (turbo expanders, Claude liquefaction etc.). How exactly does that work? The more work a gas does, the more it ...
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When we pour cold water on a closed jar containing only hot water and water vapour, why does the hot water in jar start boiling?
Here is a video link for the experiment.
In the experiment, cold water is being poured on a closed jar containing hot water and water vapour and we observe that the hot water inside jar starts boiling....
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Pressure difference between a box and the outside atmosphere
Say I have a box of volume $V$, with an ideal gas inside it with temperature $T_b$. I don't know the number of particles inside it. The box is surrounded by the room's environment, which has ...
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Will compressing a gas but keeping the temperature constant allow me to compress it further without significant resistance?
Let‘s say we compress a cylinder with gas. If I make sure to cool the cylinder to keep it at ambient temperature, will the force needed to compress the air also stay constant? If not, how much will it ...
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Cohesion forces and evaporation due to pressure reduction
So, we all know that there are two ways to evaporate a liquid, either by increasing its temperature through heating, which could be explained microscopically, as we're providing the molecules of the ...
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5
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Why $VdP$ term omitted in isothermal Work?
Context: I'm asking about classical thermodynamics, that is "ideal gas", closed system, reversible processes etc.
Why is the $VdP$ term omitted in calculation of work during isothermal ...
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How much pressure would it take to compress a block of solid steel into one-tenth the original volume?
We all know to compress objects into smaller volumes, you would need to apply pressure to them. The required pressure depends on how strong the material is and which form is it (gas, liquid, solid).
I ...
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2
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85
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What is the pressure immediately after compression of air?
Rearranging the gas law equation to Pressure = nRT/V shows that a reduction in volume by 10 should yield a 10x increase in pressure.
But compressing air also causes a rise in temperature. Immediately ...
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2
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What regulates the size of our atmosphere?
Our atmosphere is only about 100km thick before the official start of space. That is a mere 1.57307% of the radius of Earth (6,357km). The difference between the gratitational force at sea level and ...
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Definition of the pressure in statistical mechanics
I just had a glimpse of Feynman's statistical mechanics. On page 8, I saw a 'third' definition of pressure:
$$ P = - \frac{\partial U }{\partial V} (V, S) . $$
I am curious why it is $S$ but not $T$. ...
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Entropy of mixing via partial pressures
I was deriving the equations for calculating the entropy change $\Delta S_M$ of the system where ideal gases are being mixed.
The first one utilizes partial pressures via Dalton's law:
$$\Delta S_M= \...
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1
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Does tea cool down faster at altitude than at sea level; is the rate of cooling faster?
I've found this question impossible to find online because all the answers talk about the boiling points and freezing points at different altitudes.
The question is whether the rate of cooling or ...
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How to explain the phenomenon of air bag, when have one object hit air bag and one object catapult from air bag
Problem of this phenomenon is in title.To describe this, I separate it into 3 phases;
M1 hit airbag, 2) Air moving inside air bag caused by pressure gradient ,
3)M2 flew away caused by air moving to ...
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2
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Why is the work done by an expanding ideal gas $\textbf{P}_{ext}\Delta V$?
Consider an ideal gas in a cubical container as our system (only the gas is the system, not the walls of the container). If I understand correctly, if the gas expands at constant pressure $P_{int}$ ...
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Confusion about finding enthalpy change
I have a confusion about something in the following question.
An ideal diesel engine has a compression ratio of
20 and uses air as the working fluid. The state of air at the beginning of the ...
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2
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84
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Do negative pressures in Thermodynamics lead to a negative stress energy tensor?
If we have a gas or liquid described by the van der Waals gas law with negative pressure, does that lead to a negative stress energy tensor?
Does a stretched liquid for example have a negative stress ...
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Why is an adiabat steeper than an isotherm in a $p$-$V$ curve?
What I have so far gathered is a mathematical explanation.
Since for an adiabatic process, $pV^γ=$ constant, for a unit change in pressure, change in volume would be very less. Therefore, if compared ...
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How is entropy calculated in a Constant Temperature process, when a gas is compressed from from $p_1$ to $p_2$? [closed]
Entropy for constant temperature process, when instead of volumes, pressures changes from $p_1$ to $p_2$?
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1
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Does Andrews curve's density in Liquid- Saturated vapor phase change region vary or not?
Are Andrews Curve (isotherms) for gas-liq phase change less dense for low values temperature and more dense for high value of temperature?
I came up with this because of Clausius Clapeyron Equation ...
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1
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How do I convert weight of compressed, liquid $\rm CO_2$ in canister to cubic meters at atmospheric pressure?
I need compressed $\rm CO_2$ for a project I'm working on, and am trying to figure out how much volume of gaseous $\rm CO_2$ I get from a given weight of liquid $\rm CO_2$ in canister. As far as I can ...
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Is this a simple proof that gas pressure is a relativistic invariant?
This is a simple thought experiment that hopefully demonstrates that gas pressure is an invariant in relativity.
Consider two very long sealed rectangular boxes that contain equal gas pressure when at ...
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Does air gap between enclosed chamber and manometer influence the manometer reading?
We have an enclosed chamber filled with water. From the top of the chamber there is a metallic tube connecting the chamber to a monometer. We increase the pressure of the water inside the chamber buy ...
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Fuel Cell Operating Pressure
I have seen anecdotal testing of fuel cell stacks. Intended to demonstrate that their power output can be improved through the addition of a centrifugal blower.
What are the limits associated with ...
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3
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What is the liquifaction pressure for hydrogen?
According to the most reliable source on the internet. Hydrogen has a density of 0.07099 Kg/L. Thus divided by it's molecular mass, in one liter of liquid hydrogen we should have 35.21888395 mol.
...
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Atmosphere of a hypothetical planet
A hypothetical planet is 2/3 the radius of earth but has 1g surface gravity. Given the planet has the same surface gravity as earth, the atmospheric pressure would be the same. This would also mean ...
