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Death eater
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What is difference between perfect gas and ideal gas?
I want to know about it used in engineeringDrClaude said:There is a difference between usage in physics and in engineering. While physicists often use both terms interchangeably, this is not the case for engineers.@Chestermiller can fill in the details better than me.
Yes, that's correct. And I considered not including #3, but, for a neophyte to thermodynamics, I felt it would helpful to include.Lord Jestocost said:For a gas whose equation of state is exactly given by ##pV = nRT##, the specific internal energy depends only on temperature. Thus, if definition (1.) holds, definition (3.) is redundant.
We're still waiting for a Physicist to respond with their version of an ideal gas and perfect gas. We engineers use ideal gas and perfect gas interchangeably. Anyway, you said you were more interested in the engineering definition (which I gave).Death eater said:I haven't got the difference between ideal gas and perfect gas?
You have given the characterstics of ideal gas, they are true but I needed how can we differentiate between ideal and perfect gas?Chestermiller said:We're still waiting for a Physicist to respond with their version of an ideal gas and perfect gas. We engineers use ideal gas and perfect gas interchangeably. Anyway, you said you were more interested in the engineering definition (which I gave).
Like I said, I'll leave it up to Physicists to provide their version of things. You have our answer from us engineers.Death eater said:You have given the characterstics of ideal gas, they are true but I needed how can we differentiate between ideal and perfect gas?
I know one of the difference, it is that in ideal gases specific heat vary with temperature but in perfect gas specific heat is constant. I wanted to know more about it.
vanhees71 said:Indeed, at least in my community (relativistic heavy-ion physics, which uses relativistic statistical physics, including transport theory, thermal QFT, hydrodynamics, as one of its most important tools), there's no difference made between a "perfect" and an "ideal" gas. In fact, the expression "perfect gas" is never used.
From point of view of kinetic theory, one can define an ideal gas as a gas whose consituent particles have a mean free path which is much shorter than the typical space-time scales upon which the macroscopic properties of the gas changes. This implies equilibration (or relaxation) times much shorther than the typical timescales for changes of the macroscopic properties. Then the motion of the gas can be described well with ideal hydrodynamics, which implies that the gas is, on the resolution of macroscopic space-time scales, always in local thermal equilibrium.
Yikes. This is the same as what we engineers assume.vanhees71 said:Indeed, at least in my community (relativistic heavy-ion physics, which uses relativistic statistical physics, including transport theory, thermal QFT, hydrodynamics, as one of its most important tools), there's no difference made between a "perfect" and an "ideal" gas. In fact, the expression "perfect gas" is never used.
From point of view of kinetic theory, one can define an ideal gas as a gas whose consituent particles have a mean free path which is much shorter than the typical space-time scales upon which the macroscopic properties of the gas changes. This implies equilibration (or relaxation) times much shorther than the typical timescales for changes of the macroscopic properties. Then the motion of the gas can be described well with ideal hydrodynamics, which implies that the gas is, on the resolution of macroscopic space-time scales, always in local thermal equilibrium.
According to the author your book, he defines a perfect gas as an ideal gas with constant heat capacity.Death eater said:View attachment 231708
I am confused after reading. I don't know what it is trying to say.
Now I am more confused. What is perfect gas?Chestermiller said:According to the author your book, he defines a perfect gas as an ideal gas with constant heat capacity.
I don't know how I can say this more precisely. Sorry. My advise is to not obsess over the difference, and to continue on with your learning.Death eater said:Now I am more confused. What is perfect gas?
Ok, thanks any way for your tineChestermiller said:I don't know how I can say this more precisely. Sorry. My advise is to not obsess over the difference, and to continue on with your learning.
Death eater said:Now I am more confused. What is perfect gas?
A perfect gas is a hypothetical gas that follows the ideal gas law under all conditions of pressure and temperature. It has the following characteristics: it is composed of point masses with no volume, there are no intermolecular forces between the particles, and collisions between particles are perfectly elastic.
An ideal gas is a simplified model of a real gas that assumes the particles have negligible volume and there are no intermolecular forces between them. This means that in an ideal gas, the particles do not interact with each other, whereas in a perfect gas, the particles interact but their interactions are perfectly elastic.
The ideal gas law is a mathematical equation that describes the relationship between the pressure, volume, temperature, and number of moles of an ideal gas. It is written as PV = nRT, where P is pressure, V is volume, n is the number of moles, R is the gas constant, and T is temperature.
No, a real gas cannot behave exactly like a perfect gas because it does not meet all the assumptions of a perfect gas. Real gases have non-zero volumes and intermolecular forces, which can affect their behavior under certain conditions of pressure and temperature.
The ideal gas law is only accurate under certain conditions, such as low pressures and high temperatures. It also assumes that the particles do not interact with each other, which is not always the case for real gases. Additionally, it does not take into account the volume of the gas particles, which can become significant at high pressures.