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5:51 AM
@JohnRennie hi
sorry yesterday I had a class so i could not ask the question which I supposed to ask
 
@JackRod Hi :-)
 
are u available?
 
Yes
 
sir what is microstates and macrostates in
thermodynamics statstical system
 
To be honest I never understood statistical mechanics well as I didn't like it and never put the required effort into it.
So I'm not the person to ask about stat mech :-(
 
5:58 AM
@JohnRennie can u go through this link once
 
OK I've read that.
 
does there explanation for microstate is correct?
 
As far as I can tell it looks fine.
 
but there is one problem I feel
 
As I recall, a microstate is the detailed information about a particular configuration of the system i.e. you need to know the positions and velocities of every particle in your system.
A macrostate is an average of many microstates, and the averaging loses the detailed information that you get in a microstate.
 
6:07 AM
How do I fit the statistical average of the entropy over each microstate into his explanation?
 
No idea ...
 
@JohnRennie did I told u that we are going back to college?
 
Cool :-)
A few of the students have told me that colleges are reopeneing soon. I don't remember if you had told me.
Finally! Life is getting back to normal.
 
but sir they are not opening for regular classes
just lab that is it
and back to home after lab
 
Ah, OK, so they are only opening for the stuff that cannot be done online like practical classes.
 
6:15 AM
yes
for that I need to travel 300km daily
means 600km daily
 
That seems like a bit of a pain. You'll be spending a long time on trains :-(
 
I did not opt for hostel
 
I must admit I would probably have stayed in the hostel.
 
because of some issue but now i feel i should have choosen it
 
Is it still possible to get a hostel place, or maybe some other accomodation?
 
6:17 AM
looking for some rent house near college for a month
or pain guest
type
@JohnRennie can u help in understanding this
It is not that the energy of a system is smeared or spread out over a greater number of microstates that it is more dispersed. That can't occur because all the energy of the macrostate is always in only one microstate at one instant. The macrostate's energy is more "spread out" when there are larger numbers of microstates for a system because at any instant all the energy that is in one microstate can be in any one of the now-
larger total of microstates, a greatly increased number of choices, far less chance of being “localized” — i.e., just being able to jump around from one to only a dozen other microstates or'only' a few millions or so! More possibilities mean more chances for the system to be in one of MANY more different microstates — that is what is meant by "the system's total energy can be more dispersed or spread out”: more choices/chances.
 
I think what it's saying is that the system is only ever in one microstate at a time.
 
ok
 
But it switches rapidly between different microstates e.g. in an ideal gas the microstate changed every time two gas molecules collide, which happens a huge number of times a second.
So when we are talking about averaging microstates we mean a time average i.e. if we average over a time that is long compared to the time between collisions we get a macrostate.
 
sir why measure these things on fix temprature?
 
I'm not sure what you are asking ...
 
6:26 AM
actually in the last line they claculated number of microstates for ice
at fixed temprature
 
I guess fixed temperature means fixed total internal energy.
 
ok
 
So they are including only microstates that have a certain energy.
 
one more thing I want to ask separate from this what is lagrange multiplier?
 
A Lagrange multiplier is a way of doing calculations in classical mechanics.
I must admit I don't remember the details. It's the sort of thing I look up when i need it then forget again.
You'll find info about it in any advanced book on classical mechanics.
 
 
2 hours later…
8:19 AM
@JohnRennie sir in isothermal process entropy change is zero?
if I consider a ideal gas
 
When we consider entropy change it's important to distinguish between the entropy of the system and the total entropy change of the system and its environment.
For example suppose we consider isothermal and reversible expansion of an ideal gas. We have to transfer heat Δq from the environment to the gas in order to keep its temperature constant, so the entropy of the gas increases by ΔS = Δq/T while the entropy of the environment decreases by ΔS = -Δq/T. Yes?
 
yes
 
So the entropy of the gas changes, and the entropy of the environment changes.
But when we add together these two changes to get the total we find the total change is zero.
 
yes
 
But just being isothermal does not mean a change is reversible. For example a Joule expansion is isothermal but it is not reversible so the total entropy change (of the system + the environment) is greater than zero.
 
8:28 AM
what I was thinking I relate entropy with internal energy
 
There are various equations that relate entropy and internal energy, but I have long since forgotten them.
 
yes sir
If i tell about system change in its entropy is constant
 
Assuming we are talking about a reversible change then constant entropy means ∫dq/T = 0
And dU = dq + dW so we get ∫(dU - dW)/T = 0
You could probably work that into some useful equation.
 
 
2 hours later…
10:55 AM
@JackRod Hi :-)
 
sir maxwell thermodynamical equation?
 
The Maxwell-Boltzmann distribution you mean?
 
yes
@JohnRennie
 
OK, what do you want to ask about it?
 
do u have time derive them?
I just want a understanding based derivation
@JohnRennie
 
11:08 AM
I have no idea how it's derived I'm afraid.
I probably learned it at university but I have long since forgotten it.
 
no issue sir
 

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