I wish to understand the reversible and irreversible processes in thermodynamics.
I understand that A thermodynamic process is reversible if the process can return back in such a that both the system and the surroundings return to their original states, with no other change anywhere else in the universe. It means both system and surroundings are returned to their initial states at the end of the reverse process.
My question is following:
Is it necessary that every slow process with no dissipative forces into it, will be necessarily reversible?
I mean, how do we judge whether a given process is reversible or not? "Slow" and "Absence of dissipative forces" are the only two and exhaustive conditions?
This is something of an ideal since if the system was in equilibrium it wouldn't be changing at all, so in practice a reversible process is one in which the system is very close to equilibrium throughout the process.
By slow, I understand we generally mean quasi-static or always equilibrium condition.
So, if the following two conditions are met, then can we say that the process will be necessarily reversible? 1. Quasi-static. 2. Absence of dissipative forces in the system.
Sir, Can we say that the fundamental reason for the above definitions is, the Second Law of Thermodynamics. If the gas's internal energy converts even a bit into kinetic energy of the piston, then there is no way it can be given back to gas, so it will become an irreversible process.
And piston will gain some kinetic energy if the equilibrium condition is not met, so the process must be quasi-static.
I think the fundamental reason is that a system takes time to adjust to changes. For example consider an ideal gas. In thermodynamics we consider this as a continuous system but in reality it is a collection of gas molecules moving at a finite velocity.
If you make some change to the system that change cannot propagate through the system faster than a gas molecule can move, so the finite speed of the gas molecules sets a limit on how fast the system can react to changes.
When we talk about a slow process we mean the process happens slowly enough that the gas can react fast enough to stay in equilibrium (or near to it) all the time.
@DevanshMittal As you know, if I target 6 month for preparation for JEE 2021 to get atleast under 1000 rank, so, taking physics in account, the most basic idea would be to split 11th and 12th Syllabus and complete each one of them, one by one.
That'd be almost 5 days for one chapter in Physics.
Are such splits good idea?
because some chapters take a lot of time to cover and some doesn't take more than a day to get over...
That's what I actually do, but revision schedule is worth? Because I'm not sure, after 6 months, I'll be able to recall all those which I've read today...
I've been thrown in the penalty box because I allegedly made rude comments and I had to cool down. What happens if one is thrown in the box for a second (or third, fourth...) time? Will he/she (or I) get extra punishment on top?
Is there a limit on the number of times you can be put in there?
Not...
I've been thrown in the penalty box because I allegedly made rude comments and I had to cool down. What happens if one is thrown in the box for a second (or third, fourth...) time? Will he/she (or I) get extra punishment on top?
Is there a limit on the number of times you can be put in there?
Not...
Like, my professor has asked me to research and write about a subject I don't know anything about. So in this case I feel I should provide a refernce for every sentence I write (after paraphrasing/summarizing ofc)
Not really. If you quote a chunk of text verbatim, put the reference at the end of the quote. If you're paraphrasing one or several articles, put the references to the articles at the end of the paraphrase
If the entire section is a paraphrase, it's also common to say something like "In the following, we recount the results of [1], [2] and [3]" and then not mention the references again in that section.
What's important is that the reader can clearly tell what part (if any) is your own original work. If the entire thing is clearly a review of extant literature that's of course not a real concern.
Is time something special in QM? Can it be treated just like position or momentum? the energy-time uncertainty (with the defn used) gives the same factor of $\frac{\hbar}{2}$ so maybe there is some connection with other observables?
look at joshphysics' answer to the question I linked - the $\Delta t$ has nothing to do with a time operator.
@Yashas That's commonly known as "Pauli's theorem" - if time were an operator, it should be one with fully continuous spectrum like position and momentum, but since it would also have to be conjugate to the Hamiltonian, the Hamiltonian would have to be, too, but energy is always bounded from below and usually at least partly discrete in realistic systems since there is a ground state.
@Archer if it's like textbook-level well-known it's okay to omit the reference or just give one at random, but for research-level things it's usually expected that you cite the original paper - that's how certain papers get thousands of citations: They did something that was fundamental to a subfield and then basically every paper in that subfield cites them in their introduction.
@Stupidquestioninc Imagine you only had one of the masses, say A, there. In that picture they're calculating the force F on the mass C in the direction of the point O. Since the attractive force from A points in the direction of A, the force F is the component of this attractive force in the direction of O, which is $F_{CO}=F_{CA}\cos\alpha$.
