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Entropy in a thermally isolated system

In page 141 of the book "Concepts in thermal physics" it is said that for a thermally isolated, the change in entropy is bigger or equal to 0 since $dQ=0$. But since the system is thermally ...
AankNum's user avatar
  • 11
1 vote
1 answer
108 views

What is the relationship between Clausius Inequality and 2nd Law?

I am confused about the application of the 2nd Law for reversible and irreversible processes and cycles. I want to know how the Clausius principle, the Kelvin-Planck statement, and the Clausius ...
Skaeler's user avatar
  • 31
4 votes
3 answers
1k views

Difference between spontaneous and irreversible process?

I am confused about the difference between a spontaneous process and an irreversible process. Based on what I read so far, both processes increase universe's entropy. I never heard of any reversible ...
John Davies's user avatar
6 votes
3 answers
840 views

Example of an irreversible process using this formal definition

Some time ago, I asked for a definition of thermodynamic reversibility without mentioning entropy, and a user came up with the following formal definition of a reversible process: Definition: ...
armoredchihuahua's user avatar
1 vote
3 answers
183 views

A reversible transformation, but there is finite temperature heat transfer?

Suppose to have 3 heat reservoirs, the first at temperature $T_1$, the second at temperature $T_1+dT$ and the third at temperature $T_2>T_1$ Then, consider a system, which volume is constant, in ...
SimoBartz's user avatar
  • 1,978
2 votes
1 answer
48 views

Equivalence of various definitions of reversibility in classical mechanics

I was reading Classical Mechanics: The Theoretical Minimum by Leonard Susskind, and the definition of reversibility in that was: Given a state of a system, then we know exactly what state it came ...
Neeladri Reddy's user avatar
2 votes
2 answers
97 views

Defining reversibility without resorting to entropy

Is it possible to define the concept of reversible process without using any mention to entropy? The Wikipedia definition of reversible process seems to accomplish this by stating that: In ...
armoredchihuahua's user avatar
1 vote
1 answer
169 views

Contradiction in definition of entropy?

I'm studying for my thermodynamics exam and I came across something which really confuses me. An infinitesimal change in entropy $ dS_{sys}$ of a system at temperature $T_{sys}$ during a reversible ...
Dabruh's user avatar
  • 146
2 votes
3 answers
432 views

On the way adiabatic processes were defined in Blundell's Concepts in Thermal Physics

In Blundell's Concepts in Thermal Physics, page $117$, the author defines an adiabatic expansion as follows, The word adiathermal means ‘without flow of heat’. A system bounded by adiathermal walls ...
Hilbert's user avatar
  • 1,292
1 vote
1 answer
112 views

Question reg. reasoning of deterministic reversible cyclical laws - The Theoretical Minimum

I recently started reading "The Theoretical Minimum: What you need to know to start doing Physics". In the first chapter, the authors define the "Minus-First law", and state that reversible ".. laws ...
skittish's user avatar
  • 143
0 votes
4 answers
4k views

What is quasi-static process?

What is the formal definition of quasi static process? I am accustomed with it a bit intuitively, i want to know the formal definition of this. At some source I found the definition of somewhat ...
Bijayan Ray's user avatar
5 votes
2 answers
894 views

The actual definition of entropy

According to the inequality of Clausius, $$S\ge \dfrac {q_{rev}}T$$ , where $S$ is the entropy of the system, $q$ the heat absorbed by the system during a reversible process and $T$ is the ...
Archer's user avatar
  • 375
3 votes
1 answer
1k views

Entropy for irreversible processes

According to the mathematical definition of entropy, it is only defined for reversible processes only. Then how can it be defined for irreversible processes? Please explain clearly.
Ronak Nahata's user avatar
4 votes
1 answer
140 views

Reversible process, equivalence of two definitions?

There are two common definitions of a reversible process: A reversible processes is quasistatic with no dissipation. And A process where an infinitesimal change in conditions would reverse the ...
Quantum spaghettification's user avatar
2 votes
1 answer
700 views

Definition of Entropy for reversible and irreversible process

$\int \dfrac{\delta Q}{T}$ can't be used to calculate entropy of an irreversible process. If you happen to know heat supplied and temperature at which it is supplied for just an instant. Can you then ...
user31058's user avatar
  • 1,471
7 votes
5 answers
1k views

Definition of entropy in thermodynamics

In most textbooks, the definition of entropy in reversible processes on a system $S$ is given simply as $$d S=\delta Q/T.$$ It seems to me this definition is insufficient since it does not specify ...
user16397's user avatar
  • 171