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Entropy
Entropy
A thermodynamic quantity representing the unavailability of a system's thermal energy for conversion into mechanical work, often interpreted as the degree of disorder or randomness in the system
A thermodynamic quantity representing the unavailability of a system's thermal energy for conversion into mechanical work, often interpreted as the degree of disorder or randomness in the system
In a natural thermodynamic process, the sum of the entropies (∑S ≥ 0) of the interacting thermodynamic systems increases. Equivalently, perpetual motion machines of the second kind (machines that spontaneously convert thermal energy into mechanical work) are impossible
In a natural thermodynamic process, the sum of the entropies (∑S ≥ 0) of the interacting thermodynamic systems increases. Equivalently, perpetual motion machines of the second kind (machines that spontaneously convert thermal energy into mechanical work) are impossible
If the first law of thermodynamics says you can't win, then the second law of thermodynamics says you can't even break even.
If the first law of thermodynamics says you can't win, then the second law of thermodynamics says you can't even break even.
There are four basic statements that help explain the concept of entropy.
There are four basic statements that help explain the concept of entropy.
Statement 1: Clausius statement
Statement 1: Clausius statement
Clausius statement: Heat will not flow spontaneously from a cold object to a hot object.
Clausius statement: Heat will not flow spontaneously from a cold object to a hot object.
Statement 2:
Statement 2:
Any system which is free of external influences becomes more disordered with time. This disorder can be expressed in terms of the quantity called entropy.
Any system which is free of external influences becomes more disordered with time. This disorder can be expressed in terms of the quantity called entropy.
Statement 3:
Statement 3:
You cannot create a heat engine which extracts heat and converts it all to useful work (you can’t win).
You cannot create a heat engine which extracts heat and converts it all to useful work (you can’t win).
The efficiency (𝜼) of a heat engine is based on work done. (COP for heaters & coolers)
The efficiency (𝜼) of a heat engine is based on work done. (COP for heaters & coolers)
Carnot efficiency (maximum efficiency) is based on temperature. (2nd law 100% work not possible -
Carnot efficiency (maximum efficiency) is based on temperature. (2nd law 100% work not possible -
Not only can't you win, you can’t even break even)
Not only can't you win, you can’t even break even)
Statement 4:
Statement 4:
There is a thermal bottleneck which constrains devices which convert stored energy to heat and then use the heat to accomplish work. For a given mechanical efficiency of the devices, a machine which includes the conversion to heat as one of the steps will be inherently less efficient than one which is purely mechanical.
There is a thermal bottleneck which constrains devices which convert stored energy to heat and then use the heat to accomplish work. For a given mechanical efficiency of the devices, a machine which includes the conversion to heat as one of the steps will be inherently less efficient than one which is purely mechanical.
The Carnot cycle sets the ideal efficiency which can be obtained if there is no friction, mechanical losses, leakage, etc., but real machine efficiencies are much less.
The Carnot cycle sets the ideal efficiency which can be obtained if there is no friction, mechanical losses, leakage, etc., but real machine efficiencies are much less.
The entropy of a system approaches a constant value as the temperature approaches absolute zero. With the exception of non-crystalline solids (glasses) the entropy of a system at absolute zero is typically close to zero.
The entropy of a system approaches a constant value as the temperature approaches absolute zero. With the exception of non-crystalline solids (glasses) the entropy of a system at absolute zero is typically close to zero.
Entropy Confusion - Sixty Symbols
Entropy Confusion - Sixty Symbols
Entropy is not disorder: micro-state vs macro-state
Entropy is not disorder: micro-state vs macro-state
Entropy and the difference between micro-states and macro-states
Entropy and the difference between micro-states and macro-states
TED-Ed: What is entropy?
TED-Ed: What is entropy?
There’s a concept that’s crucial to chemistry and physics. It helps explain why physical processes go one way and not the other: why ice melts, why cream spreads in coffee, why air leaks out of a punctured tire. It’s entropy, and it’s notoriously difficult to wrap our heads around.
There’s a concept that’s crucial to chemistry and physics. It helps explain why physical processes go one way and not the other: why ice melts, why cream spreads in coffee, why air leaks out of a punctured tire. It’s entropy, and it’s notoriously difficult to wrap our heads around.
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