Thermodynamics Law

A Thermodynamics Law is a physical laws that governs thermodynamic systems.

• Example(s)
  • Zero Law of Thermodynamics.
  • First Law of Thermodynamics.
  • Second Law of Thermodynamics.
  • Third Law of Thermodynamics.
• Counter-Example(s)
  • Newton's Laws of Motion.
  • Ideal Gas Law.
• See: Entropy, Temperature, Heat, Work, Pressure, Heat Engine.

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References

2016

• (Wikipedia, 2016) ⇒ https://www.wikiwand.com/en/Laws_of_thermodynamics
  • The four laws of thermodynamics define fundamental physical quantities (temperature, energy, and entropy) that characterize thermodynamic systems. The laws describe how these quantities behave under various circumstances, and forbid certain phenomena (such as perpetual motion).

The four laws of thermodynamics are:

• Zeroth law of thermodynamics: If two systems are in thermal equilibrium independently with a third system, they must be in thermal equilibrium with each other. This law helps define the notion of temperature.
• First law of thermodynamics: When energy passes, as work, as heat, or with matter, into or out from a system, its internal energy changes in accord with the law of conservation of energy. Equivalently, perpetual motion machines of the first kind are impossible.
• Second law of thermodynamics: In a natural thermodynamic process, the sum of the entropies of the interacting thermodynamic systems increases. Equivalently, perpetual motion machines of the second kind are impossible.
• Third law of thermodynamics: 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, and is equal to the logarithm of the multiplicity of the quantum ground states.

There have been suggestions of additional laws, but none of them achieves the generality of the four accepted laws, and they are not mentioned in standard textbooks.

The laws of thermodynamics are important fundamental laws in physics and they are applicable in other natural sciences.

1963

• (Feynman et al., 1963) ⇒ Richard P. Feynman, Robert B. Leighton and Matthew Sands (1963, 1977, 2006, 2010, 2013) "The Feynman Lectures on Physics": New Millennium Edition is now available online by the California Institute of Technology, Michael A. Gottlieb, and Rudolf Pfeiffer ⇒ http://www.feynmanlectures.caltech.edu/
  • Chapter 44: Summary of the laws of thermodynamics

First law: Heat put into a system + Work done on a system= Increase in internal energy of the system:

[math]\displaystyle{ dQ+dW=dU }[/math]

Second law:A process whose only net result is to take heat from a reservoir and convert it to work is impossible. No heat engine taking heat [math]\displaystyle{ Q_1 }[/math] from [math]\displaystyle{ T1 }[/math] and delivering heat [math]\displaystyle{ Q2 }[/math] at [math]\displaystyle{ T2 }[/math] can do more work than a reversible engine, for which

[math]\displaystyle{ W=Q1−Q2=Q1(\frac{T1−T2}{T1}) }[/math]

The entropy of a system is defined this way:

(a) If heat [math]\displaystyle{ \Delta Q }[/math] is added reversibly to a system at temperature T, the increase in entropy of the system is [math]\displaystyle{ \Delta S= \Delta Q/T }[/math]

(b) At T=0, S=0 (third law).

In a reversible change, the total entropy of all parts of the system (including reservoirs) does not change. In irreversible change, the total entropy of the system always increases.

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