They are all assumed to be 100% accurate so there isn't one that is "most accurate".
"Unavailable for doing work" is related to the Second Law of Thermodynamics.
Second Law of Thermodynamics
The Second Law of Thermodynamics.
Thermodynamics is both a law and a theory. It has a set of well-established laws, such as the first and second laws of thermodynamics, which describe the behavior of energy in systems. Additionally, the principles and concepts underlying thermodynamics are formulated into a theory to explain and predict the behavior of physical systems.
the internal energy (thermal energy)
Not exactly. The first law of thermodynamics, i.e. the law of conservation of energy, also accounts for heat as one of the many forms that energy can take. There is no one law called "the law of thermodynamics", but there are several "Laws of Thermodynamics" (note the plural form "LAWS").
There were several mathematical ideas which interacted with thermodynamics. By far the most important of these is statistics.Some physicists believe that the Second Law of Thermodynamics is the one physical law of whose validity we can be totally certain, because it is based on statistics.
Thermodynamic cycle is based on 2nd law of thermodynamics.
Magic
The 1st Law of thermodynamics is a restatement of the law of conservation of energy.
The first law of thermodynamics is also known as the Law of Energy Conservation.
"Unavailable for doing work" is related to the Second Law of Thermodynamics.
Entropy is closely related to the 2nd law of thermodynamics, not the 1st law. The 1st law of thermodynamics states that energy cannot be created or destroyed, only transferred or converted. Entropy, on the other hand, is a measure of the disorder or randomness of a system, which increases over time according to the 2nd law of thermodynamics.
That law is known as the Law of Conservation of Energy. It is also known as the First Law of Thermodynamics.
The first law of thermodynamics states that energy cannot be created or destroyed in an isolated system; it can only change forms. This law is also known as the Law of Conservation of Energy.
There is no commonly accepted law by that name, as far as I know. Two important laws about energy are the First Law of Thermodynamics and the Second Law of Thermodynamics.
That's related to the First Law of Thermodynamics - the Law of Conservation of Energy.