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I was thinking about it and in a sense heat is an interesting quantity that can only be created and not destroyed. In comparison with the first law this means that ultimately for a closed system all internal energy will be converted into heat. Does this make any sense? How would you write this in continuity equation form?

$$ \frac{d\rho}{dt} + \nabla \cdot\vec{\jmath} = \sigma, $$ where $$ \sigma \geq 0.$$

Would a good analogy be that in comparison with charges, imagine if all charge is conserved, and charge can only be destroyed and not created (so the inverse for heat). This means that the total net charge will stay the same but the total different charge (or potential) will go down in time. Then there would be a 'second law' for charge it seems because ultimately any system would end up with only as neutral as possible charge.

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  • $\begingroup$ You need to define the symbols in your equation. $\endgroup$
    – Bob D
    May 11, 2022 at 20:05
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    $\begingroup$ The conflation of entropy, thermal energy, and the process of heating can lead to confusion. You've used "heat" to refer to all three in this question. It is entropy that can't be destroyed. It is thermal energy that is a type of energy. It is the process of heating that transfers energy as driven by a temperature difference. They are not identical; thus, the premise of the question is—in my opinion—invalid. $\endgroup$ May 11, 2022 at 20:15
  • $\begingroup$ Chemomechanics is correct. You are confusing so many concepts that it is impossible to formulate a coherent response, other than to encourage you to take a basic course in thermodynamics. $\endgroup$
    – Bob D
    May 11, 2022 at 20:53
  • $\begingroup$ @Chemomechanics thank you for pointing out all the concepts I was confusing $\endgroup$ May 12, 2022 at 8:53

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In comparison with the first law this means that ultimately for a closed system all internal energy will be converted into heat. In comparison with the first law this means that ultimately for a closed system all internal energy will be converted into heat. Does this make any sense?.

No. A system does not "contain" or "store" heat. Heat is energy transfer between a system and its surroundings due solely to temperature difference.

How would you write this in continuity equation form?

$$ \frac{d\rho}{dt} + \nabla \cdot\vec{\jmath} = \sigma, $$ where $$ > \sigma \geq 0.$$

Since you have not defined the terms in your equation, I can't comment on it.

Would a good analogy be that in comparison with charges, imagine if all charge is conserved, and charge can only be destroyed and not created (so the inverse for heat).

No it would not be a good analogy. Heat is not a "conserved" quantity like charge.

Then there would be a 'second law' for charge it seems because ultimately any system would end up with only as neutral as possible charge.

Sorry, I have no idea what you are talking about.

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  • $\begingroup$ Why the downvote? (I know it is useless asking, because downvotes never need to be justified). $\endgroup$
    – Bob D
    May 12, 2022 at 1:08

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