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9 months ago in Thermodynamics By Debashis Mohapatra

Can i just add energy and entropy together?

I saw someone write E = F + ST, treating energy as a sum of something spatial and something statistical. Is that a real equation?

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By Emma Answered 2 months ago

It looks like someone tried to reverse-engineer Helmholtz free energy: F = E − TS. Rearranged, E = F + TS. But that's not a general decomposition of energy it's a thermodynamic identity valid only for systems at constant temperature. Energy and entropy have different units, so you can't just add them without temperature (T) converting entropy into energy units. The equation isn't wrong in context, but it's not a universal truth.

 

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