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Can we compare alive cells with heat engines at all? No, not really, because the living being isn't only a heat engine. There are three main points I want to make here. 1. Homeostasis Requires Constant Energy Input This statement is especially true and obvious of homeotherms Mammals (Mammaliaformes, descended from the Therapsid Synapsid Amniotes), and ...

8

Why is the efficiency of human cells less than efficiency of an Otto engine? It's not. You are comparing two very different things. The low value of 18 to 26% efficiency you found for the human body is the energy produced by an exercising human compared to the energy consumed by that person. The high value of 56 to 61% efficiency is for an ideal Otto cycle ...

4

The most immediate answer would seem to be that a great variety of different crystal phases can exist because their long-range order makes it possible to classify them based on the different symmetries of their lattice structure. Since the liquid (or amorphous solid) phase only has short-range order and the gaseous phase doesn't even have that, it seems ...

3

P-V work is not the only kind of work that can be done on the contents of your system. In the case of your fan example, the fan is doing work on the gas within the container by exerting force on it through a displacement (of the fan blade). The kinetic energy imparted to the gas by the fan is then converted to internal energy by viscous dissipation (a ...

3

In statistical mechanics, the most important behavior of a system (and the starting point for any more detailed analysis) is the bulk behavior in the limit where its size is macroscopic (i.e. $N\sim 10^{23}$). Statistical mechanical predictions of macroscopic thermodynamic properties (like total energy and entropy) can be decomposed into distinct sectors ...

1

Thermodynamics was developed largely with gases in mind. In this case work can be done on the gas, the $p\Delta V$ term. But there is also the internal energy U to consider, so when one wants to compare experiments done on the same substance under different conditions it is useful to define a new quantity, which is the enthalpy, as the internal energy plus ...

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