Timeline for Why can we get maximum work from a reversible process?
Current License: CC BY-SA 4.0
11 events
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| Nov 26, 2020 at 18:59 | comment | added | Bob D | @Dale Agree, especially the convention for work which depends on which version of the first law you use. For one version, W is positive if done by the system and negative if done on the system. For the second version (more commonly used in chemistry) its the reverse.. At least for heat it's consistent. | |
| Nov 26, 2020 at 16:38 | comment | added | Dale | @BobD you are absolutely right, that is the purpose. I don’t know why the thermodynamic sign conventions are the way they are. To me they are the most confusing sign conventions of any major branch of physics | |
| Nov 26, 2020 at 15:31 | comment | added | Bob D | I missed the statement "The work done on a heat engine". Sorry about that. My comment was based on the thinking that the purpose of a heat engine is to do work, not to have work done on it. | |
| Nov 26, 2020 at 15:24 | comment | added | Dale | @BobD yes, so $Q_h$ is a negative quantity and the work done on the engine is negative. The thermo sign conventions are very confusing. | |
| Nov 26, 2020 at 14:33 | comment | added | Bob D | "where $Q_c$ is the heat entering the cold reservoir and $Q_h$ is the heat entering the hot reservoir." For a heat engine, doesn't heat exit to the cold reservoir and enter from the hot reservoir? | |
| Nov 26, 2020 at 13:14 | history | edited | Dale | CC BY-SA 4.0 |
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| Nov 26, 2020 at 13:12 | comment | added | Dale | @Ankit Sorry about that. I added the explanation of $Q_h$ and $Q_c$ into the answer. Entropy doesn’t take away energy, but it limits how much heat can be converted to work. It limits that because work has 0 entropy and the second law of thermo requires that entropy never decrease. So the entropy of the heat must increase by at least a minimum amount as given above. | |
| Nov 26, 2020 at 12:58 | history | edited | Dale | CC BY-SA 4.0 |
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| Nov 26, 2020 at 12:49 | comment | added | Ankit | what is $Q_c$ and $Q_h$ here ? Also why and how does entropy take away some energy ? | |
| Nov 26, 2020 at 12:29 | history | edited | Dale | CC BY-SA 4.0 |
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| Nov 26, 2020 at 12:10 | history | answered | Dale | CC BY-SA 4.0 |