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Does anyone know the word for this? Physics must have a word for how energy in forms such as electricity can do work, but once transformed into thermal energy
by CookieMon 11y ago
Does anyone know the word for this?
Physics must have a word for how energy in forms such as electricity can do work, but once transformed into thermal energy it can no longer do work (a temperature difference is required to perform work, and then only at carnot efficiency — a temperature alone cannot perform work).
I asked on reddit once, and someone suggested "exergy" but I think that word is explicitly concerned with heat, so couldn't be used to say things like "1000w of electricty provides more exergy than 1000w of gas", or "An electric space heater destroys the exergy of the electricity it consumes, while a computer uses it for computation".
So is there a word?
- kozak 11y agoLet me quote "Mysteries of Modern Physics: Time": "Energy is conserved, but it can change forms. If you have energy in a low-entropy form, you can do useful work with it. You can lift something up, drive a car, or fly an airplane. If you convert that energy into a high-entropy form, it becomes useless. A low-entropy concentration of energy is called fuel. We have fossil fuels sitting in the ground with energy in them in a concentrated form. We can extract the energy because the entropy of the fuel is low. Once we burn the fuel, we cannot go back. You can heat a room in your house by burning wood, but you cannot cool off a room in your house by unburning fuel and turning it into wood."
- FiatLuxDave 11y agoExergy is the best word, actually. Another equivalent term is energy quality. Your example sentences are completely correct.