Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Marika on 03/08/2018 10:03:55
-
Aditi wants to know:
If potential energy increases with height, does hot air gain energy when it rises? And in turn, does its temperature continue to increase because of the energy?
What do you think?
-
Temperature is a form of kinetic energy (largely), and therefore we would expect a mass of warm air to cool as it rises, as the kinetic energy of its temperature gets exchanged for potential energy of its height (and this is typically what is observed).
-
If the air just rose, and did nothing else, it would maintain exactly the same temperature. If it expanded, which it often does, then it would cool.
But conservation of energy applies, air rising will dissipate energy in the form of air friction both ahead and behind it, so the air around it will get slightly hotter, but not necessarily much heat will end up in the air itself. In some cases it can also do electrical work and generate lightning.
-
Really nice question; I'd never actually thought about this. Thanks for the answers too everyone!
-
Temperature is a form of kinetic energy (largely), and therefore we would expect a mass of warm air to cool as it rises, as the kinetic energy of its temperature gets exchanged for potential energy of its height (and this is typically what is observed).
Excellent response. My compliments to the chef!
-
Careful here. Is the gas not expanding adiabatically?
-
I think you're right wolfe keeper. It seems that temperature is defined through the mean of the total number of molecules, not caring whether 'this parcel of air' expands, or not. Pressure though, is related to kinetic energy, as molecules bumping into each other. But as a 'parcel' expands there will be less bumping and less pressure keeping the kinetic energy at a level plane.