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The question is, what distinguishes thermal energy from kinetic energy?
What distinguishes thermal radiation from other electromagnetic radiation?
Quote from: hamdani yusuf on 19/03/2022 03:56:58The question is, what distinguishes thermal energy from kinetic energy?The motion having some sort of structure, rather than being random. Essentially, it's an effect of entropy.Quote from: hamdani yusuf on 19/03/2022 03:56:58What distinguishes thermal radiation from other electromagnetic radiation?In the case of your experiment, the spectrum.
For there to be an exchange of heat, the mean internal kinetic energy of one object must decrease and that of the other object must increase. We measure mean kinetic energy as temperature. If two objects are at the same temperature, their temperatures will not change by putting them in contact with one another. That's how temperature is derived from the zeroth law.
What seems more relevant is just to jump straight to a higher level answer:"Temperature", "thermal contact" and "heat" are all very difficult things to define. At least, they are difficult to define or explain at any microscopic scale (where you're trying to take a reductionist approach and break things down to the smallest indivisible units like particles with well defined properties). However, they can be easily defined (or really just decalred to exist) on a macroscopic scale. This is the usual development of the subject matter that is called "thermodynamics".
Do you have any idea why it's hard to define?
For example, if you try to take a microscopic definition for "heat" then it is not supposed to include a transfer of matter from one system to another BUT a transfer of photons such as infra-red radiation is something we would very much like to include in the definition of heat. What makes a photon different to some other particle with energy? If an electron and positron cross a barrier then that would seem to be a transfer of matter across the barrier and would not be considered as a heat transfer. However, if they annhilate on one side of the barrier, only some photons cross the barrier and then the photons interact with some nucleus on the other side of the barrier to reform particles and anti-particles - that would seem to be just fine.
Quote from: hamdani yusuf on 29/03/2022 08:30:31Do you have any idea why it's hard to define?As he said; there's a difference between the macroscopic and microscopic pictures.You also need to be aware of thishttps://en.wikipedia.org/wiki/Equipartition_theoremAnd thishttps://en.wikipedia.org/wiki/Virial_theorem
https://en.wikipedia.org/wiki/Equipartition_theoremIn classical statistical mechanics, the equipartition theorem relates the temperature of a system to its average energies. The equipartition theorem is also known as the law of equipartition, equipartition of energy, or simply equipartition. The original idea of equipartition was that, in thermal equilibrium, energy is shared equally among all of its various forms; for example, the average kinetic energy per degree of freedom in translational motion of a molecule should equal that in rotational motion.
Quickly rotating magnets or electrets in a box have large kinetic energy,
Quote from: hamdani yusuf on 29/03/2022 04:14:47Quickly rotating magnets or electrets in a box have large kinetic energy,You ignored the word "internal" in my quote. It isn't there for padding!
Temperature is a statistic of a very large ensemble so it is only defined macroscopically.
Quote from: alancalverd on 29/03/2022 11:02:19Temperature is a statistic of a very large ensemble so it is only defined macroscopically.How many molecules is the minimum limit for a system to have a defined temperature?
seems
For large molecules, it seems to be easier to vibrate than translate or rotate,
What makes it (temperature) easier to define in macroscopic picture?
Is there any exclusion from following methods of heating water?- Radio wave heating- Microwave heating- Infrared heating- Visible Laser heating- Induction heating- Ohmic heating
Different systems can have different state variables. Temperature and Pressure are just some common examples of state variables that some systems have and the ideal gas equation PV = kT is a good example of an equation of state that might apply.
There are some objects and some systems that do not have a well defined temperature. Simple examples: A small container of gas that has been left for days can be assumed to have a well defined temperature. A container of gas that has just had some high velocity gas particles added to one side of it does not have a well defined temperature until enough time has passed and an equilibrium and equi-partition of energy has been established.
I think this ideal gas definition is the simplest way (mathematically) to describe temperature.
Hi.Quote from: hamdani yusuf on 30/03/2022 14:50:42I think this ideal gas definition is the simplest way (mathematically) to describe temperature. Yes. I like a bit of theory. In fairness, we should mention that it's a bit of shame that not everything is an ideal gas. People will still assign a temperature to these things and you can be pretty sure they will have used a hybrid of methods or approaches to defining temperature.Best Wishes.