- #1
Hari_Seldon
- 3
- 0
Hello,
I am a Math student trying to learn some Thermodynamics and Statistical Mechanics on my own. This has been quite hard, because many concepts are confusing and the terminology is a mess. I have zero background in Physics, so forgive my complete ignorance.
My main problem at the moment is with the definition of heat. From what I understand, the word heat is used with two different meanings. The first meaning is: heat is a kind of energy transfer, as is work, but heat and work are different (and I cannot really understand the difference).
The second meaning is that heat is an amount of energy contained in a system. Correct me if I am mistaken: the sum of all energy contained in a system is called "internal energy"; it may be divided in a potential energy part and a kinetic energy part; this kinetic energy part, also called "thermal energy", corresponds exactly to the second meaning of heat.
In summary the first meaning corresponds to a flow of energy and the second, which should be replaced by "thermal energy", corresponds to a stock of energy. This is somewhat confusing but from the context, it is usually easy to understand which of the two meanings is being employed.
However, I have found the following in my http://www.google.com/url?sa=t&sour...521Bw&usg=AFQjCNFxzInRHyxwpoz2JR4f9yBdaeAJLg"
The principle qualitative difference between work and heat is very simply explained in the microscopic picture. According to that picture, heat is energy which is statistically distributed over all particles. For instance, let us consider some particles with parallel (ordered) momenta which move in one direction. The kinetic energy of these particles can be completely regained at any moment and can be converted into other forms of energy, e.g., by decelerating the particles through a force. However, if the particles move in a completely disorder and statistical manner, it is obviously not possible to extract all the kinetic energy by a simple device. (...) It is therefore considerably simpler to change work into heat, which practically always happenx by itself than to gain utilizable work from heat.
Now, this confuses me completely. I cannot say in which of the two meanings "heat" is being used above, or if it is actually in a third, new meaning I don't know of. Heat is being compared to work, which suggests that it should be understood as an energy transfer, but at the same time I see the idea of something contained in the system that we are trying to extract.
I know I haven't really asked any precise question, but maybe someone can see the source of my confusion and tell me something that clarifies my mind. If so, I would be really thankful.
I am a Math student trying to learn some Thermodynamics and Statistical Mechanics on my own. This has been quite hard, because many concepts are confusing and the terminology is a mess. I have zero background in Physics, so forgive my complete ignorance.
My main problem at the moment is with the definition of heat. From what I understand, the word heat is used with two different meanings. The first meaning is: heat is a kind of energy transfer, as is work, but heat and work are different (and I cannot really understand the difference).
The second meaning is that heat is an amount of energy contained in a system. Correct me if I am mistaken: the sum of all energy contained in a system is called "internal energy"; it may be divided in a potential energy part and a kinetic energy part; this kinetic energy part, also called "thermal energy", corresponds exactly to the second meaning of heat.
In summary the first meaning corresponds to a flow of energy and the second, which should be replaced by "thermal energy", corresponds to a stock of energy. This is somewhat confusing but from the context, it is usually easy to understand which of the two meanings is being employed.
However, I have found the following in my http://www.google.com/url?sa=t&sour...521Bw&usg=AFQjCNFxzInRHyxwpoz2JR4f9yBdaeAJLg"
The principle qualitative difference between work and heat is very simply explained in the microscopic picture. According to that picture, heat is energy which is statistically distributed over all particles. For instance, let us consider some particles with parallel (ordered) momenta which move in one direction. The kinetic energy of these particles can be completely regained at any moment and can be converted into other forms of energy, e.g., by decelerating the particles through a force. However, if the particles move in a completely disorder and statistical manner, it is obviously not possible to extract all the kinetic energy by a simple device. (...) It is therefore considerably simpler to change work into heat, which practically always happenx by itself than to gain utilizable work from heat.
Now, this confuses me completely. I cannot say in which of the two meanings "heat" is being used above, or if it is actually in a third, new meaning I don't know of. Heat is being compared to work, which suggests that it should be understood as an energy transfer, but at the same time I see the idea of something contained in the system that we are trying to extract.
I know I haven't really asked any precise question, but maybe someone can see the source of my confusion and tell me something that clarifies my mind. If so, I would be really thankful.
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