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What is Energy in Thermodynamics ?

  1. Jul 24, 2011 #1
    Using Thermodynamics we can measure a certain quantity that is preserved/transferred during a process and we call it energy.
    We feel it's existence based on it's effect on other observable quantities(say motion for instance) and we do not "know" energy as itself.Am I right?

    So do we energy only as a cause and never as itself?
  2. jcsd
  3. Jul 24, 2011 #2
    i think we can define it like that under some lmitations
    Last edited by a moderator: Jul 25, 2011
  4. Jul 24, 2011 #3
    Your first statement is pretty much saying that energy is intangible, which is true.

    However, I don't understand the above. Can you please clarify?
  5. Jul 24, 2011 #4
    I am really sorry.
    I meant to say,"Do we feel energy only as a cause and never as itself?".

    Let's say,we feel the effect of heat energy,temperature,we don't feel heat energy itself now,do we?
  6. Jul 24, 2011 #5
    Not a correct assumption.

    When we feel the effect of heat energy, energy is still intangible. No matter how much we want to, it will never become tangible as you seem to suggest so it's impossible to say something like "heat energy itself".

    If we do feel the effect of heat energy, well, then we feel the effect of heat energy.

    I think that, itself, would be a reasonable analysis. This, rather, is due to the fact is because energy is intangible. You cannot pick up 5J of energy here and there.

    If there is something extra that I don't understand, can you please clarify? Thanks.
    Last edited: Jul 24, 2011
  7. Jul 24, 2011 #6


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    Staff: Mentor

    No. Making observations and connecting them to each other with math is what physics is about. So that's all that energy is!
  8. Jul 24, 2011 #7
    Thank you Aravind,Hubewa and Russ.
    You have given me more insight not only to my question but also to the presentation of a question.
    So the bottom line is energy is an inherent entity in the universe and it's presence is ascertained only by it's effect on measurable parameters.
  9. Jul 24, 2011 #8


    Staff: Mentor

    Before you go too far you may want to read other threads by the same name:


    These have both been within the last couple of months, both threads were locked, and both resulted in the ban of one or more of the participants. By going through the existing threads you can probably find the information you need without risking getting banned yourself.
  10. Jul 24, 2011 #9
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