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Wednesday, March 2, 2011


A physics textbook definition of “heat” would be something like “the spontaneous transfer of energy due to a temperature difference”. It is a process, not a state. This is to be made distinct from temperature and internal or thermal energy. I consistently drill the definition of heat into the heads of my students, but I feel that I am fighting an uphill and possibly useless battle for several reasons:

  • The everyday use of the term is usually as a state. defines it as “the condition or quality of being hot.” The terms heat, temperature, and thermal energy are interchangeable in the minds of most students.
  • Engineers and chemists often use the term as both a state and a process. Though they would not equate heat with temperature, I don’t get the sense that the strict physics definition is being reinforced in other classes.
  • Certain terms in physics cause confusion. “Specific heat capacity” is an especially annoying one.

To sum, I see our own field as somewhat muddled and inconsistent, related fields as very inconsistent, and everybody else as completely confused. While we must struggle with definitional inconsistencies all the time (our “velocity” is more specific as it includes a direction and our “acceleration” is more general as is it includes slowing down and changing direction), I find that “heat” is by far the toughest to resolve.

Eugene Hecht has been tackling these issues. He has published letters or articles in The Physics Teacher on problems with the definitions of “energy” and “mass”. I can only hope he’ll read this and set the matter straight.


Asa Maria Bradley said...

I too struggle with getting my students to understand that heat isn’t the same as temperature and that you can talk about transfer of heat even if things are not hot. I’ve been teaching E&M this quarter and had to explain that electromotive force is not a force and that electric potential energy and the electric potential, although very similar phrases are different concepts altogether.

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