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First Law of Thermodynamics

  • Two objects are in thermal equilibrium if they do not exchange heat when in contact.
  • Zeroth law of thermodynamics: If A and B are in thermal equilibrium with C, then A and B are in thermal equilibrium with each other.
  • First law of thermodynamics: ΔU = Q + W, where ΔU is the change in internal energy of a system, Q is the amount of heat added, and W is the work done ON the system. Q > 0 if heat is added, and Q < 0 if heat is removed.
  • Another version of the first law: ΔU = Q – W, where W is the work done BY the system.
  • If a process undergone by a system is represented on a P-V diagram, then the work by the system in going from the state represented by point A to the state represented by point B is the area under the curve connecting A to B.

First Law of Thermodynamics

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

AP Physics B