Physics I / First Law of Thermodynamics
Practice question · Multiple choice

The first law says ΔU=QW\Delta U = Q - W, and internal energy is a state function while heat and work are not. What does that distinction mean in practice?

Hints
  1. Ask what changes if you go between the same two states by a different route.
  2. Which of the three quantities is fixed by the endpoints alone?
Show the answer

B. That ΔU\Delta U depends on the endpoints and QQ, WW on the path

Why

The split between QQ and WW is a property of the journey; their difference is not. This is exactly what makes engine cycles worth designing.

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