Unit 5 Thermodynamics

5.1 Exercises

OpenStax

Section 5.1 Exercises

  1. During a thermodynamic process, a system moves from state A to state B, it is supplied with 400 J of heat and does 100 J of work.
    (a) For this transition, what is the system’s change in internal energy?
    (b) If the system then moves from state B back to state A, what is its change in

    internal energy?
    (c) If in moving from A to B along a different path, 400 J of work is done on the system, how much heat does the system absorb?
    (Question adapted from LibreTexts: https://phys.libretexts.org/Bookshelves/University_Physics/Book%3A_University_Physics_(OpenStax)/Book%3A_University_Physics_II_-_Thermodynamics_Electricity_and_Magnetism_(OpenStax)/03%3A_The_First_Law_of_Thermodynamics/3.04%3A_First_Law_of_Thermodynamics)
  2. If 5 J are taken away by heat from the system, and the system does 5 J of work, what is the change in internal energy of the system? (Question from OpenStax Physics)
  3. How much work is done by a gas under 20 Pa of pressure increasing in volume by 3.0 m3? (Question from OpenStax Physics)
  4. Explain pressure-volume work. (Question from OpenStax Physics)

Solutions

  1. (a) +300 J; (b) −300 J; (c) −100 J
  2. −10 J
  3. −60 J
  4. It is the work that is done by the compression or expansion of a fluid.

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