Thermodynamics unit test
A test on this unit alone, marked as a percentage and a letter grade — for the test your class is actually sitting, rather than for May. Answer everything, then submit once: seeing the answer to question 3 before attempting question 4 makes the final percentage meaningless.
Isobaric
Temperature is not heat
Second law of thermodynamics
Coefficient of performance
Reading engine versus refrigerator off a PV loop
Temperature vs thermal energy
Why a PV cycle's enclosed area is net work
PV diagram work
Ideal gas law
Isothermal, isobaric, isochoric, adiabatic
Ideal gas process on a PV diagram
Latent heat
Short answer 1. Define or explain: Kelvin is not optional
3 ptsShort answer 2. Define or explain: Adiabatic
3 ptsShort answer 3. Define or explain: Isochoric
3 ptsShort answer 4. Define or explain: What internal energy depends on
3 ptsFree response
12 ptsTRANSLATION BETWEEN REPRESENTATIONS (Question 2, 12 points). A sample of monatomic ideal gas is sealed in a thermally conducting container by a movable piston of mass M and area A. The container sits in a large water bath held at constant temperature T0. The piston moves with negligible friction. At the instant shown, the gas is in thermal equilibrium with the bath, the piston is at rest, and the gas occupies volume V0. The pressure of the air above the piston is Patm. For C: a block, also of mass M, is placed on the piston at t = t0 and slowly lowered; the piston comes to rest at t = tf when the block is fully released. For D: with the block still on the piston, the bath is changed to a new constant temperature Tnew, and at the new equilibrium the gas again occupies V0.
A. Describe the free-body diagram of the piston: each force exerted on it, with direction, as distinct labeled arrows from a dot.
B. Derive an expression for the internal energy of the gas in terms of M, A, V0, Patm, and physical constants, as appropriate. Begin with a fundamental physics principle or an equation from the reference information.
C. Describe the pressure-versus-volume curve for the process the gas undergoes from t0 to tf, including the direction of the process arrow.
D. Indicate whether Tnew is greater than, less than, or equal to T0, and briefly justify by referencing at least one feature of your answers to parts A, B, or C.