- #1
DanAbnormal
- 23
- 0
Homework Statement
A reversible heat engine operates between two reservoirs having temperatures T1 and T2 (T2 > T1). The temperature T1 of the cold reservoir remains constant, whereas the warmer reservoir consists of n moles of a gas at constant volume with specific heat capacity Cv. After the heat engine has operated for period of time [tex]\Delta[/tex]t, the temperature T2 has dropped to T1.
i) How much heat is extracted from the warmer reservoir during [tex]\Delta[/tex]t?
ii) What is the change of entropy of the warmer reservoir during [tex]\Delta[/tex]t?
iii) How much work did the engine produce during [tex]\Delta[/tex]t?
iv) What is the change in entropy of the universe during [tex]\Delta[/tex]t?
Homework Equations
Q = nCv[tex]\Delta[/tex]T
The Attempt at a Solution
i) Right for the first part I am assuming [tex]\Delta[/tex]T corresponds to (T2 - T1), so the heat extracted is
Q = nCv(T2 - T1) ?
ii) For the next bit I am not sure. It says the heat engine is reversable, which makes me think there's no change in entropy, however it hasnt completed a cycle in [tex]\Delta[/tex]t. So that can't be right... can it?
iii) For the work done W = Qh - Qc
and Qh (if my attempt at part one is right) is = nCv[tex]\Delta[/tex]T
so W = (nCv[tex]\Delta[/tex]T) - Qc ?
iv) And the last part is kind of the same problem I have with part two.
So for the bits I've done am I right, and for the entropy parts is it zero or not?