تم الحل ✓
categoryالفيزياء
schoolبكالوريوس
event_available2026-07-15
السؤال
Transcribed Image Text:
2) From the lecture (compare also text page 193-194) we learn that the maximum amount
of work which can be extracted from a system interacting with a single heat reservoir is
given by Wx=-AF where AF = F, -F, is the change of the Helmholtz free energy
of the system.
Specifically for water at initial temperature To and constant heat capacity Cp interacting
with a heat reservoir at temperature TR this maximum amount of work reads
Wx=-AF=C(T-TR)+CT In(T/TO).
Perform now an explicit calculation to confirm the
above expression. Let a Carnot cycle run between the
water and the reservoir (see sketch). The Carnot
engine is small taking in only infinitesimal small
amounts of heat per cycle. The water of constant heat
capacity Cp is initially at temperature To. The
reservoir is at constant temperature TR. The Carnot
cycle runs until equilibrium is reached (hint: take into
account that the temperature of the reservoir initially
at To is changing and thus the changes the Carnot
efficiency continuously).
Calculate the total amount of work produced by the
Carnot cycle. Express your result in terms of To, TR
and Cp and compare with W from above.
max
To-To(t) with
lim T₁(t) = T
1-
Carnot
TR=const
W
(5points)
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