Physics 7B, Fall 2007, Section 2, Instructor: Prof. Adrian Lee
Final Examination, Monday December 17, 2007
Please do work on these pages.
You can use the backs and extra paper is supplied.
You
may use three double-sided 3.5” x 5” index card of notes and a calculator.
Test duration
is 3 hours.
Please be explicit in your derivations, show your work, and box your
answers!
Name __________________________
Disc. Section ____________________
SID ___________________________
#1______ (40)
#2______ (20)
#3______ (30)
#4______ (30)
#5______ (40)
Total______ of 160

This
** preview**
has intentionally

**sections.**

*blurred***to view the full version.**

*Sign up*
1.
(
Giancoli, 20.66
) A real heat engine working between heat reservoirs at
T
L
= 400K
and
T
H
= 850K produces
W
= 600J of work per cycle for a heat input of
Q
in
= 1600J.
The
heat output is labeled
Q
out
.
In all subparts, please write your answer in terms of variables
before putting in numbers.
(
40 pts
)
a) What is the efficiency of this real engine? If the engine were a Carnot engine
operating between the same two heat baths, what would the efficiency be?
You can use
the efficiency formula for a Carnot engine. (
10 pts
)
b) Calculate the total entropy change of the universe for each cycle of the real engine.
(
10 pts
)
c) Calculate the total entropy change of the universe for a Carnot engine operating
between the same two temperatures. Do not simply assert the answer, but provide a
proof. (
10 pts
)
d)

This is the end of the preview.
Sign up
to
access the rest of the document.