Thermodynamics (PHYS2140)
BSc, Physics - PHYS
Semester: First Semester
Level: 200
Year: 2016
REPUBLIC OF CAMEROON
Peace-Work-Fatherland
THE UNIVERSITY OF BAMENDA
P.O BOX 39 Bambili
School/Faculty: Science Department: Physic Lecturer: Mr. HOLTOMO Oliver
Course Code: PHYS2140 Course Title: Thermodynamics
Date: 05/03/2016
Hall: PBA-08
Time:07:30
–
10:30
Instructions: Clarity, concision and Precision will be taken into account
Exercise 1: (17 marks)
1.
Represent the isotherms of perfect gases, real gases and Van der Waals gases in different p-V
diagrams,
2.
State the main differences between them.
3.
Write the van der Waals state equation. Give the conditions of idealizing this state equation.
4.
Determine the critical point p
c
, V
G
, T) of van der Waals gases in terms of constants a, b and R.
Exercise 2: (18 marks)
The state equation of a real gas is written ÷
v = RT, where R = 8.3J/mil.
o
K, a =
41.4Pa.
o
K.m
6
/mol. The molar specific heat at constant volume is given by C
v
=
R whatever the
temperature when the pressure tends to zero.
1.
Write the elementary heat in term of Cv and l coefficients.
2.
Establish the relationships l = T
and
= T
starting by the fact that dU and DS
are total. -
3.
Find the expression of C
v
and 1 at temperature T and molar volume v of the gas.
4.
Calculate the change ∆C
v
, when the molar volume passes from v
0
to 2v
o
at constant temperature vo =
20 I/mol, T = 20°K.
Exercise 3: (10 marks)
The experiments have shown that, the isobaric thermal expansion coefficient and the
isothermal
compression coefficient of 1mol of a gas, is expressed in term of independent variables p and T.
They are written by the equations; =
and =
()
where R and b are constants. Find the equation of state of this gas, relative to one mole.
Exercise 3: (10 marks)
www.schoolfaqs.net
In relation with a source of heat temperature T
A
, a monoatomic gas performs a cyclic process. The cycle
is composed of the adiabatic process (A →B), followed by the isochoric process (B→ C) and end
by the isothermal process (C →A). All these transformations are considered as reversible. The initial state
variables are pA, V
A
and T
A
. After the adiabatic process, V
B
= 2V
A
1) Represent the cycle in the p-V diagram.
2) Express the state variables (p, V, T) at B and C in terms of p
A
, V
A
or T
A
.
3) Find the expressions of heat Q and work W of each process in the cycle in terms of p
A
, V
A
or T
A
.
4) Find the efficiency of the cycle = \W
total
\
5) Deduce the change in internal energy U and in entropy S of each process in the cycle.
www.schoolfaqs.net
