 |
TPH601S - THERMAL PHYSICS - 2ND OPP - JULY 2022 |
|
|
1 Page 1 |
▲back to top |
&
NAMIBIA UNIVERSITY
OF SCIENCE AND TECHNOLOGY
FACULTY OF HEALTH, APPLIED SCIENCES AND NATURAL RESOURCES
DEPARTMENT OF NATURAL AND APPLIED SCIENCES
QUALIFICATION: BACHELOR OF SCIENCE
QUALIFICATION CODE: 07BOSC
LEVEL: 6
COURSE CODE: TPH601S
COURSE NAME: THERMAL PHYSICS
SESSION: JULY 2022
PAPER: THEORY
DURATION: 3 HOURS
MARKS: 100
SUPPLEMENTARY/SECOND OPPORTUNITY EXAMINATION PAPER
EXAMINER(S) | MR. VAINO INDONGO
MODERATOR: | DR. SYLVANUS ONJEFU
INSTRUCTIONS
Write all your answers in the answer booklet provided.
2.
Read the whole question before answering.
Begin each question on a new page.
PERMISSIBLE MATERIALS
Non-programmable Scientific Calculator
THIS EXAMINATION QUESTION PAPER CONSISTS OF 3 PAGES
(INCLUDING THIS FRONT PAGE)
Page 1 of 3
|
|
2 Page 2 |
▲back to top |
QUESTION 1
[30]
1.1 Briefly explain the following thermodynamic terms:
(10)
(a) Surrounding
(b) Open system
(c) Heat
(d) Thermal equilibrium
(e) An isolated system
1.2 Ona brisk autumn day (3.0°C) the tires of a car were inflated to a pressure of
2.80 x 10° Pa. The tire gauge reads 1.4 x 10° Pa, but this is the excess above
atmospheric pressure, which is about 1.01 x 105 Pa. Assuming that the tires and
air inside are in equilibrium with the outside air, what is the Kelvin temperature of
the air inside?
(2)
1.3 A copper strip is 50.0 mm long at 0°C. How long would it be at 150°C if the coefficient
of linear expansion for Brass is 1.7 x 10° °C +?
(3)
1.4 (a) Estimate the amount of heat needed to raise the temperature of 50.0 g of lead
(c = 1.28x107 J.kg+ K+) from 2.3 °C to 196.0 °C.
(3)
(b) At 16.0°C, a brass cube has an edge length of 30.0 cm. What is the increase in
the cube’s volume when it is heated to 81.0°C? The coefficient of linear expansion
for brass is given by a = 19.00 x 10° °C?.
(5)
1.5 A2.00 g sample of methanol (cm = 2450 J.kg+ K+) at 20°C is mixed with 1.00 g of water
(cw = 4180 J.kg* K*) at 60°C. The system is insulated and attains its equilibrium
temperature Teg.
a) Using the definition of specific heat, set up the Qtotal = 0 equation.
(3)
b) Calculate the final temperature 7; of the mixture.
(4)
QUESTION 2
[24]
2.1 State the 2" Law of thermodynamics and write its differential form.
(5)
2.2 What is isochoric (isometric) process? If 1265 J of heat energy is expelled from a gas
confined in an isochoric process, evaluate the change in internal energy of the gas.
(4)
2.2 State the molar specific heats of an ideal gas and discuss how these molar specific
heats are related. Also, write down the ratio y in terms of these specific heats.
(4)
2.4 An ideal gas undergoes an isothermal expansion at temperature T, changing its
volume from V; to V;. Use an ideal gas law to show that the work done during an
Page 2 of 3
|
|
3 Page 3 |
▲back to top |
isothermal expansion is given by the equation:
W = nRTin (4)
(6)
2.5 Draw and label correctly a P-V diagram of three isotherms of temperatures T1 = 200 K,
T2 = 260 K and T3 = 230 K. Illustrate an adiabatic curve on the same diagram, cutting
through all isotherms.
(5)
QUESTION 3
[31]
3.1 The efficiency of a particular car engine is 20% when the engine does 8.5 kJ of work
per cycle. Assume the process is reversible. Calculate
(a) The energy the engine gains per cycle as heat Qgain from the fuel combustion?
(3)
(b) The energy the engine loses per cycle as heat Qhost.
(3)
(c) If a tune-up increases the efficiency to 32%, recalculate the
(i) Qgain.
(3)
(ii) Quost-
(3)
3.2 Draw and explain the states of the Carnot Cycle (on a p-V diagram) including the
work done per cycle, temperature, heat transfer.
(12)
3.3 Determine the entropy of 1500 g of water vapor at 125°C (Specific heat capacity of
ice =2090 J.kg*K?, water 4200 J.kg* K+, water vapor steam = 1996 J.kg? K+, latent heat
of fusion of water = 3.33x10° J.kg? and vaporization is 2260 J.kg7*).
(7)
QUESTION 4
[15]
4.1 Prove that py’= constant for adiabatic process
(8)
4.2 Derive thermodynamic Maxwell equation based on Gibb’s Free Energy.
(7)
END OF EXAMINATION!
Page 3 of 3