GENERAL
ENGINEERING
Thermodynamics
Test
Solution Booklet
Instructions
This General Engineering Test comprises of 30 Thermodynamics questions, and
you will have 40 minutes in which to correctly answer as many as you can.
You will have to work quickly and accurately to perform well in this test. If you
don't know the answer to a question, leave it and come back to it if you have time.
You may click Back and Next during the test to review or skip questions.
You can submit your test at any time. If the time limit is up before you click
submit the test will automatically be submitted with the answers you have
selected. It is recommended to keep working until the time limit is up.
Try to find a time and place where you will not be interrupted during the test.
When you are ready, begin the test.
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SOLUTIONS
1.
For the same compression ratio, the efficiency of dual combustion cycle is
A. greater than Diesel cycle and less than Otto cycle
B. less than Diesel cycle and greater than Otto cycle
C. greater than Diesel cycle
D. less than Diesel cycle
Answer: Option A
Explanation:
For Same compression ratios:
Efficiency of Otto cycle is greater than that of Diesel cycle and efficiency of Dual cycle is in-
between Otto and Diesel cycles.
2.
In an irreversible process, there is a
A. loss of heat
B. no loss of heat
C. gain of heat
D. no gain of heat
Answer: Option A
Explanation:
Irreversible process. An irreversible process is one in which heat is transferred through a
finite temperature. Examples:-
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Relative motion with friction.
3.
The amount of heat required to raise the temperature of unit mass of a gas through one
degree at constant pressure is called specific heat at constant pressure.
A. True B. False
Answer: Option A
Explanation:
True
4.
The change of entropy, when heat is removed from the gas, is negative.
A. Yes B. No
Answer: Option A
Explanation:
Change in entropy must be negative if temperature is removed and vice versa.
5.
Coke is produced
A. when coal is first dried and then crushed to a fine powder by pulverizing machine
from the finely ground coal by moulding under pressure with or without a binding
B.
material
when coal is strongly heated continuously for 42 to 48 hours in the absence of air in a
C.
closed vessel
D. by heating wood with a limited supply of air to a temperature not less than 280°C
Answer: Option C
Explanation:
when coal is strongly heated continuously for 42 to 48 hours in the absence of air in a closed
vessel
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6.
One Joule (J) is equal to
A. 1 N-m
B. 1 kN-m
C. 10 N-m/s
D. 10 kN-m/s
Answer: Option A
Explanation:
1 joule=1N-m/s; W=F*S;.
7.
When the expansion or compression takes place according to the law pvn = C, the
process is known as
A. isothermal process
B. adiabatic process
C. hyperbolic process
D. polytrophic process
Answer: Option D
Explanation:
polytrophic process
8.
The entropy is a point function and thus it is a property of the same.
A. Correct B. Incorrect
Answer: Option A
Explanation:
Because s=dq/dt its unit is j/kgk it is a point of graph of t-s diagram which give result of
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area under its curve as heat transfer.
9.
The state of a substance whose evaporation from its liquid state is complete, is known as
A. Vapour
B. perfect gas
C. Air
D. Steam
Answer: Option B
Explanation:
perfect gas
10.
An open cycle gas turbine works on
A. Carnot cycle
B. Otto cycle
C. Joule's cycle
D. Stirling cycle
Answer: Option C
Explanation:
Open cycle gas turbine works on bratton cycle (or joule cycle) which consists two constant pressure
processes and two isentropic processes. Working gas is air. In this cycle, air in the atmosphere is
drawn and the gas at outlet of turbine is released in atmosphere.
11.
The volumetric or molar specific heat at constant pressure is the product of
A. molecular mass of the gas and the specific heat at constant volume
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B. atomic mass of the gas and the gas constant
C. molecular mass of the gas and the gas constant
D. none of the above
Answer: Option D
Explanation:
Molar specific heat at constant pressure:
(cp)mol = y*R/(y-1).
Where,
R = universal gas constant.
y = specific heat ratio = cp/cv.
12.
The efficiency of Carnot cycle depends upon
A. temperature limits
B. pressure ratio
C. volume compression ratio
D. cut-off ratio and compression ratio
Answer: Option A
Explanation:
Efficiency of Carnot Cycle = 1- (T2/T1).
Therefore Efficiency of Carnot Cycle is function of temperature.
13.
The gas turbine cycle with regenerator improves
A. thermal efficiency
B. work ratio
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C. avoids pollution
D. none of these
Answer: Option A
Explanation:
In regenerative we heat up the air coming from the compressor before sending into the
combustion chamber with the help of the exhaust gases coming from the turbine.
Hence the fuel consumption in the combustion chamber reduces resulting increase in
thermal efficiency.
14.
Which of the following has the highest calorific value?
A. Peat
B. Lignite
C. Bituminous coal
D. Anthracite coal
Answer: Option D
Explanation:
Anthracite coal
15.
When a gas is heated, change takes place in
A. pressure
B. volume
C. temperature
D. all of these
Answer: Option D
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16.
Which of the following is an intensive property of a thermodynamic system?
A. Volume B. Temperature
C. Mass D. Energy
Answer: Option B
Explanation:
Temperature
17.
A triatomic molecule consists of __________ atoms.
A. One B. two
C. Three D. four
Answer: Option C
Explanation:
Three
18.
The main cause for the irreversibility is
A. mechanical and fluid friction
B. unrestricted expansion
C. heat transfer with a finite temperature difference
D. all of the above
Answer: Option D
Explanation:
all of the above
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19.
A cycle consisting of __________ and two isothermal processes is known as Stirling
cycle.
A. two constant pressure
B. two constant volume
C. two isentropic
D. one constant pressure, one constant volume
Answer: Option B
Explanation:
two constant volume
20.
The heat and mechanical energies are mutually convertible. This statement was
established by
A. Boyle
B. Charles
C. Joule
D. none of these
Answer: Option C
Because first law of thermodynamic developed on joules law.
21.
For the same compression ratio, the efficiency of Diesel cycle is __________ Otto cycle.
A. greater than
B. less than
C. equal to
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Answer: Option B
less than
22.
Mond gas is obtained by
partial combustion of coal, coke, anthracite coal or charcoal in a mixed air
A.
steam blast
B. carbonization of bituminous coal
C. passing steam over incandescent coke
D. passing air and a large amount of steam over waste coal at about 650°C
Answer: Option D
Explanation:
passing air and a large amount of steam over waste coal at about 650°C
23.
The natural solid fuel is
A. Wood
B. Coke
C. anthracite coal
D. pulverized coal
Answer: Option A
Explanation:
Wood
24.
The condition for the reversibility of a cycle is
A. the pressure and temperature of the working substance must not differ,
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appreciably, from those of the surroundings at any stage in the process
all the processes, taking place in the cycle of operation, must be extremely
B.
slow
C. the working parts of the engine must be friction free
D. all of the above
Answer: Option D
Explanation:
all of the above
25.
In open cycle gas turbine plants
A. the indirect heat exchanger and cooler is avoided
B. direct combustion system is used
C. a condenser is used
D. all of the above
Answer: Option D
all of the above
26.
In an isolated system, neither the heat and work nor the, mass of the working substance
crosses the boundary of the system.
A. True B. False
Answer: Option A
Explanation:
True
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27.
The compression ratio is the ratio of
A. swept volume to total volume
B. total volume to swept volume
C. swept volume to clearance volume
D. total volume to clearance volume
Answer: Option D
Explanation:
Compression ratio = Total volume/Clearance volume.
Total volume-Clearance volume = Swept volume.
28.
When a fluid is allowed to expand suddenly into a vaccum chamber through an orifice of
large dimensions, the process is known as free expansion process.
A. True B. False
Answer: Option A
Explanation:
True
29.
The efficiency of Ericsson cycle is __________ Carnot cycle.
A. greater than
B. less than
C. equal to
Answer: Option C
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Explanation:
equal to
30.
One molecule of oxygen consists of __________ atoms of oxygen.
A. 2 B. 4
C. 8 D. 16
Answer: Option A
O + O = O2.
16/16 + 16/16 = 32/16.
1 + 1 = 2.
O2 = 2.
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SOLUTIONS
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