Explore topic-wise MCQs in Thermodynamics.

This section includes 248 Mcqs, each offering curated multiple-choice questions to sharpen your Thermodynamics knowledge and support exam preparation. Choose a topic below to get started.

201.

The entropy changes for the universe during the process in kJ/K is

A. 0.4652
B. 0.0067
C. 0
D. 0.6711
Answer» B. 0.0067
Discussion
202.

A gas expands in a friction less piston-cylinder arrangement. The expansion process is very slow, and is resisted by an ambient pressure of 100 kPa. During the expansion process, the pressure of the system (gas) remains constant at 300 kPa. The change in volume of the gas is 0.01 m

A. 0 kJ
B. 1 kJ
C. 2 kJ
D. 3 kJ
Answer» D. 3 kJ
Discussion
203.

A gas contained in a cylinder is compressed, the work required for compression being 5000 kJ. During the process, heat interaction of 2000 kJ causes the surroundings to be heated. The changes in internal energy of the gas during the process is

A. 7000 kJ
B. 3000 kJ
C. +3000 kJ
D. +7000 kJ
Answer» E.
Discussion
204.

Temperature of nitrogen in a vessel of volume 2 m

A. 4.55
B. 5.55
C. 4.65
D. 4.59
Answer» B. 5.55
Discussion
205.

The contents of a well-insulated tank are heated by a resistor of 23 in which 10 A current is flowing. Consider the tank along with its contents as a thermodynamic system. The work done by the system and the heat transfer to the system are positive. The rates of heat (Q), work (W) and change in internal energy ( U) during the process (kW) are

A. Q = 0, W = 2.3, U = +2.3
B. Q = +2.3, W = 0, U = +2.3
C. Q = 2.3, W = 0, U = 2.3
D. Q = 0, W = + 2.3, U = 2.3
Answer» B. Q = +2.3, W = 0, U = +2.3
Discussion
206.

With increasing temperature of intake air, CI engine efficiency

A. decreases
B. increases
C. remains same
D. depends on other factors
Answer» B. increases
Discussion
207.

An air standard diesel cycle consists of

A. Two adiabatic and two constant volume processes
B. Two constant volume and two isothermal processes
C. One constant pressure, one constant volume and two adiabatic processes
D. One constant pressure, one constant volume and two isothermal processes
Answer» D. One constant pressure, one constant volume and two isothermal processes
Discussion
208.

Consider a Rankine cycle with superheat. If the maximum pressure in the cycle is increased without changing the maximum temperature and the minimum pressure, the dryness fraction of steam after the isentropic expansion will increase

A. TRUE
B. FALSE
C. TRUE or FALSE
D. None of these
Answer» C. TRUE or FALSE
Discussion
209.

A gas turbine cycle with infinitely large number of stages during compression and expansion leads to

A. Stirling cycle
B. Atkinson cycle
C. Ericson cycle
D. Brayton cycle
Answer» D. Brayton cycle
Discussion
210.

A gas turbine cycle with heat exchange and reheating improves

A. Only the thermal efficiency
B. Only the specific power output
C. Both thermal efficiency and specific power output
D. Neither thermal efficiency nor specific power output
Answer» D. Neither thermal efficiency nor specific power output
Discussion
211.

An isolated thermodynamic system executes a process. Choose the correct statement (s) from the following

A. No heat is transferred
B. No work is done
C. No mass flows across the boundary of the system
D. No Chemical reaction takes place within the system
E. ( a , b , c )
Answer» F.
Discussion
212.

Air expands steadily through a turbine from 6 bar, 800 K to 1 bar, 520 K. During the expansion, heat transfer from air to the surroundings at 300 K is 10 kJ/kg air. Neglect the changes in kinetic and potential energies and evaluate the irreversibility per kg air. Assume air to behave as an ideal gas with c

A. <table><tr><td rowspan="2">I = 300</td><td rowspan="2"><img src="https://www.indiabix.com/_files/images/data-interpretation/common/15-sym-oparen-h1.gif"></td><td rowspan="2">C<sub>p</sub>ln</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>T<sub>2</sub></center></td><td rowspan="2"> - Rln</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>P<sub>2</sub></center></td><td rowspan="2"><img src="https://www.indiabix.com/_files/images/data-interpretation/common/15-sym-cparen-h1.gif"></td><td rowspan="2"> + </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>10</center></td></tr><tr><td style="text-align: center;">T<sub>1</sub></td><td style="text-align: center;">P<sub>1</sub></td><td style="text-align: center;">300</td></tr></table>
B. <table><tr><td rowspan="2">I = 100</td><td rowspan="2"><img src="https://www.indiabix.com/_files/images/data-interpretation/common/15-sym-oparen-h1.gif"></td><td rowspan="2">C<sub>p</sub>ln</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>T<sub>2</sub></center></td><td rowspan="2"> - Rln</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>P<sub>2</sub></center></td><td rowspan="2"><img src="https://www.indiabix.com/_files/images/data-interpretation/common/15-sym-cparen-h1.gif"></td><td rowspan="2"> + </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>300</center></td></tr><tr><td style="text-align: center;">T<sub>1</sub></td><td style="text-align: center;">P<sub>1</sub></td><td style="text-align: center;">10</td></tr></table>
C. <table><tr><td rowspan="2">I = 300</td><td rowspan="2"><img src="https://www.indiabix.com/_files/images/data-interpretation/common/15-sym-oparen-h1.gif"></td><td rowspan="2">C<sub>p</sub>ln</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>T<sub>1</sub></center></td><td rowspan="2"> - Rln</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>P<sub>2</sub></center></td><td rowspan="2"><img src="https://www.indiabix.com/_files/images/data-interpretation/common/15-sym-cparen-h1.gif"></td><td rowspan="2"> + </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>10</center></td></tr><tr><td style="text-align: center;">T<sub>2</sub></td><td style="text-align: center;">T<sub>1</sub></td><td style="text-align: center;">300</td></tr></table>
D. <table><tr><td rowspan="2">I = 300</td><td rowspan="2"><img src="https://www.indiabix.com/_files/images/data-interpretation/common/15-sym-oparen-h1.gif"></td><td rowspan="2">C<sub>p</sub>ln</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>T<sub>1</sub></center></td><td rowspan="2"> - Rln</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>P<sub>1</sub></center></td><td rowspan="2"><img src="https://www.indiabix.com/_files/images/data-interpretation/common/15-sym-cparen-h1.gif"></td><td rowspan="2"> + </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td></tr><tr><td style="text-align: center;">T<sub>2</sub></td><td style="text-align: center;">P<sub>2</sub></td><td style="text-align: center;">3</td></tr></table>
Answer» B. <table><tr><td rowspan="2">I = 100</td><td rowspan="2"><img src="https://www.indiabix.com/_files/images/data-interpretation/common/15-sym-oparen-h1.gif"></td><td rowspan="2">C<sub>p</sub>ln</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>T<sub>2</sub></center></td><td rowspan="2"> - Rln</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>P<sub>2</sub></center></td><td rowspan="2"><img src="https://www.indiabix.com/_files/images/data-interpretation/common/15-sym-cparen-h1.gif"></td><td rowspan="2"> + </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>300</center></td></tr><tr><td style="text-align: center;">T<sub>1</sub></td><td style="text-align: center;">P<sub>1</sub></td><td style="text-align: center;">10</td></tr></table>
Discussion
213.

A piston-cylinder device initially contains 0.4 m

A. 55.45 kJ
B. -21.45 kJ
C. -55.45 kJ
D. -15.45 kJ
Answer» D. -15.45 kJ
Discussion
214.

In the case of a refrigeration system undergoing an irreversible cycle,
Q
 is ....(< 0/ = 0/ > 0)
T
A. <table><tr><td rowspan="2"> </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> Q</center></td><td rowspan="2"> &lt; 0 </td></tr><tr><td style="text-align: center;">T</td></tr></table>
B. <table><tr><td rowspan="2"> </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> Q</center></td><td rowspan="2"> &gt; 0 clausius inequality</td></tr><tr><td style="text-align: center;">T</td></tr></table>
C. Q > 0
D. Q = 0
Answer» B. <table><tr><td rowspan="2"> </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> Q</center></td><td rowspan="2"> &gt; 0 clausius inequality</td></tr><tr><td style="text-align: center;">T</td></tr></table>
Discussion
215.

A heat reservoir at 900 K is brought into contact with the ambient at 300 K for a short time. During this period 9000 kJ of heat is lost by the heat reservoir. The total loss in availability due to this process is

A. 18000 kJ
B. 9000 kJ
C. 6000 kJ
D. None of these
Answer» D. None of these
Discussion
216.

A cycle heat engine does 50 kJ of work per cycle. If the efficiency of the heat engine is 75%. The heat rejected per cycle is

A. <table><tr><td rowspan="2">16</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>2</center></td><td rowspan="2"> kJ</td></tr><tr><td style="text-align: center;">3</td></tr></table>
B. <table><tr><td rowspan="2">33</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td><td rowspan="2"> kJ</td></tr><tr><td style="text-align: center;">3</td></tr></table>
C. <table><tr><td rowspan="2">37</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td><td rowspan="2"> kJ</td></tr><tr><td style="text-align: center;">2</td></tr></table>
D. <table><tr><td rowspan="2">66</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td><td rowspan="2"> kJ</td></tr><tr><td style="text-align: center;">2</td></tr></table>
Answer» B. <table><tr><td rowspan="2">33</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td><td rowspan="2"> kJ</td></tr><tr><td style="text-align: center;">3</td></tr></table>
Discussion
217.

For two cycles coupled in series, the topping cycle has an efficiency of 30% and the bottoming cycle has an efficiency of 20%. The overall combined cycle efficiency is

A. 50%
B. 44%
C. 38%
D. 55%
Answer» C. 38%
Discussion
218.

Any thermodynamic cycle operating between two temperature limits is reversible if the product of the efficiency when operating as a heat engine and the COP when operating as a refrigerator is equal to l.

A. True
B. True/False
C. False
D. Both
Answer» D. Both
Discussion
219.

When a system executes an irreversible cycle

A. <table><tr><td rowspan="2"> </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> Q</center></td><td rowspan="2"> &lt; 0</td></tr><tr><td style="text-align: center;">T</td></tr></table>
B. dS > 0
C. <table><tr><td rowspan="2"> </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>dQ</center></td><td rowspan="2"> = 0</td></tr><tr><td style="text-align: center;">T</td></tr></table>
D. <table><tr><td rowspan="2"> </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> Q</center></td><td rowspan="2"> &gt; 0</td></tr><tr><td style="text-align: center;">T</td></tr></table>
Answer» B. dS > 0
Discussion
220.

A reversible heat transfer demands :

A. The temperature difference causing heat transfer tends to zero
B. The system receiving heat must be at a constant temperature
C. The system transferring out heat must be at a constant temperature
D. Both interacting systems must be at constant temperatures
Answer» B. The system receiving heat must be at a constant temperature
Discussion
221.

A solar energy based heat engine which receives 80 kJ of heat at 100 C and rejects 70 kJ of heat to the ambient at 30 C is to be designed. The thermal efficiency of the heat engine is

A. 70%
B. 18.8%
C. 12.5%
D. Indetermine
Answer» D. Indetermine
Discussion
222.

At the triple point of a pure substance, the number of degrees of freedom is

A. 0
B. 1
C. 2
D. 3
Answer» B. 1
Discussion
223.

Which among the following is the boiler mounting?

A. Blow off cock
B. Feed pump
C. Economizer
D. Super heater
Answer» B. Feed pump
Discussion
224.

The equivalent evaporation (kg/hr) of a boiler producing 2000 kg/hr of steam with enthalpy content of 2426 kJ/kg from feed water at temperature 40 C (liquid enthalpy =168 kJ/kg) is (enthalpy of vaporization of water at 100 C = 2258 kJ/kg)

A. 2000
B. 2149
C. 186
D. 1649
Answer» B. 2149
Discussion
225.

The isentropic heat drop in the nozzle of an impulse steam turbine with a nozzle efficiency 0.9, blade velocity ratio 0.5 and mean blade velocity 150 m/s in kJ/kg is

A. 50
B. 40
C. 60
D. 75
Answer» B. 40
Discussion
226.

List-IList-ll
A. Steam nozzle 1. Mach number
B. Compressible 2. Reaction turbine
C. Surface tension3. Biot number
D. Heat conduction4. Nusselt number
5. Super saturation
6. Weber number
A. A-5, B-1, C-6, D-3
B. A-1, B-1, C-6, D-4
C. A-5, B-2, C-6, D-1
D. A-6, B-1, C-2, D-3
Answer» B. A-1, B-1, C-6, D-4
Discussion
227.

In steam and other vapour cycle, the process of removing non-condensable is called

A. Scavenging process
B. Deaeration process
C. Exhaust process
D. Condensation process
Answer» C. Exhaust process
Discussion
228.

In a Rankine cycle heat is added

A. Reversibly at constant volume
B. Reversibly at constant temperature
C. Reversibly at constant pressure and temperature
D. Reversibly at constant pressure
Answer» E.
Discussion
229.

A frictionless piston-cylinder device contains a gas initially at 0.8 MPa and 0.015 m

A. 8.32
B. 12.00
C. 554.67
D. 8320.00
Answer» B. 12.00
Discussion
230.

A balloon containing an ideal gas is initially kept in an evacuated and insulated room. The balloon ruptures and the gas fills up the entire room. Which one of the following statements is TRUE at the end of above process?

A. The internal energy of the gas decreases from its initial value, but the enthalpy remains constant.
B. The internal energy of the gas increases from its initial value, but the enthalpy remains constant.
C. Both internal energy and enthalpy of the gas remain constant
D. Both internal energy and enthalpy of the gas increase
Answer» D. Both internal energy and enthalpy of the gas increase
Discussion
231.

If the specific heats of the working fluid are constant and the value of specific heat ratio is 1.4, the thermal efficiency (%) of the cycle is

A. 21
B. 40.9
C. 42.6
D. 59.7
Answer» B. 40.9
Discussion
232.

The above cycle is represented on T-s plane by

A. <img src="http://images.interviewmania.com/wp-content/uploads/2019/10/as-14.jpg">
B. <img src="http://images.interviewmania.com/wp-content/uploads/2019/10/as-15.jpg">
C. <img src="http://images.interviewmania.com/wp-content/uploads/2019/10/as-16.jpg">
D. <img src="http://images.interviewmania.com/wp-content/uploads/2019/10/as-17.jpg">
Answer» D. <img src="http://images.interviewmania.com/wp-content/uploads/2019/10/as-17.jpg">
Discussion
233.

During the phase change of a pure substance

A. dG = 0
B. dP = 0
C. dH = 0
D. dU= 0
Answer» C. dH = 0
Discussion
234.

Availability of a system at any given state is

A. a property of the system
B. the maximum work obtainable as the system goes to dead state
C. the total energy of the system
D. the maximum useful work obtainable as the system goes to dead state
Answer» E.
Discussion
235.

In adiabatic flow with friction, the stagnation temperature along a streamline.... (increase/ remain constant)

A. Remain constant
B. increase
C. decrease
D. None of these
Answer» B. increase
Discussion
236.

Subsonic and supersonic diffusers have the following geometry.

A. Divergent and convergent respectively
B. Both divergent
C. Both convergent
D. Convergent and divergent respectively
Answer» E.
Discussion
237.

In the Rankine cycle when superheated steam is used

A. Thermal efficiency increases
B. Steam consumption decreases
C. Steam dryness after expansion increases
D. All of the above
Answer» E.
Discussion
238.

In a gas turbine power plant intercooler are used to cool the ____ in order to decrease the ______.

A. hot gases
B. compressed air
C. expansion work
D. compression work
E. Compressed air ; compression work
Answer» F.
Discussion
239.

The fundamental objective of employing the condenser in a steam power plant is to _____ (reduce/increase) the dryness fraction of steam.

A. increase
B. reduce
C. decrease
D. increase and decrease
Answer» C. decrease
Discussion
240.

A reversible thermodynamic cycle containing only three processes and producing work is to be constructed. The constraints are:

A. 1
B. 2
C. 3
D. 4
Answer» B. 2
Discussion
241.

A steel ball of mass 1 kg of specific heat 0.4 kJ/ kgK is at a temperature of 60 C. It is dropped into 1 kg water at 20 C. The final steady state temperature of water is

A. 23.5 C
B. 30 C
C. 35 C
D. 40 C
E. None of these
Answer» F.
Discussion
242.

In the vicinity of the triple point, the vapour pressures of liquid and solid ammonia are respectively given by ln P= 15.16 3063/T and In P= 18.70 3754/T where P is in atmospheric and T is in kelvin. What is the temperature at the triple point?

A. 95.2 K
B. 19.2 K
C. 195.2 K
D. 115.2 K
Answer» D. 115.2 K
Discussion
243.

When initially dry and saturated steam flows through a nozzle, the ratio of actual discharge to calculated discharge is

A. Equal to 1.0
B. Greater than 1.0
C. Less than 1.0
D. Independent of inlet conditions
Answer» C. Less than 1.0
Discussion
244.

Nitrogen gas (molecular weight 28) is enclosed in a cylinder by a piston, at the initial condition of 2 bar, 298 K and 1 m

A. 200 kJ
B. 138.6 kJ
C. 2 kJ
D. 200 kJ
Answer» C. 2 kJ
Discussion
245.

A 2 kW, 40 litres water heater is switched on for 20 minutes. The heat capacity cp for water is 4.2 kJ/kgK. Assuming all the electrical energy has gone into heating the water, increase of the water temperature in degree centigrade is

A. 2.7
B. 4.0
C. 14.3
D. 25.25
Answer» D. 25.25
Discussion
246.

A mixture of ideal gases has the following composition by mass :

A. 274.996
B. 247.996
C. 374.996
D. 174.996
Answer» B. 247.996
Discussion
247.

A condenser of a refrigeration system rejects heat at a rate of 120 kW, while is compressor consumes a power of 30 kW. The coefficient of performance of the system would be

A. <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td></tr><tr><td style="text-align: center;">4</td></tr></table>
B. 4
C. <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td></tr><tr><td style="text-align: center;">3</td></tr></table>
D.
E. 3
Answer» E. 3
Discussion
248.

The first law of thermodynamics takes the form W = H when applied to

A. A closed system undergoing a reversible adiabatic process
B. An open system undergoing an adiabatic process with negiigible changes in kinetic and potential energies
C. A closed system undergoing a reversible constant volume process
D. A closed system undergoing a reversible constant pressure process.
Answer» C. A closed system undergoing a reversible constant volume process
Discussion