THERMODYNAMICS
THERMODYNAMICS
(CLASS WORK OBJECTIVE & PRACTICE QUESTIONS)
CONTENTS
Unit Chapters Page No.
1 Basic Concepts 2-7
2 Work & Heat 8 - 19
3 First Law of Thermodynamics 20 - 25
4 Second Law of Thermodynamics 26 - 37
5 Entropy 38 - 45
6 Availability 46 - 49
7 Properties of Pure Substances 50 - 56
8 Air Cycles 57 - 67
9 Rankine Cycles 68 - 80
10 Refrigeration 81 - 85
11 Psychrometry 86 - 90
Copyright Ascent Gate Academy 2013
All rights reserved.
No part of this publication may be reproduced, stored in a retrieval system, or
transmitted, in any form or by any means, electronic, mechanical, photocopying, digital,
recording, without the prior permission of the publishers.
Published at : Ascent Gate Academy
“Shraddha Saburi”, Near Gayatri Vidyapeeth,
Rajnandgaon (Chhattisgarh) Mob : 09993336391
www.ascentgateacademy.com Copyright : Ascent Gate Academy 1
THERMODYNAMICS
1 BASIC CONCEPTS
(CLASS WORK OBJECTIVE)
1. A body of weight 100 N falls freely a vertical distance of 50 m The atomospheric drag force is 0.5 N,
For the body, the work interaction is [GATE-ME-93]
a) +5000 J b) -5000J’ c) -25 J d) + 25 J
2. The specific heats of an ideal gas depend on its [GATE-ME-96]
a) Temperature b) Pressure
c) Volume d) Molecular weight and structure
3. Pressure reaches a value of absolute zero.
(a) at a temperature of -273K (b) under vaccum condition
(c) at the earth’s centre
(d) when molecular momentum of system becomes zero
4. The value of compressibility factor for an ideal gas may be:
1. less or more than one 2. equal to one
3. zero 4. less than zero
The correct value (s) is / are given by
(a) 1 and 2 (b) 1 and 4 (c) 3 only (d) 2 only
5. Match list I (Type of thermometer) with list II (Thermometric property) and select the correct answer
using thecode given below the lists:
list - I list - II
A. Mercury - in - glass 1. Pressure
B. Thermocouple 2. Electrical resistance
C. Thermistor 3. Volume
D. Constant volume 4. Induced electric gas-voltage
codes:
ABCD
(a) 1 4 2 3
(b) 3 2 4 1
(c) 1 2 4 3
(d) 3 4 2 1
6. Assertion (A): Ratio of specific heats Cp/Cv decreases with increases in temperature.
Reason (R): With increase in temperature, Cp decreases at a higher a rate than Cv.
(a) BothA and R are individually true and R is the correct explanation ofA.
(b) Both A and R are true but R is not the correct explanation of A.
(c)A is true but R is false
(d)A is false but R is true.
7. A 4 kW, 20 litre water heater is switched on for 10min. The heat capacity Cp for water is 4 kJ/kg K.
Assuming all the electrical energy has gone into heating the water what is the increase of the water
temperature? (b) 20oC (c) 26oC (d) 30oC
(a) 15oC
www.ascentgateacademy.com Copyright : Ascent Gate Academy 2
THERMODYNAMICS
8. An insulated box containing 0.5kg of a gas having Cv= 0.98 kJ/kg.K falls from a ballon 4km above
the earth’s surface.what will be the temperature rise of the gas when the box hits the ground.
(a) 0 K (b) 20 K (c) 40 K (d) 60 K
Statement for Linked Answer Questions 09 & 10 :
A football was inflated to a gauge pressure of 1 bar when the ambient temperature was 150C. When
the game stared next day, the air temperature at the stadium was 50C.Assume that the football remains
constant at 2500cm3.
9. The amount of heat lost by the air in the football and the gauge pressure of air in the football at the
stadium respectivelyequal [GATE-ME-06]
a) 30.6 J, 1.94 bar b) 21.8, 0.93 bar
c) 61.1 J, 1.94 bar d) 43.7 J, 0.93 bar
10. Gauge pressure of air to which the ball msut have been originally inflated so that it would equal 1 bar
gauge at the stadium is [GATE-ME-06]
a) 2.23 bar b) 1.94 bar c) 1.07 bar d) 1.00 bar
************************
www.ascentgateacademy.com Copyright : Ascent Gate Academy 3
THERMODYNAMICS
1 BASIC CONCEPTS
PRACTICE QEUSTIONS
1. The correct sequence of the decreasing order of the value of characteristic gas constants of the given
is.
(a) hydrogen,nitrogen,air, carbon - dioxide. (b) carbon dioxide, hydrogen,nitrogen, air
(c) air, nitrogen, carbondioxide,hydrogen (d) nitrogen, air, hydrogen, carbon dioxide.
2. Which one of the following is the extensive property of a thermodynamic system ?
(a) Volume (b) Pressure (c) Temperature (d) Density
3. Which one of the following are intensive properties ?
1. Kinetic energy 2. Specific Enthalpy 3. Pressure 4. Entropy
Select the correct answer using the code given below.
(a) 1 and 3 (b) 2 and 3 (c) 1,3 and 4 (d) 2 and 4
4. Which one of the following is the characterisitic equation of a real gas ?
(a) (P+ (a/V2) (v - b) = RT (b) (P+ (a/V2)(v + b) = RT \
(c) pv = RT (d) pv = nRT
5. A thermodynamic engine which consists of two dissimilar electric conductors connected at two
junctions maintained at different temperatures, converts.
(a) Electric energy into heat energy (b) Heat energy into electric energy
(c) Mechanical work into electric energy (d) Electric energyinto mechanical work.
6 Assertion (A):At very high densities, compressibility of a real gas is less than one.
Reason (R) :As the temperature is considerably reduced, the molecules are brought closer together
and thermo nuclear attractive forces become greater at pressure around 4 MPa.
(a) BothA and R are individually true and R is the correct explanation ofA.
(b) Both A and R are true but R is not the correct explanation of A.
(c)A is true but R is false
(d) Ais false but R is true.
7. Which of the following are intensive properties ?
1. Kinetic energy 2. Thermal conductivity 3. Pressure 4. Entropy
Select the correct answer using the code given below:
(a) 1 and 2 (b) 2 and 3 only (c) 2 , 3 and 4 (d) 1 , 3 and 4
8. Ice kept in a well insulated thermo flask is an example of which system ?
(a) closed system (b) isolated system
(c) Open system (d) Non-flow adiabatic system
9. Measurement of temperature is based on which law of thermodynamics ?
(a) Zeroth law of thermodynamics (b) First law of thermodynamics
(c) Second law of thermodynamics (d) Third law of thermodynamics
10. The compressibility factor for Nitrogen (N2) is 1.08 the density of N2 at 275 bar and 170C is equal to
(a) 320 kg / m3 (b) 269 kg / m3 (c) 300 kg / m3 (d) 296 kg m3
www.ascentgateacademy.com Copyright : Ascent Gate Academy 4
THERMODYNAMICS
11. Match list - I with list - II and select the correct answer using the codes given below the lists;
list - I list - II
(Parameter) (Property)
A. Volume - 1. Path function
B. Density - 2. Intensive property
C. Pressure - 3. Extensive property
D. Work - 4. Point function
Codes:
ABCD
(a) 3 2 4 1
(b) 3 2 1 4
(c) 2 3 4 1
(d) 2 3 1 4
12. Assertion (A): During the temperature measurement of hot gas in a duct that has relatively cool walls,
the temperature indicated by the thermometer will be lower than the true hot gas temperature.
Reason (R) : The sensing tip of thermometer receives energy from the hot gas and loses heat to the
duct walls.
13. Two blocks which are at different states are bought into contact with each other and allowed to reach
a final state of thermal equilibrium. The final temperature attained is specified by the.
(a) Zeroth law of thermodynamics (b) First law of thermodynamics
(c) Second law of thermodynamics (d) Third law of thermodynamics
14. Consider an ideal gas contained in vessel. If intermolecular interaction suddenlybegins to act, which of
the following happens ?
(a) The pressure increase
(b) The pressure remains unchanged
(c) The pressure decrease
(d) The gas collapses
15. Variation of pressure and volume at constant temperature are correlated through.
(a) Charle’s law (b) Boyle’s law (c) Joule’s law (d)Gay Lussac’s law
16. Which one of the following is the extensive property of a thermodynamic system ?
(a) volume (b) Pressure (c) Temperature (d) Density
17. A closed thermodynamic system is one in which.
(a) There is no energy or mass transfer across the boundary.
(b) There is no mass transfer, but energy transfer exists.
(c) There is no energy transfer, but mass transfer exists.
(d) Both energy and mass transfer take place across the boundary, but the mass transfer is controlled
by valves.
18. The internal energy of a gas obeying van der Waals equation (P+ (a/V2)(v-b) = RT depends on its.
(a) temperature (b) temperature and pressure
(c) temperature and specific volume. (d) pressure and specific volume.
www.ascentgateacademy.com Copyright : Ascent Gate Academy 5
THERMODYNAMICS
19. Consider the following statements;
A real gas obeys perfect gas law at very
1. high temperatures 2. high pressure 3. low pressures
Which of these statements is / are correct?
(a) 1 alone (b) 1 and 3 (c) 2 alone (d) 3 alone
20. Pressure reaches a value of absolute zero.
(a) at a temperature of -273K
(b) under vaccum condition
(c) at the earth’s centre
(d) when molecular momentum of system becomes zero
21. The compressibility factor for a real gas is
(a) PV /RT and should always be a fraction only (b) PR/VT and should always be unity only.
(c) PV/RT and should always be more than unity (d) PT/VR and should always be more than unity
22. The energy is an X property and the temperature is an Y property. The words X and Y respecitvely
are.
(a) intensive and extensive (b) intensive and intensiv
(c) extensive and extensive (d) extensive and intensiv
23. Match List I with List - II [GATE-ME-96]
List - I List - II
A. Cetane number 1. Ideal gas
B. Approach and range 2. Vander Waals gas
T 0 3. S.I. engine
C. P
h
D. dh = cp dT, even when pressure varies 4. C.I. engine
5. Cooling towers
6. Heat exchangers
24. Volume is used as thermodynamic property in which of the following thermometer ?
(a) constant volume gas thermometer (b) constant pressure gas thermometer
(c) thermocouple (d) mercury -in-glass thermometer.
25. A system is said to be in thermodynamic equilibrium when.
(a) there is no work transfer.
(b) there is no heat transfer.
(c) internal energy of the system is zero.
(d) no change in macroscopic property is registered.
26. Which of the following is not a property ?
(a) heat (b) volume (c) pressure (d) temperature
27. Air cooler can be considered as .
(a) open system (b) closed system (c) isolated system (d) None of these
www.ascentgateacademy.com Copyright : Ascent Gate Academy 6
THERMODYNAMICS
28. Match list Aan list B :-
AB
(I) Intensive property - (i) Volume
(II) Extensive property - (ii) Heat
(III) Path function - (iii) Specific Volume.
(IV) Isolated system - (iv) Thermal flask
(A) (I) - (i), (II) - (ii), (III) - (iii),(IV) - (iv) (B) (I) - (ii), (II) - (i), (III) - (iv),(IV) - (iii)
(C) (I) - (iii), (II) - (i), (III) - (ii),(IV) - (iv) (D) (I) - (iii), (II) - (i), (III) - (iv),(IV) - (ii)
29. If dk = k2 - k1, which is the following is not true ?
(a) K is a point function
(b) K depends on the path followed by the system.
(c) K is the property of the system
(d) None of the above.
30. Gas equation PV=mRT hold good for.
(a) mono atomic gases (b) ideal gases (c) real gases (d) mixture of gases.
31. An insulated rigid vessel contains a maxiure of fuel and air. The mixure is ignited bya minute spark. The
contents of the vesssel experience. [GATE-ME-93]
a) Increase in temperature, pressure and energy
b) Decrease in temperature, pressure and energy
c) Increase in temperature and pressure but no change in energy
d) Increase in temperature and pressure but decrease in energy
***********
“Man’s mind, once stretched by a new idea,
never regains its original dimensions”
1. BASIC CONCEPTS (Practice Questions) Ans. :
1-a, 2-a, 3-b, 4-a, 5-b, 6-a, 7-b, 8-b, 9-a, 10-d, 11-a, 12-T,F, 13-b, 14-c, 15-b, 16-a, 17-b, 18-a,
19-b, 20-d, 21-a, 22-d, 23-A4, B5, C2, D1, 24-b, 25-d, 26-a, 27-a, 28-c, 29-c, 30-b, 31-a
www.ascentgateacademy.com Copyright : Ascent Gate Academy 7
THERMODYNAMICS
2 WORK & HEAT
(CLASS WORK OBJECTIVE)
1. A gas expands from pressure P1 to pressure P2 (P2 = P1/10 ). If the process of expansion is
isothermal, the volume at the end of expansion is 0.55 m3. If the process of expansion is adiabatic, the
volume at the end of expansion will be closed to.
(a) 0.45 m3.
(b) 0.55 m3.
(c) 0.65 m3.
(d) 0.28 m3.
2. An ideal cycle is shown in the fig. Its thermal efficiencyis given by.
P
2
pV= C
13
V
( )v3 - 1 (( ))(b) 1-1v3 - 1 (c) 1 - (v3 - v1 ) p1 (d) 1- (p2 - p1 ) v1
v1 v1
(p2 - p1 ) v1 (v3 - v1 ) p1
(a) p2 -1
p1
( )p2 -1
p1
3. Asystem while undergoing a cycleA-B-C-D-Ahas the values of heat and work transfers as given in
the table.
Process Q kJ/min W kJ/min
A-B + 687 + 474
B-C - 269 0
C-D - 199 - 180
D-A + 75 0
The power developed in kW is, nearly,
(a) 4.9
(b) 24.5
(c) 49
(d) 98
www.ascentgateacademy.com Copyright : Ascent Gate Academy 8
THERMODYNAMICS
4. An ideal gas undergoes an isothermal expansion from state R to state S in a turbine as shown in the
diagram given below: R
2.0
1.0 S
p3bar
0.1 0.2 v(m3)
The area of shaded region is 1000Nm. What is the amount is turbine work done during the process ?
(a) 14,000 (b) 12,000 (c) 11,000 (d) 10,000
5. One kg of ice at 0oC is completely melted into water at 0oC at 1 bar pressure. The latent heat of
fusion of water is 333 kJ/kg and the densities of water and ice at 0oC are 999.0 kg/m3 and
916.0 kg/m3, respectively. What are the approximate values of the work done and energy transferred
as heat for the process, respectively ?
(a) -9.4 J and 333.0 kJ (b) 9.4 J and 333.0 kJ
(c) 333.0 kJ and - 9.4 J (d) None of the above
6. A balloon which is initially collapsed and flat is slowly filled with a gas at 100 kPa so as to form it into
a sphere of 1m radius. What is the work done by the gas in the balloon during the filling process?
(a) 428.9 kJ (b) 418.9 kJ (c) 420.9 kJ (d) 416.9 kJ
7. Two ideal heat engine cycles are represented in the given fig. Assume VQ = QR, PQ = QS and
UO = PR = RT. If the work interaction for the rectangular cycle (WVUR) is 48 Nm, then the work
Interaction for the other cycle PST is.
(a) 12 Nm W VS
(b) 18 Nm Pressure
(c) 24 Nm
(d) 36 Nm Q T
U P R
8. An ideal gas with initial volume, pressure and tempera tVuorelumofe0.1m3, 1 bar and 27oC respectively is
compressed in a cylinder by a piston such that its final volume and pressure are 0.04 m3 and 5 bars
respectively, then its final temperature will be. (b) 54o C
(a) 123o C (d) 600o C
(c) 327o C
9. A system at a given state undergoes change through the following expansion processes to reach the
same final
volume.
1. Isothermal 2. Isobaric
3. Adiabatic (y = 1.4) 4. Polytropic (n = 1.3)
The correct ascending order of the work ouput in these four processes is.
(a) 1, 2, 4, 3 (b) 1, 4, 3, 2
(c) 4, 1, 3, 2 (d) 3, 4, 1, 2
www.ascentgateacademy.com Copyright : Ascent Gate Academy 9
THERMODYNAMICS
10. The values of heat transfer and work transfer for the four processes of a thermodynamic cycle are
given below:
Process 1234
Heat transfer(kJ) 300 0 -100 0
Work transfer(kJ) 300 250 -100 -250
The thermal efficiency and work ratio for the cycle will be respectively.
(a) 33% and 0.66 (b) 66% and 0.36
(c) 36% and 0.66 (d) 33% and 0.36
11. A gas expands from pressure P1 to pressure P2 (P2 = P1/10). If the process of expansion is
isothermal, the volume at the end of expansion is 0.55 m3. If the process of expansion is adiabatic, the
volume at the end of expansion will be closer to.
(a) 0.45 m3 (b) 0.55 m3
(c) 0.65 m3 (d) 0.28 m3
12. A tank containing air is stirred by a paddle wheel. The work input to the paddle wheel is 9000 kJ and
the heat transferred to the surroundings from the tank is 3000 kJ. The external work done by the
system is.
(a) zero (b) 3000 kJ (c) 6000 kJ (d) 9000 kJ
13. A 100 W electric bulb was switched on in a 2.5 m x 3m x 3m size thermally insulated room having a
temperature of 200C. The room temperature at the end of 24 hours will be [GATE-ME-06]
a) 3210C b) 3410C c) 4500C d) 4700C
14. A frictionless piston-cylinder device contains a gas initially at 0.8 MPa and 0.015 m3. It expands
quasi-statically at constant temperature to a final volume of 0.030m3. The work output (in kj) during
this process will be [GATE-ME-09]
a) 8.32 b) 12.00 c) 554.67 d) 8320.00
15. A mono-atomic ideal gas ( = 1.67, molecualr weight = 40) is compressed adiabatically from
0.1 MPa, 300 K to 0.2 MPa. The universal gas constant is 8.314 kj kmol-1K-1. The work of
compression of the gas (in KJ) is [GATE-ME-10]
a) 29.7 b) 19.9 c) 13.3 d) 0
16. The contents of a well-insulated tank are heated by a resistor of 23 in which 10A 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 engery (U) during the process in kW are [GATE-ME-11]
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
17 A pump handling a liquid raises its pressure from 1 bar to 30 bar. Take the density of the liquid as
990 kg/m3. The isentropic specific work done by the pump in kJ/kg is [GATE-ME-11]
a) 0.10 b) 0.30 c) 2.50 d) 2.93
www.ascentgateacademy.com Copyright : Ascent Gate Academy 10
THERMODYNAMICS
18. Agas expands in a frictionless 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 0.01m3. The maximum
amount of work that could be utilized from the above process is. (G-08)
(a) 0 kJ (b) 1 kJ (c) 2 kJ (d) 3 kJ
19. In a steady state steady flow process taking place in device with a single inlet and a single outlet, the
work done per unit mass flow rate is given by w = - outlet vdp, where v is the specific volume and
inlet
p is the pressure. The
expression for w given above [GATE-ME-08]
a) is valid only if the process is both reversible and adiabatic
b) is valid only if the process is both reversible and isothernal
c) is valid for any rev. process
d) is incorerrect, it must be w = outlet pdv
inlet
20. Nitrogen at an initial state of 10 barm 1m3 and 300 K is expanded isothermally to a final volume of
2m3, v = RT , where [GATE-ME-05]
a
The p-v-T relation is p + v2
a > 0, The final pressure
a) will be slightly less than 5 bar b) will be slightly more than 5 bar
c) will be exactly 5 bar
d) cannot be ascertained in the absence of the value of a
21. A vertical cylinder with a freely floating piston contains 0.1 kg air at 1.2 bar and a
small electrical resistor. The resistor is wired to an external 12 Volt battery. When a m = 0.1 kg
current of 1.5 amps is passed through the resistor for 90 secs, the piston sweeps a
(
(
(
volume 0.01 m3. Assume (i) piston and the cylinder are insulated and (ii) air behaves ^
as a ideal gas with Cv = 700 J/kg K. Find the rise in temperature of air. [GATE-ME-93] I I
22. A 2 kW, 40 litre water heater is switched on for 20 min. The heat capacity Cp for water is
4.2kJ / kg K.Assuming all the electrical energy has gone into heating the water, increase of the water
temperature oC is. (G- 2003)
(a) 2.7 (b) 4.0 (c) 14.3 (d) 25. 25
23. A perfect gas at 27.c was heated until its volume was doubled using the following three different
processes separately:
(a) Constant pressure process. (b) Isothermal process (c) Isentropic process
Which one of the following is the correct sequence inthe order of increasing value of the final
temperature of the gas reached by using the above three different processes?
(a) 1-2-3 (b) 2-3-1 (c) 3-2-1 (d) 3-1-2.
***************************
www.ascentgateacademy.com Copyright : Ascent Gate Academy 11
THERMODYNAMICS
2 WORK & HEAT
(PRACTICE QUESTIONS)
1. In which one of the following working substances. does the relation T2/T1 = (p2/p1)0. 286 hold if the
process takes place with zero heat transfer ?
(a) Wet steam (b) isentropic (c) Petrol vapour and air mixture (d) Air
2. Assertion (A):Athermodynamic system may be considered as a quantity of working substance with
which interaction of heat and work are studied.
Reason (R) : Energy in the form of work and heat aremutually convertible.
(a) BothAand R are individually true and R is the correct explanation ofA.
(b) Both A and R are true but R is not the correct explanation of A.
(c) Ais true but R is false.
(d) Ais false but R is true.
3. The work done in compressing a gas isothermally is given by:
- 1
( ) P2 -1 (b) mRT1 loge P2/P1.
(a) - 1 P1V1 P1
(c) mcp (T2-T1) kJ ( )(d) mRT1 1- T2 kJ
T1
4. The Heat transfer, Q The work done W and the change in internal energy U are all zero in the case of.
(a)Arigid vessel containing steam at 150oC left in the atmosphere which is at 25oC.
(b) 1 Kg of gas contained in an insulated cylinder expanding as the piston moves slowly outwards.
(c) a rigid vessel containing ammonia gas connectedthrough a value to an evacuated rigid vessel well
insulated &
valve being, the vessel, the value and the connecting pipes being opened and after a time, condition
through the two vessel becoming uniform.
(d) 1 Kg of air flowing adiabatically from the atmosphere into a previously evacuated bottle.
5. A tank containing air is stirred by a paddle wheel. The work input to the paddle wheel is 9000 kJand
the heat transferred to the surrounding from the tank is 3000 kJ. The external work done by the
system is.
(a) zero (b) 3000 kJ (c) 6000 kJ (d) 9000 kJ
6. Match list - I (Process) with list - II (characteristic) and select the correct answer.
List - I List - II
A. Throttling process - 1. No work done
B. Isentropic process - 2. No change in entropy
C. Free expansion - 3. Constant internal energy
D. Isothermal process - 4. Constant enthalpy
www.ascentgateacademy.com Copyright : Ascent Gate Academy 12
THERMODYNAMICS
Codes:
ABCD
(a) 4 2 1 3
(b) 1 2 4 3
(c) 4 3 1 2
(d) 1 3 4 2
7. Assertion (A) : In thermodynamic analysis, the concept of reversibility is that, a reversible process in
the most efficient process.
Reasons (R) : The energy transfer as heat and work
during the forward process,is always identically equal to the energy transfer is heat and work, during
the reversal of the process.
(a) BothAand R are individually true and R is the correct explanation ofA.
(b) Both A and R are true but R is not the correct explanation of A.
(c) Ais true but R is false.
(d) Ais false but R is true.
8. The heat absorbed or rejected during a polytropic process is equal to.
( )- n 1 / 2 ( )(b) - n x work done
n- 1
(a) - 1 x work done
( )- n x work done ( )- n 2
(c) - 1 (d) n- 1 x work done
9. Assertion (A) : Specific heat at constant pressure for anideal gas is always greater than the specific
heat at constant volume.
Reason (R) : Heat added at constant volume is not utilized for doing any external work.
(a) BothAand R are individually true and R is the correct explanation ofA.
(b) Both A and R are true but R is not the correct explanation of A.
(c) Ais true but R is false.
(d) Ais false but R is true.
10. Identity the process for which the two integrals pdv and - vdp, evaluated between any two given
states given the same value.
(a) isenthalpic (b) isothermal (c) isentropic (d) Polytropic
11. Which one of the following phenomenon occurs when gas in a piston cylinder assembly expands
reversibly at constant pressure?
(a) Heat is added to the gas (b) Heat is removed from the gas
(c) Gas does work from its own stored energy. (d) Gas undergoes adiabatic expansion.
12. Which one of the following thermodynamic processes approximates the steaming of food in a pressure
cooker?
(a) Isenthalpic (b) Isobaric (c) Isochoric (d) Isothermal
www.ascentgateacademy.com Copyright : Ascent Gate Academy 13
THERMODYNAMICS
13.
A
B
PD
C
v
Consider the four processes A,B,C and D shown in the graph given above:
Match list I (Processes shown in the graph) with list II (Index ‘n’ in the equation pvn = const.) and
select the correct answer using the code given below the lists:
List - I List - II
A. A 1. 0
B. B 2. 1
C. C 3. 1.4
D. D 4.
Codes:
ABCD
(a) 4 2 3 1
(b) 1 2 3 4
(c) 1 3 2 4
(d) 4 3 2 1
14. An ideal gas at 27o C is heated at constant pressure till its volume becomes three times. What would
be then the temperature of gas ?
(a) 81oC (b) 627oC (c) 543oC (d) 327oC
15. List- I List- II (G - 98)
(a) Heat to work - (1) Nozzle
(b) Heat to lift weight - (2) Endothermic chemical reaction
(c) Heat to strain energy - (3) Heat engine
(d) Heat to electromagnetic energy - (4) Hot air balloon / evaporation
- (5) Thermal radiation.
- (6) Bimetallic strips
16. An isolated thermodynamic system executes a process. Choose the correct statement (s) from the
following. (G - 99)
(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 with in thesystem.
www.ascentgateacademy.com Copyright : Ascent Gate Academy 14
THERMODYNAMICS
17. A reversible thermodynamic cycle cootaining only three processes and producing work is to be
constructed. the constraints are. (G-05)
(i) there must be one isothermal process.
(ii) there must be one isentropic process.
(iii) the maximum and minimum cycle pressures and the clearance volume are fixed, and.
(iv) polytropic process are not allowed, then thenumber of possibles cycles are.
(a) 1 (b) 2 (c) 3 (d) 4
18. A compressor undergoes a reversible, stady flow process, The gas at inlet and outlet of the
compressor is designated as state I and state 2 respectively. Potential and kinetic v = specific
volume and P = pressure of the
gas.The specific work required to be supplied to the compressor for this gas compression process
is [GATE-ME-09]
a) Pdv
b) vdP
c) v1(P2-P1)
d) -P2(v1-v2)
19. Heat and work are [GATE-ME-11]
a) intensive properties b) extensive properties
c) point functions d) path functions
20. When a system is taken from state a to state b as shown in fig. below along path acb 74 kJ of heat
flows into the system and the system does 34 kJ of work. The amount of heat exchanged by the
system along path adb, if work done is 8.5 kJ will be.
c b
p
ad
v
(a) -48.5 kJ (b) 48.5 kJ (c) 31.5 kJ (d) -31.5 kJ
(d) 2251 kJ
21.
p,bar 50 A B pv1. 3 = C
0.2 0.4 C
0.8
The total work done by is V,m3
(a) 700 kJ (b) 300 MJ (c) 2952 kJ
www.ascentgateacademy.com Copyright : Ascent Gate Academy 15
THERMODYNAMICS
22. Match list - I with list - II & select the correct answer using the codes given below the lists:
List - I List - II
A. Mechanical work - 1. Low grade energy
B. Heat - 2. Concept of temperature
C. 0 - 3. High grade energy
D. Zeroth law - 4. Clausius ineqality
Codes:
ABCD
(a) 3 1 2 4
(b) 3 1 4 2
(c) 1 3 4 2
(d) 1 3 2 4
23. Given below is the table
Process Q(kJ/min) W(kJ/min) E(kJ/min)
2,000 (A)
a-b 0 0 (B)
(C)
b-c 20,000 -18,000
c-a - 2000
Select the correct values from below :
(a) A = 2000, B = -32000, C = 20000
(b) A = 2000, B = 32000, C = 16000
(c) A = -2000, B = 20000, C = 16000
(d) A = -2000, B = 20000, C = 20000
24. Consider as a system the gas contained in the cylinder as shown
in the fig below which is fitted with a piston on which a number of
small weights are placed. The initial pressure is 200 kPa and the Gas
initial volume is 0.04 m3. The gas in the cylinder is heated and the
(d) 5.88 kJ
weights be removed at such a note that the expression
pV1.5 = constant describes the relation between pressure and
volume during the process. The final volume is 0.1m3.
The work done is.
(a) 9 kJ (b) 7.3 kJ (c) 8.2 kJ
25. In a piston - cylinder arrangement the non-flow reversible process is given by v = 200 /p m3,
where P is in bar .
What will be work done when pressure increases from 1 bar to 10 bar.
(a) 4.6052 x 107 J (b) - 4.6052 x 107 J (c) 2.6052 x 107 J (d) - 2.6052 x 107 J
www.ascentgateacademy.com Copyright : Ascent Gate Academy 16
THERMODYNAMICS
26. Consider the diagram given below.
Partitions
Gas
Vaccum
The partition are removed slowly one by one slowly such the process can be consider quasistatic,
they the work done is.
(a) pdv (b) - pdv (c) zero (d) interminable
27. If a gas of volume 6000 cm3 and at a pressure of 100kPa is compressed according to
PV2= constant untill the volume becomes 2000 cm3, determine the work done during the process.
(a) -1.2 kJ (b) 1.2 kJ (c) 2.8 kJ (d) -2.8 kJ
28. Match List - I and List - II and select the correct answer
List - I List - II
A. Work done in a polytropic process 1. - vdp
B. Work done in steady flow process 2. zero
C. Heat transfer in a reversible adiabatic 3. Process.
D. Work done in isentropic process 4. P1V1 - P2V2
-1
Codes: P1V1 - P2V2
ABCD n-1
(a) 4 1 3 2
(b) 1 4 2 3
(c) 4 1 2 3
(d) 1 2 3 4
29. Consider the two diagram given below.
System boundary
ooooooo
a Gas +-
ooooooo Battery
Surrounding
ooooooo
b Gas +-
ooooooo Battery
www.ascentgateacademy.com Copyright : Ascent Gate Academy 17
THERMODYNAMICS
Choose the correct option;
(a) Both in (A)and (B) heat and work cross the boundary of the system.
(b) Both in (A)and (B) only heat crosses the boundary of the system.
(c) In A only heat crosses the boundary of the system and in B both heat and work cross the
boundary of the system.
(d) In B only work crosses the boundary of the system (Temperature of the surrounding is greater
than that of gas)
Common Data for Questions for 30 to 34
When a system is taken from state a to state b along path acb, 80 kJ heat flow into the system and
the system does 30 kJ of work.
30. If the system is taken from b to a along the path ba, work done on the system is 21kJ. Compute the
heat flow during the process. ^c b
(a) 71 kJ heat flow into the system
(b) 71 kJ heat flow from the system. p
(c) 29 kJ heat flow into the system ad
(d) 29 kJ heat flow from the system. >
v
31. What will be the heat flow, if the system is taken from a to b along path adb, work done by the
system during the process is 15 kJ
(a) 35 kJ (b) -35 kJ (c) 65 kJ (d) -65kJ
32. If Ua and Ud are 0 and 40kJ respectively, heat flow in the process ad would be.
(a) 52 kJ (b) -52 kJ (c) 57 kJ (d) -57 kJ
33. Compute the heat flow in the process db.
(a) 10 kJ (b) 50 kJ (c) 57 kJ (d) -57 kJ
34. What will be work done during the process bd ?
(a) zero (b) 35 kJ (c) 71 kJ (d) none of these.
35. Work done in a free expansion process is
(a) positive (b) negative (c) zero (d) maximum
36. For the expression pdv to represent the work, which of the following conditions should apply ?
(a) The system is closed one and process takes place in non-flow system.
(b) The process is non-quasi-static.
(c) The boundary of the system should not move in order that work may be transferred.
(d) If the system is open one, it should be non-reversible
37. Match list - I (Process) with list - II (Index n in pVn= constant) and select the correct answer using the
codes given below the lists:
List - I List - II
A. Adiabatic - 1. n = infinity
B. Isothermal - 2. n = Cp/Cv
C. Constant pressure - 3. n = 1
D. Constant volume - 4. n = Cp/Cv - 1
- 5. n = zero
www.ascentgateacademy.com Copyright : Ascent Gate Academy 18
THERMODYNAMICS
ABCD
(a) 2 3 5 4
(b) 2 3 5 1
(c) 3 2 1 5
(d) 2 5 3 1
38. Match list - I with list - II and select the correct answer
List - I Lis t- II
A. Work done in a polytropic process - 1. vdp
B. Work done in steady flow process - 2. zero
C. Heat transfer in a reversible adiabatic process- 3. (p1V1-p2V2) / (-1)
D. Work done in an isentropic process - - 4. (p1V1-p2V2) / (n-1)
39. The slope of log P-log Vgraph for a gas for isothermal change is m1and for adiabatic changes is m2.
If the gas is diatomic gas, then
(a) m1< m2. (b) m1> m2. (c) m1 + m2 = 1.0 (d) m1 = m2.
40. Assertion (A) : If the I.E. of a closed system decreases by 25 kJ while the system receives 30 kJ of
energy by heat transfer, the work done by the system is 55 kJ. Reason (R) : The first law energy
balance for a closed system is
(notations have their usual meaning) E = Q-W.
41. Assertion (A): In thermodynamic analysis, the concept of reversibility is that, a reversible process is
the most efficient process.Reason (R): The energy transfer as heat and work during the forward
process, is always idendically equal to the energy transfer as heat and work, during the reversal of the
process.
42. The number of degrees of freedom for a diatomic molecule.
(a) 2 (b) 3 (c) 4 (d) 5
43. The ratio Cp/Cv for a gas with n degrees of freedom is equal to :
(a) n + 1 (b) n - 1 (c) (2/n) - 1 (d) 1 + (2/n)
44. Assertion (A) : Ratio of specific heats Cp/Cv decreases with increases in temperature .
Reason (R): With increases in temperature, Cp decreases at a higher a rate than Cv.
45. A mass of 1.5 kg of air is compressed in a quasi- static process from 0.1 MPa to 0.7MPa, according
to the law PV= constant, initial density of air is 1.16kg/m3. Find the work done by the system.
(a) -377.5 kJ (b) 377.5 kJ (c) 251.6 kJ (d) -251.6 kJ
46. Zeroth Law of thermodynamics state that.
(a) Two thermodynamic systems are always in thermal equilibrium with each other.
(b) If two systems are in thermal equilibrium, then the third system will also be in thermal equilibrium.
(c) Two systems not in thermal equilibrium with a third system also not in thermal equilibrium with each
other.
(d) when two systems are in thermal equilibrium with a third system, they are in thermal equilibrium
with each other.
2. WORK & HEAT (PRACTICE QUESTIONS )ANS : 1-d, 2-b, 3-b, 4-c, 5-a, 6-a, 7-a, 8-c, 9-a, 10-b, 11-a, 12-c, 13-b,
14-b, 15-a-3 b4c6d5, 16-a,b,c 17-a, 18-b, 19-d, 20-sol, 21-d, 22-b, 23-c, 24-d, 25-b, 26-c, 27-a, 28-c, 29-c, 30-b, 31-c, 32-c,
33-a, 34-a, 35-c, 36-a, 37-b, 38-a2 b1 c2 d3, 39-a, 40-T, T, 41- T, T, 42-d, 43-d, 44-T, F, 45-d, 46-d.
www.ascentgateacademy.com Copyright : Ascent Gate Academy 19
THERMODYNAMICS
3 FIRST LAW OF THERMODYNAMICS
(CLASS WORK OBJECTIVE)
1. Hot water flows with a velocity of 0.1 m/s in a 100 m long, 0.1 m diameter pipe. heat loss from the
pipe outer wall is uniform and equal to 420 W / m2. If the inlet water temperature is 800C, calculate the
water temperature at the exit. Neglect effect of pipe wall thickness. Cp (water) = 4.2 kJ / kg 0 C and
density of water = 1000 kg / m3 .(G - 98)
2. A steel ball of mass 1 kg and specific heat 0.4 kj/kg is at a temperature of 600C . It is dropped into
1 kg water at 200C. The final steady state temperature of water is
a) 23.50C b) 300C
c) 350C d) 400C
3. What is the speed of sound in Neon gas at a temperature of 500K (Gas constant of Neon is
0.4210 kJ/kg-K) ? (GATE-ME-02)
a) 492 m/s
b) 460 m/s
c) 592 m/s
d) 543 m/s
4. A steam turbine receives steam steadily at 10 bar with an enthalpy of 3000 kJ/kg and discharges at
1 bar with an enthalpy of 2700 k J/kg. The work output is 250 kJ/kg. The changes in kinetic and
petential energies are negligible. The heat transfer from the turbine casing to the surroundings is equal
to (GATE-ME-00)
a) 0 kJ b) 50 kJ c) 50 kJ d) 250 kJ
5. The fist law of thermodynamics takes the form W = -H when applied to : [GATE-ME-93]
a)Aclosed system undergoing a reversible adiabatic process.
b)An open system undergoing an adiabatic process with negligible change in kinetic and potential
energies.
c)Aclosed system undergoing a reversible constant volume process.
d)Aclosed system undergoing a reversibel constant process
6. A ballon contained 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 aboveprocess ? (GATE-ME-08)
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 inital 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 increases.
7. A 2 kW, 40 litre water heater is switched on for 20 minutes. The heat capacity CP for water is
4.2 kj/kg k.Assuming all the electrical energy has gone into heating the water increase of the water
temperature in degree centigrade is (GATE-ME-03)
www.ascentgateacademy.com Copyright : Ascent Gate Academy 20
THERMODYNAMICS
8. A rigid, insulated tank is initially evacuated. The tank is connected with a supply Air supply line
line through whichc air (assumed to be ideal gas with constant specific heats) passes >
at 1 MPa , 3500 C. A valve connected with the supply line is opened an the tank is X Valve
charged with air until the final pressure inside the tank reaches 1 MPa. The final
temperature inside the tank. (GATE-ME-08)
a) is greater than 3500 C Tank
b) is less than 3500 C
c) is equal to 3500 C
d) may be greater than less than, or equal to 3500C , depending on the volume of the tank.
9. When a system is taken from stateA to state B along the path CB
A-C-B, 180 kJ of heat flows into the system and it does 130 kJ
Volume
of work.
How much heat will flow into the system along the pathA-D-B
if the work done by it along the path is 40 kJ ? AD
Volume
(a) 40 kJ (b) 60 kJ (c) 90 kJ (d) 135 kJ
10. In a test of a water - jacketed compressor, the shaft work required is 90 kN-m/kg of air compressed.
During compression, increase in enthalpy of air is 30 kJ/kg of air and increases in enthalpy of
circulating cooling water is 40 kJ/kg of air. The change in velocity is negligible. The amount of heat lost
to the atmosphere from the compressor per kg of air is.
(a) 20 kJ (b) 60 kJ
(c) 80 kJ (d) 120 kJ
11. The internal energy of certain system is a function of temperature alone and is given by the formula
E = 25 + 0.25 t kJ. If this system executes a process for which the work done by it per degree
temperature increase is 0.75 kN-m, the heat interaction per degree temperature increase, in kJ is .
(a) - 1.00 (b) -0.50
(c) 0.50 (d) 1.00
12. A system undergoes a process during which the heat transfer to the system per degree increase in
temperature is given by the equation:
dQ/dT = 2.0 kJ/oC. the work done by the system per degree increase in temperature is given by the
equation.
dW/dT = 2-0.1 T, where T is in oC, if during the process the temperature of water varies from 100oC
to 150oC what will be the change in internal energy ?
(a) 725 KJ (b) 625 KJ
(c) 600 KJ (d) 700 KJ
13. An insulated tank initiallycontains 0.25 kg of a gas with an internal energyof 200 kJ/kg.Additional gas
with an internal energy of 300 kJ/kg and an enthalpy of 400 kJ/kg enters the tank until the total mass
of gas contained is 1 kg. What is the final internal energy (in kJ/kg) of the gas in the tank ?
(a) 250 (b) 275
(c) 350 (d) None of the above
www.ascentgateacademy.com Copyright : Ascent Gate Academy 21
THERMODYNAMICS
14. 170 kJ of heat is supplied to a system at constant volume. Then the system rejects 180 kJ of heat at
constant pressure and 40 kJ of work si done on it. The system is finally brought to its original state by
adiabatic process. The initial value of internal energy is 100 kJ,
then which one of the following statements is correct ?
(a) The highest value of internal energy occurs at the end of the constant volume process.
(b)The highest value of internal energy occurs at the end of the constant pressure process.
(c) The highest value of internal energy occurs after adiabatic expansion.
(d) Internal energy is equal at all points.
15. 85 kJ of heat is supplied to a closed system at constant volume. During the next process, the system
rejects 90 kJ of heat at constant pressure while 20 kJ of work is done on it. The system is brought to
the original state by an adiabatic process. The initial internal energyis 100kJ. Then what is the quantity
of work transfer during the process ?
(a) 30 kJ (b) 25 kJ (c) 20 kJ (d) 15 kJ
16. The air with enthalpy of 100 kJ/kg is compressed by an air compressor to a pressure and temperature
at which its enthalpy becomes 200 kJ/kg. The loss of heat is 40 kJ/kg from the compres sor as the air
passes through it. Neglecting kinetic and Potential energies , the power required for an air mass flow
of 0.5 kg/s is.
*****************
www.ascentgateacademy.com Copyright : Ascent Gate Academy 22
THERMODYNAMICS
3 FIRST LAW OF THERMODYNAMICS
(PRACTICE QUESTIONS)
1. For a simple closed system of constant composition, the difference between the net heat and work
interactions is identifiable as the change in.
(a) Enthalpy (b) Entropy (c) Flow energy (d) Internal energy
2. Gas contained in a closed system consisting of piston cylinder arrangement is expanded . Work done
by the gas during expansion is 50 kJ. Decreases in internal energy of the gas during expansion is
30 kJ. Heat transfer during the process is equal to.
(a) -20 kJ (b) + 20 kJ (c) - 80 kJ (d) + 80 kJ
3. Change in internal energy in a reversible process occuring in a closed system is equal to the heat
transferred if the process occurs at constant :
(a) Pressure (b) Volume (c) Temperature (d) Enthalpy
4. In a polytropic process, the term is equal to:
(a) Heat absorbed or rejected (b) Change in internal energy
(c) Ratio of T1 / T2 (d) Work done during polytropic expansion .
5. A closed system undergoes a process 1-2 for which the values of Q1-2 and W1-2 are + 20 kJ and +
50 kJ, respectively. If the system is returned to state, 1, and Q2-1 is -10 kJ, what is the value of the
work W2 -1.
(a) + 20 kJ (b) - 40 kJ (c) - 80 kJ (d) + 40 kJ
6. A gas is compressed in a cylinder bya movable piston to a volume one-half of its original volume.During
the process, 300 kJ heat left the gas and the internal energy remained same. What is the work done
on the gas ?
(a) 100 kNm (b) 150 kNm (c) 200 kNm (d) 300 kNm
7 Assertion (A): The internal energy depends on the internal state of a body, as determined by its
temperature, pressure and composition .
Reason (R) : Internal energy of a substance does not include any energy that it may possess as a result
of its macroscopic position or movement.
(a) BothAand R are individually true and R is the correct explanation ofA.
(b) Both A and R are true but R is not the correct explanation of A.
(c) Ais true but R is false.
(d) Ais false but R is true.
8. Assertion (A): Though heat is added during a polytropic expansion process for which > n > 1, the
temperature of the gas decreases during the process.
Reason (R) : The work done by the system exceeds the heat added to the system.
(a) BothAand R are individually true and R is the correct explanation ofA.
(b) Both A and R are true but R is not the correct explanation of A.
(c) Ais true but R is false.
(d) Ais false but R is true.
www.ascentgateacademy.com Copyright : Ascent Gate Academy 23
THERMODYNAMICS
9. Which one of the following is correct ?
The cyclic integral of (d - aw) for a process is .
(a) positive (b) negative (c) zero (d) unpredictable
10. A fluid flowing along a pipe line undergoes a throttling process from 10 bar to 1 bar is passing through
a partiallyopen valve. Before throttling, the specific volume of the fluid is 0.5 m3/kg and after throttling
is 2.0m3/kg. What is the change in specific internal energy during the throttling process?
(a) zero (b) 100 kJ/kg (c) 200 kJ/kg (d) 300 kJ/kg
11. In which one of the following processes, in a closed system the thermal energy transferred toa gas is
completely converted to internal energy resulting in an increase in gas temperature ?
(a) isochoric process (b) Adiabatic process (c) Isothermal process (d) Free expansion
12. In a throttling process, which one of the following parameters remains constant ?
(a) temperature (b) pressure (c) enthalpy (d) entropy
Common Data for Question No. 13 to 15
One kg of ideal gas is heated from 180C to 930C. Assuming R = 0.264 kJ / kgk and g = 1.18 for the
gas and heat transfer is 160 kJ.
13. Cp and Cv are
(a) 1.005 kJ / kgk, 0.718 kJ/kgk
(b) 1.062 kJ / kgk, 0.798 kJ/kgk
(c) 1.005 kJ / kgk, 0.287 kJ/kgk
(d) 1.731 kJ / kgk, 1.467 kJ/kgk.
14. Change in internal energy of the system is.
(a) 170 kJ/kg (b) 110 kJ/kg (c) 85 kJ/kg (d) 78 kJ/kg.
15. Work done by the system is.
(a) 78 kJ (b) 110 kJ (c) 50 kJ (d) 98 kJ
Common Data for Question No. 16 to 17
Air flows steadily at the rate of 0.5 kg/s through an air compressor, entering at 7m/sec velocity,
100 kPa pressure and 0.95m3 / kg volume and leaving at 5m/sec 700 kPa and 0.19m3/kg. The internal
energy leaving air is 90kJ/kg greater than that of the air entering. Cooling water in the compressor
jacket absorbs heat from the air at the rate of 58 kW.
16.. Determine the ratio of the inlet pipe diameter to outlet pipe diameter.
(a) 3.21 (b) 2.22 (c) 2.09 (d) 1.89=
17. Compute the rate of shaft work input.
(a) 68 kW (b) 108 kW (c) 122 kW (d) none.
18. Airs enters a reciprocating compressor at 2 x 105 Pa and 270C having a specific volume of 1.8 m3 / kg
adn it is compressed to 6 x 105 Pa isothermally. For this system.
(a) Work is done on the system and heat is added to system and is equal to 359.5 kJ / kg.
(b) Work is done on the system and heat is rejected by the system and is equal to 395.5 kJ/ kg.
(c) Work is done by the system and heat is rejected by the system and is equal to 359.5 kJ / kg.
(d) Work is done by the system and heat is rejected by the system and is equal to 395.5 kJ / kg.
www.ascentgateacademy.com Copyright : Ascent Gate Academy 24
THERMODYNAMICS
Common Data for Question 19 to 20.
If the specific heat capacity of the gas is given as:
Cv = (0.4 + 0.004t) kJ/kg -0C.if 6 kg of a gas is heated in a container from 25 to 1250C.
19. Compute the heat transfer.
(a) 210 kJ (b) 220 kJ (c) 380 kJ (d) 420 kJ.
20. What would be net change in I.E ?
(a) 210 kg (b) 220 kJ (c) 380 kJ (d) 420 kJ.
21. A system undergoes a change of state during which 120 kJ fo heat is transferred to it and it does 80 kJ
of work. The system is brought back to original state through a process during which 80 kJ of heat
flows from the system. The work done.
(a) on the system is 10 kJ (b) by the system is 10 kJ
(c) on the system is 150 kJ (d) none of the above.
22. Match the list
(a) Internal energy (i) Heat supplied at constant volume
(b) Enthalpy (ii) High grade energy
(c) Mechanical work (iii) Heat supplied at constant pressure
(d) Open system (iv) Thermal flask
(v) Compressor
23. A pump forces 1 m3/min of water horizontally from an open well to a closed tank where pressure is
0.9 MPa. The work the pump must do upon water in per second just to force the water into tank
against the pressure is.
(a) 900 kJ (b) 79.86 kJ (c) 10.3 kJ (d) 13.31 kJ
******************
“Only he who can see the invisible can do the impossible”
3. FIRST LAW OF THERMODYNAMICS (PRACTICE QUESTIONS)Ans :
1-d, 2-b, 3-b, 4-a, 5-b, 6-d, 7-a, 8-a, 9-c, 10-d, 11-a, 12-c, 13-d, 14-b, 15-c, 16-d, 17-c, 18-b, 19-
d, 20-d, 21-a, 22-sol, 23-d,
www.ascentgateacademy.com Copyright : Ascent Gate Academy 25
THERMODYNAMICS
4 SECOND LAW OF THERMODYNAMICS
(CLASS WORK OBJECTIVE)
1. A solar energy based heat engine which recieves 80 kJ of heat at 100 o C and rejects 70 kJ of heat
to the ambient at 0o C is be designed. The thermal efficiency of the heat engine is. (G - 96)
(a) 70 % (b) 1.88 % (c) 12.5 % (d) 55 %
2. An industrial heat pump operates between the temperatures of 27°C and 13°C. The rates of heat
addition and heat rejection are 750 W and 1000W, respectively. The COP for the heat pump is .
(G- 2003)
(a) 7.5 (b) 6.5 (c) 4.0 d) 4.5
3. A heat engine having an efficiency of 70 % is used to drive a refrigerator having a co-efficient of
performance of 5. the energy absorbed from low temperature reservoir by the refrigerator for each kJ
of energy absorbed from high temperature source by the engine is. (G- 2004)
(a) 0.14 kJ (b) 0.71 kJ (c) 3.5 kJ (d) 7.1 kJ
4. A solar collector receiving solar radiation at the rate of 0.6 kW / m2 transforms it to the internal energy
of a fluid at an overall efficiency of 50%. the fluid heated to 350 K is used to run a heat engine which
rejects heat at 313 K. if the heat engine is to deliver 2.5 kW power, then mimimum area of the solar
collector required would be (G- 2004)
(d) 79.36m2
(a) 8.33m2 (b) 16.66m2 (c) 39.68m2
5. A heat transformer is a device that transfers a part of the heat, supplied to it at an intermediate
temperature, to a high temperature reservoir while rejecting the remaining part toa low temperature
heat sink. In such a heat trans former, 100 kJ is supplied at 350 K. The maxium amount of heat in
kJ that can be transferred to 400 K, when the rest is rejected to a heat sink at 300K is. (G-07)
(a) 12.50 (b) 14.29 (c) 33.33 (d) 57.14
6. An irreversible heat engine extracts heat from a high temperature source at a rate of 100kW and
rejects heat to a sink at a rate of 50 kW. The entire work output of the heat engine is used to drive a
reversible heat pump operating between a set of independent isothermal heat reservoirs at 17°C and
75°C. The rate (in kW) at which the heat pump delivers heat to its high temperature sink is.
(G-09)
(a) 50 (b) 250 (c) 300 (d) 360
7. The following four figures have been drawn to represent a fictitious thermodynamic cycle, on the p-v
and T-s planes (GATE-ME-05)
PTP T
^^ ^^
VS VS
Figure 1 Figure 2 Figure 3 Figure 4
According to the first law of thermodynamics, equal areas are enclosed by
a) figures 1 and 2 b) figures 1 and 3 c) figures 1 and 4 d) figures 2 and 4
www.ascentgateacademy.com Copyright : Ascent Gate Academy 26
THERMODYNAMICS
8. An inventor claims that heat engine has the following specifications :
Power developed = 50 kW; Fuel burned per hour = 3 kg; Heating value of fuel = 75,000 kJ per kg;
Temperature limits = 627oC and 27oC; cost of fuel = Rs. 30/kg; Value of power = Rs. 5 / kWh The
performance of his engine is.
(a) Possible (b) not possible (c) economical (d) uneconomical
9. An electric power generating station produces 400 MW, if the coal releases 36 x 108 kJ/h of energy,
the rate of rejection of heat from the power plant is.
(a) 200 MW (b) 400 MW (c) 600 MW (d) 800 MW
10. Which of the following statements are associated with second law of thermodynaics ?
(a) When a system executes a cyclic process, net work transfer is equal to net heat transfer.
(b) It is impossible to construct an engine, that operating in a cycle will produce no other effect than
the extraction of heat from a reservoir and performance of an equivalent amount of work.
(c) It is impossible by any procedure, no matter how idealized, to reduce any system to the absolute
zero of temperature in a finite number of operations.
(d) It is impossible to construct a device that operating in a cycle will produce no effect other than
transfer of heat from a cooler to hotter body.
Select the correct answer using the codes given below:
(a) 1,2 and 4 (b) 2 and 4 (c) 2,3 and 4 (d) 2 and 3
11. A heat source H1 can supply 6000 kJ/min. at 300oC and another heat source H2 can supply 60000
kJ/min. at 100oC, which one of the following statements is correct if the surroundings are at 27oC ?
(IES-2006)
(a) Both the heat sources have the same efficiency.
(b) The first heat source has lower efficiency.
(c) The second heat source has lower efficiency.
(d) The first heat source produces higher power.
12. Aheat pump is used to heat a house in the winter and then reversed to cool the house in the summer.
The inside temperature of the house is to be maintained at 20oC. the heat transfer through the house
walls is 7.9 kJ/s and the outside temperature in winter is 5oC. What is the minimum power
(approximate) required to drive the heat pump? (IES-2006)
(a) 40.5 W (b) 405 W (c) 42.5 W (d) 425 W
13. A heat engine is supplied with 250 kJ/s of heat at a constant fixed temperature of 227oC; the heat is
rejected at 27oC, the cycle is reversible, then what amount of heat is rejected? (IES-2009)
(a) 250 kJ/s (b) 200 kJ/s (c) 180 kJ/s (d) 150 kJ/s
14. A thermal electric power plant produces 1000MW of power. If the coal releases 900 x 107 kJ/h of
energy, then what is the rate at which heat is rejected from the power plant? (IES-2009)
(a) 500 MW (b) 1000 MW (c) 1500 MW (d) 2000 MW
15. Aseries combination of two Carnot’s engines operate between the temperature of 180oC and 20oC.
If the engines produce equal amount of work, then what is the intermediate temperature ?
(a) 80oC (b) 90oC (c) 100oC (IES-2009)
(d) 110oC
www.ascentgateacademy.com Copyright : Ascent Gate Academy 27
THERMODYNAMICS
16. Two reversible engine operate between thermal reservoirs at 1200 K, T2K and 300 K such that 1st
engine receives heat from 1200K reservoir and rejects heat to thermal reservoir at T2K, while the 2nd
engine recieves heat for resvervoir at T2 K and rejects to reservoir at 300K. The efficiency of both the
engines is equalwhat is the value oftemperature T2? (IES-2004)
(a) 400 K (b) 500 K (c) 600 K (d) 700 K
17. 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. (G - 96)
(a) 50 % (b) 44 % (c) 38 % (d) 55 %
18. Which one of the following changes / sets of changes in the source and sink temperature (T1 and T2
respectively) of a reversible engine will result in the maximum improvement in efficiency?
(a) T1 + T (b) T2 - T (c) (T1 + T ) and (T2 - T) d) NOTA
19. The data given in the table refers to an engine based on Carnot cycle,
Where Q1 = Heat received (kJ/min)
Q2= Heat rejected (kJ/s)
W = Work output (kW) (IES-20001)
S.No Q1 Q2 W
1. 1500 16.80 8.20
2. 1600 17.92 8.75
3. 1700 19.03 9.30
4. 1800 20.15 9.85
If heat received by the engine is 2000 kJ/min the work output will be, nearly.
(a) 9.98 (b) 10.39 (c) 11.54 (d) 10.95
20. A heat engine receives 1000kW of heat at a constant temperature of 285oC and rejects 492 kW of
heat at 5oC.
Consider the following thermodynamic cycles in this regard. (IES-2000)
1. Carnot cycle
2. Reversible cycle
3. Irreversible cycle
Which of these cycles could possibly be executed by the engine.
(a) 1 alone (b) 3 alone (c) 1 and 2 (d) None of 1 , 2 & 3
**************
www.ascentgateacademy.com Copyright : Ascent Gate Academy 28
THERMODYNAMICS
4 SECOND LAW OF THERMODYNAMICS
(PRACTICE QUESTIONS)
1. Two blocks which are at different states are brought into contact with each other and allowed to reach
a final state of thermal equilibrium. The final temperature attained is specified by the. (IES-1998)
(a) Zeroth law of thermodynamics (b) First law of thermodynamics
(c) Second law of thermodynamics (d) Third law of thermodynamics
2 A heat pump operating on Carnot cycle pumps heat from a reservoir at 300 K to a reservoir at 600 K.
The coefficient of performance is. (IES-1999)
(a) 1.5 (b) 0.5 (c) 2 (d) 1
3 Assertion (A): Heat cannot spontaneously pass from a colder system to a hotter system without
simultaneouslyproducing other effects in the surroundings. (IES-1999)
Reason (R): Energy does not degrade each time it flows through a finite temperature difference.
(a) BothAand R are individually true and R is the correct explanation ofA.
(b) Both A and R are true but R is not the correct explanation of A
(c) Ais true but R is false.
(d) Ais false but R is true.
4 Assertion (A): Second law of thermodynamics is called the law of degradation of energy.
Reason (R): Energy does not degrade each time it flows through a finite temperature difference.
(a) BothAand R are individually true and R is the correct explanation ofA. (IES-1999)
(b) Both A and R are true but R is not the correct explanation of A
(c) Ais true but R is false.
(d) Ais false but R is true.
5 Clausius - Clapeyron equation gives the ‘slope’ of a curve in. (IES-1999)
(a) p-v diagram (b) p-h diagram (c) p-T diagram (d) T-S diagram
6 Which one of the following sets of thermodynamic laws/relations is directlyinvolved in determining the
final properties during an adiabatic mixing process? (IES-2000)
(a) The first and second laws of thermodynamics
(b) The second law of thermodynamics and steady flow relations.
(c) Perfect gas relationship and steady flow relations.
(d) The first law of thermodynamics and perfect gas relationship.
7 Consider the following statements: (IES-2000)
1The first laws of thermodynamics is a law of conservation of energy.
2. Perpetual motion machine of the first kind converts energy into equivalent work.
3.Aclosed system does not exchange work or energy with its surroundings.
4. The second law of thermodynamics stipulates the law f conservation of energy and entropy.
Which of these statements are correct.
(a) 1 and 3 (b) 2 and 4 (c) 2,3 and 4 (d) 1 and 2
8. In a cyclic process, the net heat supplied is 50 kJ/s. The work obtained from the cycle is.
(a) less than 50 kJ/sec (b) equal to 50 kJ/sec (c) more than 50 kJ/sec (d) zero
www.ascentgateacademy.com Copyright : Ascent Gate Academy 29
THERMODYNAMICS
9. A Carnot refrigerator has a COP of 6.What is the ratio of the lower to the higher absolute
temperature ? (IES-2006)
(a) 1/6 (b) 7/8 (c) 6/7 (d) 1/7
10. A reversible heat engine receives 6 kJ of heat from thermal reservoir at temperature 800K, and 8 kJ
of heat from another thermal reservoir at temperature 600K. If it rejects heat to a third thermal
reservoir at temperature 100K, then the thermal efficiency of the engine is approximately equal to.
(IES-2002)
(a) 65% (b) 75% (c) 80% (d) 85%
11 Assertion (A): Efficiency of reversible engine operating between temperature limits T1 and T2
is maximum.
Reason (R) : Efficiency of a reversible engine is greater than that of an irreversible engine.
(IES-2002)
(a) BothAand R are individually true and R is the correct explanation ofA.
(b) Both A and R are true but R is not the correct explanation of A
(c) Ais true but R is false.
(d) Ais false but R is true.
12 A reversible engine operates between temperatures T1and T2. The energy rejected by this engine is
received by a second reversible engine at temperature T2 and recjected to a reservoir at temperature
T3. If the efficiencies of the engines are same then the relationship between T1, T2 and T3 is given by.
(IES-2002)
(a) T2 = T1 + T3 (b) T2 = T12 + T32 (c) T2 = T1T3 (d) T2 = T1 + 2T3
2 2
13 For a heat engine operating on the Carnot cycle, the work output is 1/4th of the heat transferred to the
sink. The efficiencyof the engine is. (IES-2003)
(a) 20% (b) 33.3% (c) 40% (d) 50%
14 In a heat engine operating in a cycle between a source temperature of 606oC and a sink temperature
of 20oC, what will be the least rate of heat rejection per kW net output of the engine? (IES-2004)
(a) 0.50 kW (b) 0.667 kW (c) 1.5 kW (d) 0.0341 kW
15. A heat engine with 30% efficiency drives a refrigerator of C.O.P. 5.0. What would be the net heat
input to the engine for each MW of heat removed in the refrigerator ? (IES-2004)
(a) 66.67 kJ (b) 600 kJ (c) 666.67 kJ (d) 6600 kJ
16. A Carnot engine operates beteween 27oC and 327oC. If the engine produces 300 kJ of work, what
is the entropy change during heat addition ? (IES-2005)
(a) 0.5 kJ/K (b) 1.0 kJ/K (c) 1.5 kJ/K (d) 2.0 kJ/K
17. A reversed Carnot cycle working as a heat pump has a COP of 7. What is the ratio of minimum to
maximum absolute temperature. (IES-2005)
(a) 7/8 (b) 1/6 (c) 6/7 (d) 1/7
18. A refrigerator based on reversed Carnot cycle works between two such temperatures that the ratio
between the low and high temperature is 0.8. If a heat pump is operated between same temperature
range, then what would be its COP? (IES-2005)
(a) 2 (b) 3 (c) 4 (d) 5
www.ascentgateacademy.com Copyright : Ascent Gate Academy 30
THERMODYNAMICS
19. A reversible heat engine rejects 50% of the heat supplied during a cycle of operation. If this engine is
reversed and operates as a heat pump, then what is its coefficient of performance? (IES-2009)
(a) 1.0 (b) 1.5 (c) 2.0 (d) 2.5
Common Data for Question 20 to 24.
Two reversible heat engine Aand B are arranged in series.Ais rejecting heat directly to B. EngineA
recieves 200 kJ at a temperature of 421oC from a hot source, while engine B is in communication with
a cold sink at a temperature of 4.4oC; the work output ofA is twice that of B.
20. Heat rejected to cold sink is.
(a) 40 kJ (b) 60 kJ (c) 80 kJ (d) 100 kJ
21. Intermediate temperature between two engines is.
(a) 123.2oC (b) 143.4oC (c) 167.1oC (d) 178oC
22. Efficiencypf engine B is.
(a) 33.3% (b) 50 % (c) 40% (d) 47%
23. Heat received by engine B is.
(a) 60 kJ (b) 80 kJ (c) 100 kJ (d) 120 kJ
24. Efficiency engineAis.
(a) 33.3% (b) 50 % (c) 40% (d) 47%
25. 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. (G- 2001)
2 1 1 (d) 66 2 kJ
(a) 16 3 kJ (b) 33 3 kJ (c) 37 2 kJ 3
26. A carnot cycle is having an efficiency of 0.75. if the temperature of the high temperature reservoir is
727oC, what is the temperature of low temperature reservoir ? (G- 2002)
(a) 23oC (b) -23oC (c) 0oC (d) 250oC.
27. Acondenser of a refrigeration system rejects heat at a rate of 120 kW, while its compressor consumes
a power of 30 kw. The coefficient of performance of the system would be (GATE-ME-92)
a) 1/4 b) 4 c) 1/3 d) 3
28. A heat engine working on Carnot cycle receives heat at the rate of 40 kW from a source at 1200 K
and rejects it to a sink at 300 K. The heat rejected is.
(a) 30 kW (b) 20 kW (c) 10 kW (d) 5 kW
29. A reversible engine operates between temp. 900 K & T2 (T2 < 900K), & another revesible engine
between T2 & 400K (T2>400K) in series . What is the value of T2 if work outputs of both the
engines are equal ? (IES-2005)
(a) 600 K (b) 625 K (c) 650 K (d) 675 K
30. The efficiency of a Carnot engine is given as 0.75. If the cycle direction is reversed, what will be the
value of C.O.P. for the Carnot refrigerator ?
(a) 0.27 (b) 0.33 (c) 1.27 (d) 2.33
**************************
4. Second Law of Thermodynamics (Practice Questions) Ans. :
1-b, 2-c, 3-c, 4-c, 5-c, 6-d, 7-d, 8-b, 9-c, 10-d, 11-a, 12-c, 13-a, 14-a, 15-c, 16-b, 17-c, 18-d,
19-sol, 20-c, 21-b, 22-a, 23-d, 24-c, 25-a, 26-b, 27-d, 28-c, 29-c, 30-b
www.ascentgateacademy.com Copyright : Ascent Gate Academy 31
THERMODYNAMICS
5 ENTROPY
(CLASS WORK OBJECTIVE)
1. One kilomole of an ideal gas is throttled from an initial pressure of 0.5 MPa to 0.1MPa . the initial
temperature is 300 K. the entropy change of the universe is. (G - 95)
(a) 13.38 kJ / K (b) 401.3 kJ / K (c) 0.0446 kJ / K (d) -0.0446 kJ / K.
2. A system undergoes a state change from 1 to 2. According to second law of themodynamics for the
process to be feasible, the entropy change, S2- S1 of the system. (G - 97)
(a) is positive or zero (b) is negative or zero
(c) is zero (d) can be positive, negative or zero
3. A steel bar of mass 1kg and specific heat 0.4 kJ / kg is at a temperature of 600C. it is dropped into
1 kg water at 200C . The final steady state temperature of water is
(a) 23.50C (b) 300C (c) 350C (d) 400C
4. When an ideal gas with constant specific heats is throttled adiabatically, with negligible changes in
kinetic and potential energies. (G- 2K)
(a) h = 0, T = 0 (b) h >0, T = 0
(c) h > 0, S > 0 (d) h = 0, S > 0
where h,T and S represent respectively, enthalpy, temperature and entropy, temperauture and
entropy.
5. A certain mass of a pure substance undergoes an irreversible process form state 1 to state 2, the path
of the process being a straight line on the T - s diagram.
Calculate work done :-T1 = 330 K, T2 = 440 K; U1 = 170 kJ, U2 = 190 kJ; H1 = 220 kJ ,
H2 = 247 kJ, and S1 = 0.23 kJ / K, and S2 = 0.3 kJ / K, where T ,U, H and S represent
temperature,internal energy, enthalpy and entropy respectively. (G- 2K)
6. Considering the relationship TdS = dU + pdV between the entropy (S), internal energy (U), pressure
(p), temperature (T) and volume (V), which of the following statements is correct ? (G- 2003)
(a) It is applicable only for a reversible process
(b) For an irreversible process, TdS > dU + pdV.
(c) It is valid only for an ideal gas
(d) It is equivalent to 1 law, for a reversible process.
7. N2 gas (28) is enclosed in cyl. by a piston at the initial condition of 2 bar, 298 K & 1m3. In particular
process, the gas slowly expands under isothermal, condition untill the vol. becomes 2m3 e change
occurs with atm at 298 K. During this process.
a) The work interaction for the Nitrogen gas is. (G- 03)
(a) 200 kJ (b) 138.6 kJ (c) 2 kJ (d) - 200 kJ.
b) Entropy change of the universe will be (KJ/K)
(a) 0.465 (b) 0.0067 (c) 0 (d) -0.6711
www.ascentgateacademy.com Copyright : Ascent Gate Academy 32
THERMODYNAMICS
8 Which of the following relationships is valid only for reversible processes undergone by a closed
system of simple compressible substance (neglect changes in kinetic and potential energy ?)
(a) Q = dU + W (G-93)
(c) T ds = dU + W
(b) T dS = dU + pdV
(d) Q = dU + pdV
9. One kilogram of water at room temperature is brought into contact with a high temperature thermal
reservoir. The entropy change of the universe is (GATE-ME-10)
a) equal to entropy change of the reservoir
b) equal to entropy change of water
c) equal to zero
d) always positive
10. Consider the following two processees : (GATE-ME-10)
a. A heat source at 1200K loses 2500 kj of heat to a sink at 800 K
b. A haet source at 800 K loses 2000 KJ of heat to a sink at 500 K
Which of the following statements is true ?
a) Process I is more irreversible than process II
b) Process II is more irreversible than process I
c) Irreversibility associated in both the processes are equal
d) Both the processes are reversible
11. A cyclic device operates between thermal reservoirs, as shown in the figure. Heat is transferred to /
forms the cyclic device. It is assumed that heat transfer between each thermal reservoir and the cyclic
device takes place across negligible temperature difference. interactions between the cyclic device
and the respective thermal reservoirs that are shown in the figure are all in the form of heat transfer.
(GATE-ME-08)
The cylce device can be 1000 K 500 K 300 K
a) a reversible heat engine
b) a reversible heat pump or a reversible refrigeration
c) an irreversible heat engine 50 KJ
d) an irreversible heat pump or an irrevesible regrigerator 100 KJ Cyclic 60 KJ
device
12. A vapour absorption refrigeration system is a heat pump with three thermal reservoirs as shown in the
figure.Aregrigeration effect of 100 W is required at 250 K when the heat source available is at 400 K.
Heat rejection occurs at 300 K. The minimum value of heat required (in W) is
(GATE-ME-05)
a) 167 400 k
b) 100
300 k
c) 80 250k
d) 20
www.ascentgateacademy.com Copyright : Ascent Gate Academy 33
THERMODYNAMICS
13. When a system executes an irreversible cycle :
Q b) dS > 0 c) dS = 0 Q
a) < 0 d) > 0
T T
14. 2 moles of oxygen are mixed adiabaticallywith another 2 moles of oxygen in mixing chamber, so that
the final total pressure and temperature of the mixture become same as those of the individual
constituents at their initial states. The universal gas constant is given as R. the change in entropy due to
mixing, per mole of oxygen, is given by. (G-08)
(a) - R In 2 (b) 0 (c) R In 2 (d) R In 4
15. Which among the following relations is/are valid ONLY for reversible process undergone by a pure
substance ? (GATE-ME-93)
a) Q = dU + W b) T dS = dU + W
d) Q = p dV + dU
c) T dS = dU + p dV
16. If a closed system is undergoing an irreversible process, the entropy of the system.
(a) must increase (b) always remains constant
(c) must decrease (d) can increase, decrease or remain constant.
17. Figure below shows a reversible heat engine ER having heat interactions with three constant
temperature systems. Calculate the thermal efficiency of the heat engine. (GATE-ME-93)
T1 = 1000k T2 = 500k T1 = 300k
Q1 = 100 KJ Q2 = 50 KJ ^ Q3
ER
W
Common date question 18 & 19
In an experimental set-up, air flows between stations P and Q adiabatically. The directrion of flow
depends on the pressure and temperature conditions maintatined at P and Q
The conditions at station P are 150 kPa and 350 K. The temperature at station Q is 300 K.
The following are the properties and relations pertaining to air :
Specific heat at constant pressure, Cp 1.005 kJ/kg K;
Specific heat at constant volume Cv = 0.718 kJ/kg K;
Characteristic gas constant, R = 0.287 kj / kg K
Enthalpy h = CpT
Internal energy, u = Cv T. (GATE-ME-11)
18. If the air has to flow from station P to station Q, the maximum possible value of pressure in kPa at
stationQ is close to
a) 50 b) 87 c) 128 d) 150
19. If the pressure at station Q is 50 kPa, the change in entropy (SQ - SP) in kJ/kgK is
a) -0.155 b) 0 c) 0.160 d) 0.355
www.ascentgateacademy.com Copyright : Ascent Gate Academy 34
THERMODYNAMICS
20. An electric motor of 5 kW is subjected toa braking test for 1 hour. The heat generated by the frictional
forces. in the process is transferred to the surroundings at 20o. The resulting entropy change will be.
(a) 22.1 kJ/K (b) 30.2 kJ/K
(c) 61.4 kJ/K f (d) 82.1 kJ/K
21. A cyclic heat engine receives 600 kJ of heat from a 1000 K source and rejects 450 kJ to a 300K sink.
The quantity dQ/T and efficiency of the engine are respectively.
(a) 2.1 kJ/K and 70%
(b) - 0.9 kJ/K and 25%
(c) + 0.9 kJ/K and 70%
(d) - 2.1 kJ/K and 25%
22. 1600 kJ of energy is transferred from a heat reservoir at 800 K to another heat reservoir at 400 K.
The amount of entropy generated during the process would be.
(a) 6 kJ/k (b) 4 kJ/k (c) 2 kJ/k (d) 0
23. Match list - I with list - II and select the correct answer:
List - I
A. The entropy of a pure crystalline substance is zero at absolute zero temperature.
B. Spontaneous processes occur in a Certain direction.
C. If two bodies are in thermal equilibrium with a third body, then they are also In thermal equilibrium
with each other.
D. The law of convervation of energy.
List - II
1. First law of Thermodynamics.
2. Second law of Thermodynamics.
3. Third law of Thermodynamics.
4. Zeroth law of Thermodynamics.
Codes:
ABCD
(a) 2 3 4 1
(b) 3 2 1 4
(c) 3 2 4 1
(d) 2 3 1 4
24. Consider the following statements regarding the throttling process of wet steam:
1. The steam pressure and temperature decrease but enthalpy remains constant.
2. The steam pressure decreases, the temperatureincreases but enthalpy remains constant.
3. The entropy, specific volume, and dryness fraction increase
4. The entropy increases but the volume and dryness fration decrease.
Which of the above statements are correct ?
(a) 1 and 3 (b) 2 and 3
(c) 1 and 4 (d) 2 and 4
www.ascentgateacademy.com Copyright : Ascent Gate Academy 35
THERMODYNAMICS
25. Consider the following statements:
When a perfect gas enclosed in a cylinder piston device executes a reversible adiabatic expansion
process,
1. its entropy will increase
2. its entropy change will be zero.
3. the entropy change of the surroundings will be zero.
Of these statements
(a) 1 and 3 are correct (b) 2 alone is correct
(c) 2 and 3 are correct (d) 1 alone is correct
26. Consider the following statements:
The definition of
1. temperature is due to Zeroth law of thermodynamics
2. entropy is due first law of thermodynamics .
3. Internal energy is due to second law of thermodynamics.
4. reversibility is due to Kelvin- Planck’s statement.
Of these statements
(a) 1,2 and 3 are correct (b) 1, 3 and 4 are correct
(c) 1 alone is correct (d) 2 alone is correct
27. Entropy of a saturated liquid at 227oC is 2.6 kJ/kg K. Its latent heat of vaporization is 1800 kJ/kg;
then the entropy of saturated vapour at 227oC would be
(a) 2.88 kJ/kg K (b) 6.2 kJ/kg K (c) 7.93 kJ/kg K (d) 10.53 kJ/kg K
28. The throttling process undergone by a gas across an orifice is shown by its states in the following fig:
1 23
It can be represented on the diagram as (b)
(d)
T
(a) 1 2 3
S
(c)
www.ascentgateacademy.com Copyright : Ascent Gate Academy 36
THERMODYNAMICS
29. In which one of the following relation the entropy changewill be negative:
(a)Air expands isothermally from 6 bars to 3 bars.
(b)Air is compressed to half the volume at constant pressure.
(c) Heat is supplied to air at constant volume till the pressure becomes three folds.
(d) air expands isentropically from 6 bars to 3 bars.
***************
“School for the moon, even if you miss,
you’ll land amongst the stars..”
www.ascentgateacademy.com Copyright : Ascent Gate Academy 37
THERMODYNAMICS (1995)
5 ENTROPY
(PRACTICE QUESTIONS)
1. A cycle of pressure colume diagram is shown in the given
fig 1:
Same cycle on temperature-entropy diagram will be represented by
(a) (b)
(c) (d)
2 Match the curves in Diagram I with the curves in Diagram II and select the correct answer. Diagram
I (Process on p-v diagram) (1996)
Diagram I (Process on p - v plane) Diagram II (Process on T-s plane)
PT
A 12
3
OB O4
C
D5
VS
www.ascentgateacademy.com Copyright : Ascent Gate Academy 38
THERMODYNAMICS
Codes:
ABCD
(a) 3 2 4 5
(b) 2 3 4 5
(c) 2 3 4 1
(d) 1 4 2 3
3. When a system undergoes a process such that dQ = 0 and D S > 0, the process is .
T
(a) irreversible adiabatic (b) reversible adiabatic
(c) isothermal (d) isobaric
4. A system of 100 kg mass undergoes a process in which its specific entropy increases from
0.3 kJ/kg-K to 0.4 kJ/kg-K. At the same time, the entropy of the surrounding decreases from
80 kJ/K to 75 kJ/K. The process is:
(a) Reversible and isothermal (b) Irreversible
(c) Reversible (d) Impossible
5. For a thermodynamic cycle to be irreversible, it is necessary that.
(a) Q =0 (b) Q <0
T T
(c) Q >0 (d) Q 0
T T
6. Four process of a thermodynamic cycle are shown above Fig.1 on the T-s plane in the sequence
1-2-3-4, the corresponding correct sequence of these process in the p-V plane shown above in fig. II
will be.
(a) (C-D-A-B) (b) (C-A-B-D) (c) (A-B-C-D) (d) (B-C-D-A)
7. Assertion (A): If a graph is plotted for absolute temperature as a function of entropy, the area under
the curve would give the amount of heat supplied.
Reason (R): Entropy represents the maximum fraction of work obtainable from heat per degree drop
in temperature.
(a) BothAand R are individually true and R is the correct explanation ofA
(b) Both A and R are true but R is not the correct explanation of A.
(c) Ais true but R is false.
(d) Ais false but R is true.
www.ascentgateacademy.com Copyright : Ascent Gate Academy 39
THERMODYNAMICS
8. Assigning the basic dimensions to mass, length, time and temperature respectively as M,L,T and
(Temperature), what are the dimensions of entropy ?
(a) MLT-2. (b) ML2T-1-1.
(c) ML2T-2-1. (d) ML1T-2-1.
9. Which of the following statements is correct?
(a) The increase in entropy is obtained from a given quantity of heat transfer at a low temperature.
(b) The change in entropy may be regarded as a measure of the rate of the availability of heat for
transformation into work.
(c) The entropy represents the maximum amount of work obtainable per degree drop in temperature.
(d) All of the above.
10. The change in specific entropy of a system undergoing a reversible process is given by.
S2 - S1 = (Cp - Cv) In (v2/v1)
(a) Adiabatic process undergone by an ideal gas.
(b) isothermal process undergone by an ideal gas.
(c) Polytropic process undergone bya real gas.
(d) Isobaric phase change from liquid to vapour.
11. The relation ds = dQ/T, where s represents entropy, Q represents heat and T represents temperature
(absolute), holds good in which one of the following processes ?
(a) Reversible processes only
(b) Irreversible processes only
(c) Both reversible and irreversible processes.
12. Consider the following thermodynamic relation.
1. Tds = du + pdv 2. Tds = du - pdv
3. Tds = dh + vdp 4. Tds = dh - vdp
Which of these thermodynamic relations are correct.
(a) 1 and 3 (b) 1 and 4 (c) 2 and 3 (d) 2 and 4
13. Consider the following statements:
1. Zeroth law of thermodynamics is related to temperature.
2. Entropy is related to first law of thermodynamics.
3. Internal energy of an ideal gas is a function of temperature and pressure.
4. Van der Waals’ equation is related to an ideal gas.
Which of the above statements is / are correct ?
(a) 1 only (b) 2, 3 and 4
(c) 1 and 3 (d) 2 and 4
14. Assertion (A): An adiabatic process is always a constant entropy process.
Reason (R): In an adiabatic process there is no heat transfer.
(a) BothAand R are individually true and R is the correct explanation ofA
(b) Both A and R are true but R is not the correct explanation of A.
(c) Ais true but R is false.
(d) Ais false but R is true.
www.ascentgateacademy.com Copyright : Ascent Gate Academy 40
THERMODYNAMICS
15. Assertion (A): All constant entropy processes are
adiabatic , but all adiabatic processes are not isentropic.
Reason (R) :An adiabatic process which resists the exchange of energy to the surroundings may have
irreversibility due to friction and heat conduction .
(a) BothAand R are individually true and R is the correct explanation ofA
(b) Both A and R are true but R is not the correct explanation of A.
(c) Ais true but R is false.
(d) Ais false but R is true.
16. Two polytropic processes undergone by a perfect gas are shown below in the pressure volume
co-ordinates.
Which representation shows correctly the above processes on the temperature - entropy
coordianates ?
(a) (b)
(c) (d)
17. The slopes of constant volume and constant pressure lines in the T - s diagram are ............. and
.................. respectively.
18. A Carnot engine operates between 327C and 27C. If the engine produces 300 kJ of work. what is the
entropy change during heat addition ?
(a) 0.5 kJ/K (b) 1.0 kJ/K
(c) 1.5 kJ/K (d) 2. kJ/K
www.ascentgateacademy.com Copyright : Ascent Gate Academy 41
THERMODYNAMICS
19. Consider the following statements :
In an irreversible process.
1. entropy always increases.
2. the sum of the entropy of all the bodies taking part in a process always increases.
3. Once created, entropy cannot be destroyed.
Of these statements
(a) 1 and 2 are correct (b) 1 and 3 are correct
(c) 2 and 3 are correct (d) 1, 2 and 3 are correct
20. Which one of the following statements applicable to a perfect gas will also be true for an irreversible
process ? (symbols have the usual meanings)
(a) dQ = du + p dv (b) dQ = T ds
(c) T ds = du + p dv (d) None of the above
21. When a system undergoes a process such that dQ/T = 0 and S >0, the process is .
(a) irreversible adiabatic (b) reversible adiabatic
(c) isothermal (d) isobaric
22. If a system undergoes an irreversible adiabatic process, then (symbols have usual meanings)
(a) (dQ/T) = 0 and S > 0 (b) (dQ/T) = 0 and S = 0
(c) (dQ/T) > 0 and S = 0 (d) (dQ/T) < 0 and S < 0
23. Consider a body at temperature T and a reservoir at To as shown.
Body
T
Q
W
Q-W
TER
To
The maximum obtainable work is
(a) Wmax = Cp [(T - To) - Tln To / T] (b) Wmax = Cp [(T - To) - To In To / T]
(c) Wmax = Cp [(T + To) - To In T / To] (d) Wmax = Cp [(T - To) - To In To / T] Z
24. Consider two sub system 1 and 2 containing same fluid and having same mass m; but at Temperature
T1 and T2 (T1 > T2) enclosed in an adiabatic enclosure separate by a partition. If the partition is
removed and the fluids are allow to mix. The entropy change of process is.
(a) S = 2mc In (T1 > T2) / 2 (b) S = 2mc In (T1 + T2) / 2
T1 T2
T1 T2
(d) S = 2mc In T1 T2
(c) S = mc In (T1 + T2) / 2
(T1 + T2) / 2
T1 T2
www.ascentgateacademy.com Copyright : Ascent Gate Academy 42
THERMODYNAMICS
25. .Consider the following statements and choose thecorrect option .
A. Entropy is an intensive property
B. Entropy is an extensive property
C. Entropy of all pure substance can be assigned the value of zero at absolute zero temperature.
D. Entropy of an isolated system can decrease.
(a) B and D are wrong (b) A and D are wrong
(c) C and D are wrong (d) only B is wrong
26. Consider the following statements . In an irreversible
process .
1. Entropy always increases.
2. The sum of the entropy of all bodies taking part in a process always increases.
3. Once created, entropy cannot be destroyed. Of these statements
(a) 1 and 2 are correct (b) 1 and 3 are correct
(c) 2 and 3 are correct (d) 1, 2 & 3 are correct
27. A system of 100kg mass undergoes a process in which its specific entropy increases from
0.3 kJ/kg - k to 0.4 kJ/kg - k At the same time, the entropy of the surrounding decreases from
80kJ/k to 75 kJ/k. the process is.
(a) Reversible and isothermal (b) Irreversible
(c) Reversible (d) impossible
28. One kg of water at 273K is brought into contact wiht heat reservoir at 373K. when water is reached
373 K, the entropy of universe is in kJ/k.
(a) 1.305 (b) -0.122 (c) 1.122 (d) 0.183
29. 2 kg of water at 94oC is mixed with 3 kg of water at 10oC in an isolated system. What is change in
entropy due to mixing process ?
(a) 0.171 kJ/kg-k (b) 0.501 kJ/kg-k (c) 0.251 kJ/kg-k (d) 0.351 kJ/kg-k
30. Total enthalpy of stream at the inlet of a nozzle is 2800 kJ while static enthalpy at the exit is 2555 kJ.
What is the stream velocity at the exit if expansion is isentropic?
(a) 70 m/s (b) 245 m/s (c) 450 m/s (d) 700 m/s
31. A vessel contains 2.5m3 of N2 (perfect gas) at 10 bar and 3700K. This is cooled and brought to 8 bar
and 2900K. Calculate change in enthalpy and entropy (Cp for N2 is 1.04 (kJ/kg-K).
(a) 83.2 kJ/kg and 0.181 kJ/kg-K
(b) 83.2 kJ/kg and 0.253 kJ/kg-K
(c) -83.2 kJ/kg and -0.181 kJ/kg-K
(d) -83.2 kJ/kg and -0.253 kJ/kg-K
32. Nitrogen gas behaving as perfect gas is compressed from 1 bar , 2900K to 5 bar 2900K.Due to this
process, the change in entropy of the gas and the heat rejected are (R = 297J/kgK for N2 gas)
(a) 0.487 kJ/K and 136.8 kJ
(b) 0.478 kJ/K and 138.6 kJ
(c) 0.456 kJ/K and 132.5 kJ
(d) 0.465 kJ/K and 135.2 kJ
www.ascentgateacademy.com Copyright : Ascent Gate Academy 43
THERMODYNAMICS
33. The work done by 0.07 kg of air when expands according to PVn = constant is 7.6KJ. The
temperature of air falls from and initial value of 1050C to a final volume of 130C during the process.
The change of entropy during the process is.
(a) 0.00926 KJ/K, decrease
(b) 0.00926 KJ/K, increase
(c) 0.00629 KJ/K, decrease
(d) 0.00629 KJ/K, increase
Common Data for Question 34 to 37.
One kg of ice at - 5oC is exposed to atm, which is at 20oC. The ice melting & comes into thermal
equilibrium with atm.
34. The change in entropy of environment during the process is .
(a) -1.46 kJ/K (b) 1.46 kJ/K (c) 2.67 kJ/K (d) -2.77 kJ/K
35. Change in the entropy of environment is.
(a) -0.0949 kJ/k (b) 0.0949 kJ/k (c) -0.136 kJ/k (d) 0.136 kJ/k
36. The change in entropy of ice in complete process is .
(a) 0.127kJ/k (b) 0.296 kJ/k (c) 0.324 kJ/k (d)1.5549 kJ/k
37. The change in entropy of ice when temperature changes from -50C to 00C is.
(a) 0.0389kJ/k (b) 0.0287kJ/k (c) 0.0177kJ/k (d) none.
38. It is impossible by any procedure to reduce any system to the absolute zero of temperature in finite
number of operations is.
(a) zeroth law of thermodynamics .
(b) first law of thermodynamics.
(c) second law of thermodynamics.
(d) third law of thermodynamics.
39. Third law of thermodynamics can be proved by.
(a) it is a thermodynamics law based on observations and can not be proved.
(b) first law of thermodynamics
(c) second law of thermodynamics
(d) zeroth law of thermodynamics
40. A perfect gas at 27oC was heated until its volume was doubled using the following three different
processes separately:
1. Constant pressure process.
2. Isothermal process
3. Isentropic process
Which one of the following is the correct sequence in the order of increasing value of the final
temperature of the gas reached by using the above three different processes ?
(a) 1-2-3 (b) 2-3-1
(c) 3-2-1 (d) 3-1-2
www.ascentgateacademy.com Copyright : Ascent Gate Academy 44
THERMODYNAMICS
41. Consider the following statements:
When a perfect gas enclosed in a cylinder piston devices executes a reversible adiabatic expansion
process,
1. Its entropy will increase.
2. Its entropy change will be zero
3. The entropy change of the surroundings will be zero.
Of these statements:
(a) 1 and 3 are correct (b) 2 alone is correct
(c) 2 and 3 are correct (d) 1 alone is correct
42. Consider the following statements.
1.An adiabatic process is always reversible.
2.An isentropic process is always adiabatic and reversible.
(a) Both 1 and 2 are correct (b) 1 is correct
(c) 2 is correct (d) Both 1 and 2 are wrong
43. Entropy generation is
(a) a point function (b) a thermodynamic property
(b) depends upon the path (d) None of these
44. Entropy change in a polytropic process is given by
(a) S2 - S1 = (n - ) R In T2 (b) S2 - S1 = n - R In T2
( - 1 ) (1 - n ) T1 ( - 1 ) (1 - n ) T1
(c) S2 - S1 = ( - n ) R In T2 (d) S2 - S1 = ( - n ) R In T2
( - 1 ) (1 - n ) T1 ( - n ) T1
45. Clausius inequality is stated as
(a) Q < 0 (b) Q = 0 (c) Q/T > 0 (d) Q/T 0
****************************
“Hold fast to dreams, for if dreams die,
life is a broken winged bird that cannot fly”
5. Entropy (Practice Questionsz) Ans. :
1-b, 2-b, 3-a, 4-b, 5-b, 6-d, 7-d, 8-c, 9-a, 10-b, 11-a, 12-b, 13-a, 14-d, 15-d, 16-a, 17- more, less,
18-b, 19-d, 20-c, 21-a, 22-a, 23-sol, 24-b, 25-b, 26-d, 27-b, 28-d, 29-a, 30-d, 31-c, 32-b, 33-sol,
34-a, 35-b, 36-d, 37-a, 38-d, 39-c, 40-b, 41-c, 42-d, 43-c, 44-c, 45-d.
www.ascentgateacademy.com Copyright : Ascent Gate Academy 45
THERMODYNAMICS
6 AVAILABILITY
(CLASS WORK OBJECTIVE)
1. An iron cube at a temperature of 400 0 is dropped in to an insulated bath containing 10 kg water at
250 C. the water finally reaches a temperature. of 50 degree C at steady state. Given that the specific
heat of water is equal to 4186 J/kg K. Find the entropy changes for the iron cube and the water. is the
process irreversible? if so, why ? (G - 96)
2. 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 revervoir. The total loss in availability due to this process
is (GATE-ME-95)
3. Availability of a system at anygiven state is (GATE-ME-00)
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.
4. A steel billet of 2000 kg mass is to be cooled from 1250 K to 450 K. The heat released during this
process is to be used as a source of energy. The ambient temperature is 303 K and specific heat of
steel is 0.5 kj/kg K. The availabe energy of this billet is (GATE-ME-04)
a) 490.44 Mj b) 30.95 Mj c) 10.5 Mj d) 0.10 Mj
5. Agas expands in a frictionless 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 m3. The maximum
amount of work that could be utilized from the above process is (GATE-ME-08)
a) 0 kj b) 1 kj c) 2 kj d) 3 kj
6. At a place where the surroudings are at 1 bar, 270C, a closed rigid thermally insulated tank contains
2 kg air at 2 bar, 270C. This air is then churned for a while, by a paddle wheel connected to an external
motor. If it is given that the irreversibility of the process is 100 kJ, find the final temperature and the
increase in availability of air. Assume for air CV = 0.718 kJ/kg K (GATE-ME-97)
7. A system is supplied 5000 kJ of heat at 500 K from a source at 1000 K. The temperature of the
atmosphere is 27oC. The decrease in available energy after heat transfer will be.
(a) 1500 kJ (b) 1350 kJ
(c) 2700 kJ (d) 5400 kJ
8. When air is compressed, the enthalpy is increased from 100 to 200 kJ/kg. Heat lost during this
compression is 50 kJ/kg. Neglecting kinetic and potential energies, the power required for a mass
flow of 2 kg/s of air through the compressor will be.
(a) 300 kW (b) 200 kW
(c) 100 kW (d) 50 kW
www.ascentgateacademy.com Copyright : Ascent Gate Academy 46
THERMODYNAMICS
9. Match list - I with list - II and select the correct answer using the codes given below the lists:
List - I List - II
A. Irreversibility 1. Mechanical equivalent
B. Joule Thomson experiment. 2. Thermodynamic temp. scale
C. Joule’s experiment 3. Throttling process.
D. Reversible engines 4. loss of availability.
10. When ever a certain quantity of heat is transferred from a system.
(a) available energy increases. (b) available energy decreases.
(c) unavailable energy increases. (d) unavailable energy decreases.
11. Irreversibility is zero in case of
(a) adiabatic processes (b) isothermal processes
(c) non-flow processes (d) reversible processes
12. 10 kg of water is heated from 300 K to 350 K in an insulated tank due to churning action by a stirrer.
The ambient temperature is 300 K. In this context, match list - I with list - II and select the correct
answer:
List - I List - II
A. Enthalpy change - 1. 12.2 kJ/kg
B. Entropy change/kg - 2. 1968 kJ
C.Availability/ kg - 3. 2090 kJ
D. Loss of availability - 4. 656 J/kg-K
Codes:
ABCD
(a) 3 1 4 2
(b) 2 4 1 3
(c) 3 4 1 2
(d) 2 1 4 3
13. Which will be the loss of available energy associated with the transfer of 1000 kJ of heat from constant
temperature system 600 K to another at 400 K when the environment temperature is 300 K?
(a) 150 kJ (b) 250 kJ (c) 500 kJ (d) 700 kJ
********************
www.ascentgateacademy.com Copyright : Ascent Gate Academy 47
THERMODYNAMICS
6 AVAILABILITY
(PRACTICE QUESTIONS)
1. Consider the following statements:
1.Availabilityis generally conserved.
2.Availabilitycan either be negative or positive.
3.Availabilityis the maximum theoretical work obtainable.
4.Availability can be destroyed in irreversibilities.
Of these statements:
(a) 3 and 4 are correct (b) 1 and 2 are correct
(c) 1 and 3 are correct (d) 2 and 4 are correct
2. Neglecting changes in kinetic energy and potential energy, for until mass the availabilityan a non-flow
process becomes a = -o, where is the availability function of the
(a) Open system (b) Closed system
(c) isolated system (d) Steady flow process
3. The irreversibility is defined as the difference of the maximum useful work and actual work;
I = Wmax useful - W actual. How can this be alternatively expressed ?
(a) I = To (Ssystem + Ssurrounding) (b) I = To (Ssystem - Ssurrounding)
(c) I = To (Ssystem + Ssurrounding) (d) I = To (Ssystem + Ssurrounding)
4. Availability function for a closed system is expressed as:
(a) = u + pov - ToS (b) = du + podv - TodS
(c) = u - pov - ToS (d) = du - podv + TodS
5 For a steady flow process from state 1 to 2, enthalpy changes from h1 = 400 kJ/kg to h2 = 100 kJ/kg
and entropy changes from s1 = 1.1 kJ/kg -K to s2 = 0.7 kJ/kg -K.
Surrounding environmental temperature is 300 K neglect changes in kinetic and potential energy. The
change in availabilityof the system is.
(a) 420 kJ/kg (b) 300 kJ/kg (c) 180 kJ/kg (d) 90 kJ/kg
6. Assertion (A): The change in avaliability of a system is equal to the change in the Gibbs function of the
system at constant temperature and pressure.
Reason (R): The Gibbs function is useful when evaluating the availability of systems in which
chemical reactions occur.
(a) BothAand R are individually true and R is the correct explanation ofA
(b) Both A and R are true But R is not the correct explanation ofA
(c) Ais true but R is false (d) A is false but R is true.
7. In a certain process,which condensing at 420oC, transfers heat to water evaporating at 250oC. The
resulting heat is used in a power cycle which rejects heat at 27oC.The fraction of the available energy
in the heat transfer process at 420oC that is lost due to irreversible heat transfer at 250oC is.
(a) 0.248 (b) 0.4 (c) 0.16 (d) 0.26
www.ascentgateacademy.com Copyright : Ascent Gate Academy 48
THERMODYNAMICS
8. What will be the loss of available energy associated with the transfer of 100 kJ of heat from constant
temperature system at 600K to another at 400 K when the environment temperature is 300 K.?
(a) 150 kJ (b) 250 kJ (c) 500 kJ (d) 700 kJ
9. 25 kg of water at 95oC mix with 35 kg of water at 35oC, the pressure being taken as constant and
temperature of surrounding being 15oC.Total available energy (before mixing) is
(Cp of water = 4.2 kJ/kg - k)
(a) 1085 kJ (b) 985 kJ (c) 400 kJ (d) 685 kJ
10. Decrease in available energy due to mixing.
(a) 100 kJ (b) 200 kJ (c) 281.7 kJ (d) 300 kJ
11. Air suffers expansion in a turbine from pressure 360 KPa to 90 KPa due to which its temperature falls
from 7500K and 5500K. In the expansion process it looses 9 kJ/kg of heat to surroundings which are
at 220C. The irreversibility for the process is (For air Cp =1.005 kJ/kg oK)
(a) 43.3 kJ/kg (b) 74.5 kJ/kg (c) 91.95 kJ/kg (d) 95.4 kJ/kg
Common Data for Question No. 12 to 14
A single stage air turbine is to operate with an inlet pressure and temperature of 6 bar and 900K.
Outlet pressure and temperature are 1 bar and 600K.Ambient conditions are 1 bar and 300K. During
expansion turbine looses 20 kJ/kg to the surrounding.
12.. Calculate maximum work obtainable.
(a) 290.5 kJ (b) 313.5 kJ (c) 333.5 kJ (d) none.
13. What will be change in availability?
(a) 110 kJ (b) 85 kJ (c) 65 kJ (d) 52 kJ
14. A heat source at 1000K transfers heat at the rate of 2000kJ/s to a system at 400k. Ambient
temperature is 300k. compute the decrease in available energy after heat transfer.
(a) 600 kJ (b) 750 kJ (c) 900 kJ (d) 1050 kJ.
15. Consider the following statement
1. Higher is temperature at which the heat engine receives the higher is the unavailable energy.
2. Lower is temperature at which the heat engine receives the higher is the unavailable energy.
3. Higher is the available energy loss, when heat loss occurs at higher temperature.
(a) 1 and 3 are correct (b) only 1 is correct
(c) 2 and 3 are correct (d) only 2 is correct
********************
“It takes struggle, a goal and enthusiasm to make a champoin”
6. Availability (Practice Questions) Ans. :
1-a, 2-b, 3-a, 4-a, 5-sol, 6-b, 7-a, 8-b, 9-a, 10-c, 11-a, 12-b, 13-d, 14-c, 15-c.
www.ascentgateacademy.com Copyright : Ascent Gate Academy 49
THERMODYNAMICS
7 PROPERTIES OF PURE SUBSTANCES
(CLASS WORK OBJECTIVE)
1. Consider the phase diagram of a certain substance as shown in the fig. Match list - I (Process) with
list - II (Curves / lines) and select the correct answer using the codes given below the lists:
List - I List - II
(process) (curves / lines)
A. Vaporization - 1. FE
B. Fusion - 2. EG
C. Sublimation - 3. ED G
ABC Pressure D
E
(a) 1 3 2 F
(b) 1 2 3 Temperature
(c) 3 2 1
(d) 3 1 2
2. Number of components (C), phase (P) and degrees of freedom (F) are related by Gibbs-phase
rule is.
(a) C - P - F = 2 (b) F - C- P = 2
(c) C + F - F = 2 (d) P + F - C = 2
3. Consider the following statement:
When dry saturated steam is throttled from a higher pressure to a lower pressure, the
1. pressure decreases and the volume increases.
2. temperature decreases and the steam becomes super heated
3. temperature and the dryness fraction increase.
4. entropy increases without any change in enthalpy
Which of these statements are correct:
(a) 1 and 4 (b) 1, 2 and 4 (c) 1 and 3 (d) 2 and 4
4. A saturated vapour is compressed to half of its volume without changing its temperature. The result
is that :
(a)All the vapour condenses to liquid.
(b) Some of the liquid evaporates and the pressure does not change.
(c) The pressure is double its initial value.
(d) Some of the vapour condenses and the pressure does not change.
5. Saturated liquid at a high pressure p1, having enthalpy of saturated liquid 1000 kJ/kg si throttled to
a lower pressure p2, at pressure p2 enthalpy of saturated liquid and that of the saturated vapour are
800 and 2800 kJ/kg respectively. The dryness fraction of vapour after throttling process is.
(a) 0.1 (b) 0.5 (c) 18/28 (d) 0.8
www.ascentgateacademy.com Copyright : Ascent Gate Academy 50
The words you are searching are inside this book. To get more targeted content, please make full-text search by clicking here.
thermo objective
Discover the best professional documents and content resources in AnyFlip Document Base.
Search