In this article you will get all resources for Thermodynamics Subject for SSC JE exam like syllabus, important MCQ’s, Classes for SSC JE.
Thermodynamics Syllabus for SSC JE-
1st Law of Thermodynamics : Definition of stored energy & internal energy, 1 Law ofThermodynamics of cyclic process, Non Flow Energy Equation, Flow Energy & Definition of Enthalpy, Conditions for Steady State Steady Flow; Steady State Steady Flow Energy Equation. 2nd Law of Thermodynamics : Definition of Sink, Source Reservoir of Heat, Heat Engine, Heat Pump & Refrigerator; Thermal Efficiency of Heat Engines & co-efficient of performance of Refrigerators, Kelvin – Planck & Clausius Statements of 2nd Law of Thermodynamics, Absolute or Thermodynamic Scale of temperature, Clausius Integral, Entropy, Entropy change calculation of ideal gas processes. Carnot Cycle & Carnot Efficiency, PMM-2; definition & its impossibility.
Important Topics of Thermodynamics for SSC JE-
- First law of Thermodynamics
- Enthalpy
- Entropy
- Thermodynamics Properties
- Heat Engine, Heat Pump and Refrigerator
- 2nd Law of Thermodynamics
- Carnot cycle
Top 50 MCQ’s of Thermodynamics for SSC JE-
In this section, you will get important MCQ’s from previous year questions of SSC JE exam and also from other PSU’s exams held before.
1. In highly rarefied gases, the concept of this loses validity
(a) Stability
(b) Macroscopic viewpoint
(c) Continuum
(d) Thermodynamic equilibrium
Answer- (c) Continuum
2. Which of the following is the extensive property of a thermodynamic system?
(a) Entropy
(b) Pressure
(c) Temperature
(d) Density
Answer- Entropy
3. An insulated container is divided into two compartments A and B by a thin diaphragm. While A contains a mass of gas at pressure P and temperature T, B is evacuated. The diaphragm punctured and the gas in A rushes into B. The process is called
(a) Adiabatic
(b) Isentropic
(c) Constant internal energy
(d) Free expansion
Answer- (d) Free expansion
Expansion of gas against vacuum.
4. Consider the following properties
(1) Temperature
(2) viscosity
(3) Specific entropy
(4) Thermal conductivity
Which of the above properties of a system is/are intensive?
(a) 1 only
(b) 2 and 3
(c) 2, 3 and 4
(d) 1, 2, 3 and 4
Answer- (d) 1, 2, 3 and 4
5. In which of the following processes, the heat is fully converted into work?
(a) Reversible adiabatic process
(b) Reversible isobaric process
(c) Reversible isometric process
(d) Reversible isothermal process
Answer- (d) Reversible isothermal process
Because temperature is constant so total heat added will be converted into work.
6. Change in enthalpy in a closed system is equal to the heat transferred, if the reversible process takes place at constant
(a) Entropy
(b) Internal Energy
(c) Pressure
(d) Temperature
Answer- (c) Pressure
We know, dQ = dU + dW(Pdv) and h = u + Pv
dh = dq − p·dV + d(pV)
dh = dq − p·dV + p·dV + V·dp + dVdp
dh = dq + V·dp + dVdp
P = c
dh = dq
7. 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
Answer- (d) Internal Energy
8. A 2 KW, 40 litre water heater is switched on for 20 minutes. The heat capacity Cp for water is 4.2 KJ/KgK. Assuming all the electrical energy has gone into heating the water. The increase of the water temperature is
(a) 14.3 degree C
(b) 2.3 degree C
(c) 7.3 degree C
(d) 8.3 degree C
Answer-
Q = mCpdT = Power X Time
2 X 1200 = 2400 = ρVCpdT = 1000 X (40/1000) X 4.2 X dT
dT = 14.3 degree C
9. A gas is compressed in a cylinder by a 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. The work done on the gas is
(a) 100 KNm
(b) 200 KNm
(c) 300 KNm
(d) 350 KNm
Answer- (c) 300 KNm
dQ = dU + dW
Here dU = 0
So, dQ = dW = 300 KNm
10. Consider the following systems:
(1)An electric heater
(2)A gas turbine
(3)A reciprocating compressor
The steady flow energy equation can be applied to which of the above systems?
(a) 1 and 2 only
(b) 1 and 3 only
(c) 1, 2 and 3
(d) 2 and 3 only
Answer- (c) 1, 2 and 3
10. In a cyclic process, the heat transfer are 30 J, -50 J, -10 J and 60 J. The net work for the cycle process is
(a) 30 J
(b) 40 J
(c) 50 J
(d) 60 J
Answer- dU = 0 in case of cyclic process
Summation of Work done = Wnet
= 30 – 50 – 10 + 60
= 30 J
11. A closed gaseous system undergoes a reversible constant pressure process at 2 bar in which 100 KJ of heat is rejected and the volume changes 0.2 m^3 to 0.1 m^3. The change in the internal energy of the system is
(a) – 100 KJ
(b) – 80 KJ
(c) – 60 KJ
(d) – 40 KJ
Answer-
W = P (V2 – V1) = 2 X 10^5 X (0.1 – 0.2) = – 20 KJ
We also know,
Q = dU + W
dU = Q – W = – 100 + 20 = -80 KJ
12. The enthalpy drop for flow through convergent horizontal nozzles is 100 KJ/Kg. If the velocity of approach at inlet to the nozzle is negligible, the exit velocity of the fluid is
(a) 20 m/s
(b) 400 m/s
(c) 447.2 m/s
(d) 520.8 m/s
Answer-
(c) 447.2 m/s
Exit velocity
V2 = (2dh)^(1/2)
= (2 X 100 X 1000)^(1/2)
= 447.21 m/s
13. There is no work transfer involved in this process
(a) Adiabatic expansion
(b) Isothermal expansion
(c) Polytropic expansion
(d) Free expansion
Answer-
(d) Free expansion
14. An insulated box containing 0.5 Kg of a gas having Cv = 0.98 KJ/KgK falls from a balloon 4 Km above the earth’s surface. The temperature rise of the gas when the box hits the ground is
(a) 0 K
(b) 20 K
(c) 40 K
(d) 60 K
Answer-
In this case,
Change in potential energy = Change in internal energy
mgh = mCVdT
dT = mgh/mCv = {9.81 X 4 X 1000}/{0.98 X 10^3} = 40.04K
15. A fluid flowing along a pipe line undergoes a throttling process from 10 bar to 1 bar is passing through partially open valve. Before throttling, the specific volume of the fluid is 0.5m^3/Kg and after throttling is 2.0 m^3/Kg. The change in specific internal energy during the throttling process is
(a) Zero
(b) 100 KJ/Kg
(c) 200 KJ/Kg
(d) 300 KJ/Kg
Answer-
In this case throttling process (h1 = h2)
h = u + pv
u1 + p1v1 = u2 + p2v2
u2 – u1 = p1v1 – p2v2
= 10 X 10^5 X 0.5 – 1 X 10^5 X 2
= 300 KJ/Kg
16. Three engines A, B and C operating on Carnot cycle use working substances as Argon, Oxygen and Air respectively. Which engine will have higher efficiency?
(a) Engine A
(b) Engine B
(c) Engine C
(d) All engines have same efficiency
Answer-
(d) All engines have same efficiency
18. The COP of an ideal refrigerator is N. If the machine is operated as a heat pump between the same temperature limits, its COP will be
(a) N + 1
(b) N – 1
(c) N
(d) 2N
Answer-
(a) N + 1
19. An engine operates between temperature limits of 900 K and T2 and another between T2 and 400 K. For both to be equally efficient, the value of T2 will be
(a) 700 K
(b) 600 K
(c) 750 K
(d) 650 K
Answer-
(b) 600 K
T2 = (T1T3)^(1/2)
20. A series combination of two Carnot’s engines operates between the temperature of 180 degree C and 20 degree C. If the engines produce equal amount of work, then the intermediate temperature is
(a) 80 degree C
(b) 90 degree C
(c) 100 degree C
(d) 110 degree C
Answer-
(c) 100 degree C
T2 = (T1 + T3)/2
21. A reversible heat engine, operating on Carnot cycle, between the temperature limits of 300 K and 1000 K produces 14KW of power, If the calorific value of the fuel is 40,000 KJ/Kg. The fuel consumption will be:
(a) 1.4 Kg/hr
(b) 1.8 Kg/hr
(c) 2.0 Kg/hr
(d) 2.2 Kg/hr
Answer-
(b) 1.8 Kg/hr
Efficiency = 1- (T2/T1) = Output/Input
Output = 14 Kw
Input = 40,000 KJ/Kg = 40,000 X mass flow rate(Kg/hr)
22. A liquid of heat capacity 5 J/K in an insulated container is heated electricity from 300 K to 600 K. If In2 = 0.693, entropy generation of the universe would be
(a) 6.93 J/K
(b) 3.465 J/K
(c) 34.65 J/K
(d) 10.65 J/K
Answer-
We know,
Entropy generation = Cp In(T2/T1)
= 5 In(600/300) = 5 X 0.693 = 3.465 J/K
23. Increase in entropy of a system represents
(a) Increase in availability of energy
(b) Increase in temperature
(c) Decreases in pressure
(d) Degradation of energy
Answer-
(d) Degradation of energy
24. The continual motion of a movable device in absence of friction
(a) Violates the first law of thermodynamics
(b) Violates the 2nd law of thermodynamics
(c) Is the perpetual motion of the second kind
(d) Is the perpetual motion of the third kind
Answer-
(d) Is the perpetual motion of the third kind
25. Which of the following processes are irreversible?
(1)Heat transfer through finite temperature difference
(2)Free expansion
(3)Transfer of electricity through a resistor
(a) 1, 2 and 3
(b) 1 and 2 only
(c) 2 and 3 only
(d)1 and 3 only
Answer-
(a) 1, 2 and 3
26. Consider the following statements:
1.Free expansion of a gas
2.Slow heating of oil from a constant temperature source
3.Evaporation of water at its saturation temperature by a source at the same temperature
4.Isentropic compression of an ideal gas
Which of these processes are irreversible?
(a) 1 and 2
(b) 2 and 3
(c) 3 and 4
(d) 1 and 4
Answer-
(d) 1 and 4
27. The effects of heat transfer from a high temperature body to a low temperature body are-
(1)The energy is conserved
(2)The entropy is not conserved
(3)The availability is not conserved
Which of the above statements are correct?
(a) 1 and 2 only
(b) 1 and 3 only
(c) 2 and 3 only
(d) 1, 2 and 3 only
Answer-
(d) 1, 2 and 3 only
28. The maximum theoretical work obtainable, when a system interacts to equilibrium with a reference environment is called
(a) Entropy
(b) Enthalpy
(c) Exergy
(d) Rothalpy
Answer-
(c) Exergy
29. If the pure substance is below the triple point temperature, the solid on being heated will only
(a) Solidify or freeze
(b) liquefy
(c) Vaporise or sublimate
(d) Have its temperature increased
Answer-
(c) Vaporise or sublimate
30. With increases pressure, the latent heat of steam
(a) Remains same
(b) Increases
(c) Decreases
(d) Behaves unpredictably
Answer-
(c) Decreases
31. The INCORRECT statement about the characteristic of
critical point of a pure substance is that
(a) there is no constant temperature vaporization process
(b) it has point of inflection with zero slope
(c) the ice directly converts from solid phase to vapour phase
(d) saturate
Answer-
(c) the ice directly converts from solid phase to vapour
phase
the ice directly converts from solid phase to vapour Phase at constant pressure which is below critical point pressure.
32. At triple point of a pure substance, the number of degree of freedom is
(a) 0
(b) 1
(c) 2
(d) 3
Answer-
(a) 0
33. Which gas shows a heating effect in the Joule-Thomson experiment, while undergoing throttling process through a porous plug of cotton wool?
(a) Carbon dioxide
(b) Hydrogen
(c) Oxygen
(d)Nitrogen
Answer-
(b) Hydrogen
34. Which one of the following parameters is significant to ascertain chemical equilibrium of a system?
(a) Clapeyron relation
(b) Maxwell relation
(c) Gibbs function
(d) Helmholtz
Answer-
(c) Gibbs function
Gibbs energy (G) is also the thermodynamic potential, it is minimized when a system reaches chemical equilibrium at constant pressure & temperature.
35. The throttling of certain gases may be used for getting the refrigeration effect. The value of Joule-Thomson coefficient(μ) for such a throttling process is
(a) μ = 0
(b) μ = 1
(c) μ < 1
(d) μ > 1
Answer-
(d) μ > 1
36. Gibbs free energy G is defined as
(a) G = H – TS
(b) G = u – TS
(c) G = u + PV
(d) G = H + TS
Answer-
(a) G = H – TS
37. Consider the following thermodynamics relation
(1)TdS = du + PdV
(2)TdS = du – pdv
(3)Tds = dh + Vdp
(4)Tds = dh – Vdp
Which of these thermodynamics relations are correct?
(a) 1 and 3
(b) 1 and 4
(c) 2 and 3
(d) 2 and 4
Answer-
(b) 1 and 4
38. Clapeyron’s equation is used for finding out the
(a) Dryness fraction of steam only
(b) Entropy of superheated vapour only
(c) Specific volume at any temperature and pressure
(d) Total heat of superheated steam only
Answer-
(c) Specific volume at any temperature and pressure
(∂P/∂T)V = hfg/T(vfg)
39. The vapour pressure of a liquid at any arbitrary temperature can be estimated approximately with the help of
(a) Gibbs equation
(b) Joule-Kelvin Equation
(c) Clausius-Clapeyron equation
(d) Gibbs-Duhem equation
Answer-
(c) Clausius-Clapeyron equation
40. The difference between constant pressure specific heat Cp and constant volume specific heat CV for pure substance
(a) Approaches zero at triple point
(b) Approaches zero as the absolute temperature approaches zero
(c) Is always equal to the gas constant R
(d) Approaches zero at critical point
Answer-
(b) Approaches zero as the absolute temperature approaches zero
41. Which of the thermodynamic property is evaluated with the help of Maxwell equations from the data of other measurable properties of a system?
(a) Enthalpy
(b) Entropy
(c) Latent Heat
(d)Specific Heat
Answer- (b) Entropy
42. The thermodynamics parameters are:
(1)Temperature, (2) Specific volume, (3) Pressure, (4) Enthalpy and (5) Entropy
The Clapeyron Equation of state provides relationship between:
(a) 1 and 2
(b) 2, 3 and 4
(c) 3, 4 and 5
(d) 1, 2, 3 and 4
Answer-
(d) 1, 2, 3 and 4
43. A perfect gas contained in a cylinder is kept in vacuum. If the cylinder suddenly bursts, then the temperature of the gas
(a) Remains constant
(b) Becomes zero
(c) Increases
(d) Decreases
Answer-
During free expansion of a perfect gas no work is done and it is also need to know that no heat is supplied from outside. Therefore, there is no change in internal energy.
Hence, temperature remain constant.
44. In isothermal process, which statement is wrong
(a) Temperature is constant
(b) Internal energy is constant
(c) No exchange of energy
(d) (a) and (b) are correct
Answer-
No exchange of energy because in case of isothermal process- temperature and internal energy both are constant.
45. The specific heat of a gas in an isothermal process is
(a) Infinite
(b) Zero
(c) Negative
(d) Remains constant
Answer-
We know-
dQ= mcdT
C= dQ/mdt
Definition- It is defined as amount of heat which is required to raise the temperature of unit mass by one degree C.
Means specific heat will be infinity because here temperature is constant [because dt= 0].
For adiabatic it will be ZERO.
46. A container that suits the occurrence of an isothermal process should be made of
(a) Copper
(b) Glass
(c) Wood
(d) Cloth
Answer-
In this process temperature is constant so walls needed to be conducting so that heat will goes out once.it will not happen then temperature will not be constant.
47. In a cyclic process, work done by the system is
(a) Zero
(b) Equal to heat given to the system
(c) More than the heat given to system
(d) Independent of heat given to the system
Answer-
Here change in internal energy is equal to zero.
So,
dQ = dU + dW
Because dU = 0
dQ = dW
48. In adiabatic expansion of a gas
(a) Its pressure increases
(b) Its temperature falls
(c) Its density increases
(d) Its thermal energy increases
Answer-
In this process temperature will falls.
49. Temperature is a measurement of coldness or hotness of an object. This definition is based on
(a) Zeroth law of thermodynamics
(b) First law of thermodynamics
(c) Second law of thermodynamics
(d) Newton’s law of cooling
Answer-
Zeroth Law of thermodynamics talk about temperature.
50. A measure of the degree of disorder of a system is known as
(a) Isobaric
(b) Isotropy
(c) Enthalpy
(d) Entropy
Answer-
Entropy- Degree of randomness or disorder
Enthalpy- It tells how much heat and work was added or removed from the substance
h= u + pv
Isotropy- It is an uniformity in all orientations