Thermodynamics MCQ Set 1
1. The efficiency of a binary cycle is given by(here E=efficiency)
a) E = (1-E1)(1-E2)
b) E = 1 – (1-E1)(1-E2)
c) E = 1 / (E1-1)(E2-1)
d) none of the mentioned
Answer
Answer: b [Reason:] Here E1 is the efficiency of topping cycle and E2 is the efficiency of bottoming cycle.
2. For n cycles, overall efficiency would be
a) E = (1-E1)(1-E2)(1-E3)……(1-En) – 1
b) E = 1 / (1-E1)(1-E2)(1-E3)……(1-En)
c) E = (1-E1)(1-E2)(1-E3)……(1-En)
d) E = 1 – (1-E1)(1-E2)(1-E3)……(1-En)
Answer
Answer: d [Reason:] Hence we can say total loss = product of losses in all cycles.
3. By combining two cycles in series, we can get high combined efficiency even if the individual efficiencies are low.
a) true
b) false
Answer
Answer: a [Reason:] Such a high efficiency cannot be achieved by a single cycle.
4. How can we generate required power and required quantity of steam in a single process?
a) by modifying initial steam pressure
b) by modifying exhaust pressure
c) both of the mentioned
d) none of the mentioned
Answer
Answer: c [Reason:] We require modification in both the pressures.
5. In a back pressure turbine,
a) exhaust steam from turbine is used for process heating
b) the process heater replaces the condenser of Rankine cycle
c) exhaust pressure from turbine is the desired saturation pressure
d) all of the mentioned
Answer
Answer: d [Reason:] In a back pressure turbine we modify both initial steam pressure and exhaust pressure.
6. A cogeneration plant produces,
a) power
b) process heat
c) both power and process heat
d) none of the mentioned
Answer
Answer: c [Reason:] In cogeneration plant, both power and process heat are produced.
7. In a by-product power cycle,
a) the basic need is power produced and process steam is a by-product
b) the basic need is process steam and power produced is a by-product
c) both process steam and power is the basic need
d) both process steam and power is a by-product
Answer
Answer: b [Reason:] Here, power produced is a by-product and the basic need is process steam.
8. In a by-product power cycle, condenser losses is ____
a) high
b) low
c) zero
d) infinity
Answer
Answer: c [Reason:] In a normal steam plant, this is the biggest loss but in a by-product power cycle it is zero.
9. The fraction of energy utilized in a by-product power cycle is ____
a) very high
b) very low
c) zero
d) infinity
Answer
Answer: a [Reason:] The reason being the condenser losses is zero.
10. The power available from back pressure turbine through which the heating steam flows is very less.
a) true
b) false
Answer
Answer: a [Reason:] The reason being relatively high back pressure or maybe small heating requirement.
Thermodynamics MCQ Set 2
1. For an isolated system,
a) dS<0
b) dS>0
c) dS=0
d) none of the mentioned
Answer
Answer: b [Reason:] We have dU+pdV-TdS<0 and for isolated system, U and V are constant.
2. The entropy of an isolated system always ____ and reaches ____ when equilibrium is reached.
a) remains constant, maximum
b) decreases, minimum
c) increases, maximum
d) none of the mentioned
Answer
Answer: c [Reason:] This is because dS>0 for an isolated system.
3. Which constraints must be imposed on system to make the Helmholtz function decrease?
a) constant T and p
b) constant U and T
c) constant U and V
d) constant T and V
Answer
Answer: d [Reason:] In these constraints, the Helmholtz function decreases and becomes minimum at final equilibrium state.
4. If the constraints are constant p and T, then the Gibbs function of a system decreases.
a) true
b) false
Answer
Answer: a [Reason:] The Gibbs function becomes minimum at the final equilibrium state.
5. Which of the following statement is true?
a) a system is in equilibrium state if, when it is disturbed, it comes back to its original state
b) if there is a spontaneous change in the state, the system is not in equilibrium
c) during a spontaneous change, the entropy of system increases
d) all of the mentioned
Answer
Answer: d [Reason:] During a spontaneous change, the entropy of system increases and reaches a maximum when equilibrium is reached.
6. A system is said to be in a state of unstable equilibrium when
a) dG<0, dF<0, dS<0
b) dG<0, dF<0, dS>0
c) dG>0, dF>0, dS>0
d) dG>0, dF>0, dS<0
Answer
Answer: b [Reason:] These conditions refer to a spontaneous change which makes unstable equilibrium.
7. What is the criterion of stability?
a) dG<0, dF<0, dS<0
b) dG<0, dF<0, dS>0
c) dG>0, dF>0, dS>0
d) dG>0, dF>0, dS<0
Answer
Answer: d [Reason:] For these conditions, a system is said to be in a state of stable equilibrium.
8. For a system to be in a state of neutral equilibrium,
a) dS=dG=dF=0
b) dS=0, dG=dF<0
c) dS=0, dG=dF>0
d) none of the mentioned
Answer
Answer: a [Reason:] The thermodynamic criterion of equilibrium thus remains at constant value for all possible variations.
9. If a system is stable to small but not large disturbances, it is said to be in metastable equilibrium.
a) true
b) false
Answer
Answer: a [Reason:] This is the definition of metastable equilibrium and an example can be mixture of oxygen and hygrogen.
10. Which of the following is true for a system at equilibrium?
a) S=Smax and ∂S=0
b) F=Fmin and ∂F=0
c) G=Gmin and ∂G=0
d) all of the mentioned
Answer
Answer: d [Reason:] These are necessary but not the sufficient conditions for equilibrium.
11. For thermal stability,
a) Cv>0
b) (∂p/∂V)<0, at constant entropy
c) both of the mentioned
d) none of the mentioned
Answer
Answer: a [Reason:] Since T>0K , Cv>0 for thermal stability.
12. For mechanical stability,
a) Cv>0
b) (∂p/∂V)<0, at constant entropy
c) (∂p/∂V)<0, at constant temperature
d) all of the mentioned
Answer
Answer: c [Reason:] This is the condition for mechanical stability.
13. For total stability,
a) Cv>0
b) (∂p/∂V)<0, at constant entropy
c) (∂p/∂V)<0, at constant temperature
d) all of the mentioned
Answer
Answer: d [Reason:] All these three conditions are required for stability.
14. The third law is a fundamental law of nature and cannot be proved.
a) true
b) false
Answer
Answer: a [Reason:] The third law is not derivable from second law and cannot be proved as is the case with zeroth, first and second laws.
15. For magnetic cooling, ____ salt is used.
a) diamagnetic
b) paramagnetic
c) both of the mentioned
d) none of the mentioned
Answer
Answer: b [Reason:] A paramagnetic salt like gadolinium sulphate is used for magnetic cooling.
Thermodynamics MCQ Set 3
1. Useful work is given by
a) actual work + p(V2-V1)
b) actual work – p(V2-V1)
c) actual work + p(V2+V1)
d) none of the mentioned
Answer
Answer: b [Reason:] Useful work = actual work – work performed on the atmosphere.
2. In a steady flow system, which of the following does not change?
a) mass
b) volume
c) both of the mentioned
d) none of the mentioned
Answer
Answer: b [Reason:] The volume of the system remains constant for a steady flow system.
3. Which of the following is true?
a) in a steady flow system, no work is done on the atmosphere
b) in case of unsteady flow system, the volume of the system changes
c) both of the mentioned
d) none of the mentioned
Answer
Answer: c [Reason:] In a steady flow system, the volume of the system does not change but it changes for unsteady flow system.
4. Availability function for a closed system is given by
a) U-pV+TS
b) U+pV+TS
c) U-pV-TS
d) U+pV-TS
Answer
Answer: d [Reason:] This term comes very frequent and is considered as availability function.
5. When a system exchanges heat with a thermal energy reservoir in addition to the atmosphere, the maximum useful work
a) increases
b) decreases
c) remains constant
d) none of the mentioned
Answer
Answer: a [Reason:] The maximum useful work increases in this case.
6. When the system is in equilibrium with the surroundings, this state of the system is known as dead state.
a) true
b) false
Answer
Answer: a [Reason:] In this state, the system has pressure and temperature as that of surroundings, there is no chemical reaction mass transfer and has minimum potential energy.
7. When a system exchanges heat with a thermal energy reservoir at temperature Tr in addition to the atmosphere, the maximum useful work increases by
a) dQ(1+Tr/To)
b) dQ(1-Tr/To)
c) dQ(1+To/Tr)
d) dQ(1-To/Tr)
Answer
Answer: d [Reason:] The maximum useful work will be increased by dQ(1-To/Tr) where dQ is the heat received by the system.
8. When a system changes its state towards that of surroundings, the opportunity to produce more work
a) increases
b) decreases
c) remains constant
d) none of the mentioned
Answer
Answer: b [Reason:] More the system goes towards surroundings, lesser is the opportunity to produce more work.
9. When the system is in equilibrium with the surroundings, it must be in
a) pressure equilibrium
b) temperature equilibrium
c) chemical equilibrium
d) all of the mentioned
Answer
Answer: d [Reason:] When the system is in equilibrium with the surroundings, its pressure and temperature is Po and To and there should not be any chemical reaction or mass transfer.
10. All spontaneous processes terminate at the dead state.
a) true
b) false
Answer
Answer: a [Reason:] At dead state, the system is in equilibrium with the surroundings and hence the opportunity of producing work ceases to exist.
Thermodynamics MCQ Set 4
1. In vapour refrigeration cycle, which of the following is used for expansion?
a) expansion engine
b) throttling valve or capillary tube
c) both of the mentioned
d) none of the mentioned
Answer
Answer: b [Reason:] This is because in expansion engine, power recovery is small and hence its cost is not justified.
2. Which of the following operations occur in a vapour refrigeration cycle?
a) compression
b) cooling and condensing
c) expansion and evaporation
d) all of the mentioned
Answer
Answer: d [Reason:] These are the processes which constitute the vapour refrigeration cycle.
3. Compression can be
a) dry compression
b) wet compression
c) both of the mentioned
d) none of the mentioned
Answer
Answer: c [Reason:] Dry compression starts with saturated vapour and wet compression starts with wet vapour.
4. Wet compression is preferred over dry compression.
a) true
b) false
Answer
Answer: b [Reason:] Dry compression is always preferred.
5. Why is wet compression not preferred?
a) the liquid refrigerant can be trapped in the head of cylinder
b) this may damage the valves or cylinder head
c) liquid refrigerant can wash away the lubricating oil thus accelerating wear
d) all of the mentioned
Answer
Answer: d [Reason:] These are the reasons why dry compression is preferred over wet compression.
6. In the cooling and condensing, correct sequence of processes is
a) desuperheated->condensed->saturated liquid
b) desuperheated->saturated liquid->condensed
c) condensed->desuperheated->saturated liquid
d) saturated liquid->condensed->desuperheated
Answer
Answer: a [Reason:] This is the correct sequence of processes and heat is transferred out.
7. The expansion process is
a) isentropic
b) reversible
c) adiabatic
d) all of the mentioned
Answer
Answer: c [Reason:] The expansion process is adiabatic but not isentropic and is irreversible.
8. The evaporation process is a
a) constant volume reversible process
b) constant pressure reversible process
c) adiabatic throttling process
d) reversible adiabatic process
Answer
Answer: b [Reason:] This is the last process and it completes the cycle.
9. The evaporator produces the cooling or refrigerating effect.
a) true
b) false
Answer
Answer: a [Reason:] It absorbs heat from the surroundings by evaporation.
10. In the expansion process, which of the following remains constant?
a) work done
b) heat supplied
c) internal energy
d) enthalpy
Answer
Answer: d [Reason:] The expansion is an adiabatic throttling process in which enthalpy remains unchanged.
11. The COP of cycle is given by(Q2=heat absorbed by evaporator and Wc=work done by compressor)
a) 1- (Q2/Wc)
b) 1- (Wc/Q2)
c) Q2/Wc
d) Wc/Q2
Answer
Answer: c [Reason:] This is the COP of vapour refrigeration cycle.
12. One tonne of refrigeration is given as the rate of heat removal from surroundings equivalent to heat required for melting one tonne of ice in a day.
a) true
b) false
Answer
Answer: a [Reason:] This is the definition of “one tonne of refrigeration”.
13. Which of the following is recommended in a refrigeration cycle?
a) superheating of vapour
b) subcooling of liquid
c) both of the mentioned
d) none of the mentioned
Answer
Answer: c [Reason:] The superheating of vapour is done at evaporator outlet and subcooling of liquid occurs at condenser outlet.
14. Superheating of vapour and subcooling of liquid ____ the refrigerating effect.
a) decreases
b) increases
c) no change
d) none of the mentioned
Answer
Answer: b [Reason:] The refrigerating effect is increased by using these techniques.
15. A condenser must ____ and then ____ the compressed refrigerant.
a) superheat, evaporate
b) desuperheat, evaporate
c) superheat, condense
d) desuperheat, condense
Answer
Answer: d [Reason:] This is the function of a condenser.
Thermodynamics MCQ Set 5
1. Which of the following statement is true for a condenser?
a) it can be air-cooled or water-cooled
b) small self-contained units use water-cooled condenser
c) large installations use air-cooled condenser
d) all of the mentioned
Answer
Answer: a [Reason:] We use air-cooled condenser for small self-contained units and water-cooled condenser for large installations.
2. For an expansion device, which of the following is true?
a) it increases the pressure of refrigerant
b) it regulates the flow of refrigerant to evaporator
c) both of the mentioned
d) none of the mentioned
Answer
Answer: b [Reason:] The expansion device reduces the pressure of refrigerant.
3. Which of the following is a type of expansion device?
a) capillary tubes
b) throttle valves
c) both of the mentioned
d) none of the mentioned
Answer
Answer: c [Reason:] These are the two types of expansion devices.
4. Throttle valves are used in ____
a) small units
b) larger units
c) both of the mentioned
d) none of the mentioned
Answer
Answer: b [Reason:] They regulate the flow of refrigerant according to load on evaporator.
5. Capillary tubes are used in ____
a) small units
b) larger units
c) both of the mentioned
d) none of the mentioned
Answer
Answer: a [Reason:] In their case, id size and length are fixed, the evaporator pressure also gets fixed.
6. Types of compressor include
a) reciprocating
b) centrifugal
c) rotary
d) all of the mentioned
Answer
Answer: d [Reason:] These are the three types of compressor.
7. When volume flow rate of refrigerant is large, which compressor is used?
a) reciprocating
b) centrifugal
c) rotary
d) all of the mentioned
Answer
Answer: b [Reason:] For plants with higher capacities, centrifugal compressors are used.
8. Which of the following statement is true?
a) rotary compressors are mostly used for small units
b) reciprocating compressors are employed in plants with capacity up to 100 tonnes
c) both of the mentioned
d) none of the mentioned
Answer
Answer: c [Reason:] This is the difference in reciprocating and rotary compressors.
9. In reciprocating compressors, actual volume of gas drawn in cylinder is ____ the volume displaced by piston.
a) less than
b) more than
c) equal to
d) none of the mentioned
Answer
Answer: a [Reason:] The reason being, leakage, clearance and throttling effects.
10. The clearance volumetric efficiency is equal to
a) 1 + C + C(p2/p1)^(1/n)
b) 1 – C – C(p2/p1)^(1/n)
c) 1 – C + C(p2/p1)^(1/n)
d) 1 + C – C(p2/p1)^(1/n)
Answer
Answer: d [Reason:] Here C is the clearance and p1,p2 are pressures.
11. Plate evaporator is a common type of evaporator.
a) true
b) false
Answer
Answer: a [Reason:] In a plate evaporator, a coil is brazed on to a plate.
12. Why is multistage compression with intercooling adopted?
a) using a single stage with high pressure ratio decreases volumetric efficiency
b) high pressure ratio with dry compression gives high compressor discharge temperature
c) the refrigerant is damaged
d) all of the mentioned
Answer
Answer: d [Reason:] Because of these reasons we have to use multistage compression with intercooling.
13. The intercooler pressure is given by
a) p1*p2
b) sqrt(p1*p2)
c) (p1*p2)/(p1+p2)
d) (p1+p2)/2
Answer
Answer: b [Reason:] Here p1 is the evaporator pressure and p2 is the condenser pressure.
14. The most widely used refrigerants are
a) freon
b) genetron
c) arcton
d) all of the mentioned
Answer
Answer: d [Reason:] These are a group of halogenated hydrocarbons.
15. Why is ammonia used in food refrigeration?
a) high COP
b) low cost
c) lower energy cost
d) all of the mentioned
Answer
Answer: d [Reason:] Also ammonia can be detected easily in case of a leak.
Synopsis and Project Report
You can buy synopsis and project from distpub.com. Just visit https://distpub.com/product-category/projects/ and buy your university/institute project from distpub.com
