# Thermodynamics Test Questions Set - 1

1)   The energy of an isolated system

a. is always decreasing
b. is always constant
c. is always increasing
d. none of the above
 Answer  Explanation  Related Ques ANSWER: is always constant Explanation: The system in which both the mass as well as energy cannot be transferred between system and its surrounding is called as isolated system. As the energy can neither be transmitted nor be absorbed, the total energy of an isolated system is always constant.

2)   The term which can differentiate thermodynamics from other sciences is ____.

a. Pressure
b. Temperature
c. Mass
d. none of the above
 Answer  Explanation  Related Ques ANSWER: Temperature Explanation: Temperature plays a very important role in thermodynamics as force does in static and velocity does in dynamics. Temperature is the term through which we can differentiate between hot and cold. When two bodies are brought in physical contact with each other and one body has more temperature than other then hear transfer takes place from hot body to cold one. After some time they attain a common temperature and then they are in a thermal equilibrium. These phenomena are very important in thermodynamics.

3)   The thermodynamic work done by the system on the surrounding is considered as ____.

a. positive
b. negative
c. neutral
d. none of the above
 Answer  Explanation  Related Ques ANSWER: positive Explanation: The mechanical work is done by a force when it acts upon a body moving in the direction of the force. In thermodynamics, work transfer occurs between system and surrounding. Work is said to be done by a system when the energy is transferred from the system and it is responsible for or counted as some external mechanical change. When work is done by a system then it is taken as positive, and when work is done on the system by the surrounding then it is taken as negative. The symbol W is used for work transfer.

4)   When the heat transfer into a system is more than the work transfer out of the system, then

a. the internal energy of the system remains constant
b. the internal energy of the system decreases
c. the internal energy of the system increases
d. none of the above
 Answer  Explanation  Related Ques ANSWER: the internal energy of the system increases Explanation: When a system undergoes cycle, then the algebraic sum of all energy transfer across the boundaries is zero. But when a system undergoes a change of state in which both heat transfer and work transfer are involved, the net energy transfer is stored and collected within the system. If Q is the amount of heat transferred to the system and W is the amount of work transferred from the system during the process, then the net energy (Q – W) is stored in the system. This energy is neither heat nor work but it is called as internal energy. As the heat transfer is more that work transfer then the internal energy (ΔE) increases.Q – W = ΔE

5)   Practically heat and work are completely interchangeable forms of energy

a. True
b. False

 Answer  Explanation  Related Ques ANSWER: False Explanation: According to the first law of thermodynamics, the energies are converted from one form to another form. For example, according to Joule, based on his experiments, energy supplied to a system in a form of heat, can be completely converted into work. But this process is not possible, because we know that in thermodynamic process internal energy of a system also increases. Thus,Heat transfer – Internal energy increase – Work transferThe complete conversion of heat into work is not possible. Therefore heat and work are not completely interchangeable forms of energy.

6)   First law of thermodynamics provides

a. a statement that energy balance occurs when a system undergoes the change of state or the process
b. a statement about whether the change of state or the process is at all feasible or not
c. both a. and b.
d. none of the above
 Answer  Explanation  Related Ques ANSWER: a statement that energy balance occurs when a system undergoes the change of state or the process Explanation: The first law of thermodynamics states that the energy balance occurs when a system undergoes the change of state or the process. It states that if energy is supplied to a system in a form of heat, which can be completely converted into work energy. But practically it is not possible, because internal energy of the system also increases in the process. Thus, first law of thermodynamics does not provide information on whether the change of state or the process is feasible or not.

7)   The thermodynamic cycle in which net heat is transferred to the system and a net work is transferred from the system is called as

a. refrigeration cycle
b. heat engine cycle
c. both a. and b.
d. none of the above
 Answer  Explanation  Related Ques ANSWER: heat engine cycle Explanation: Heat engine can be considered as gas confined in a piston cylinder arrangement. Consider the following heat engine, The heat Q1 is transferred to the system and work W1 is done by the system. Then system is taken to its initial position by applying work W2 on the piston and heat Q2 is rejected from the system. This is the heat engine cycle. In heat engine cycle, a net heat is transferred to the system and a net work is transferred from the system.

8)   Which of the following is NOT the heat engine cycle

a. refrigerator
b. stem power plant
c. mass of gas confined in a cylinder and piston machine
d. none of the above
 Answer  Explanation  Related Ques ANSWER: refrigerator Explanation: In heat engine cycle, a net heat is transferred to the system and a net work is transferred from the system. In the system of mass of gas confined in a cylinder and piston machine, the heat is added to the system and work is done by the system on the piston and vice versa. In stem power plant initially the heat is added from the furnace to boiler, this stem passes through the turbine and work is done, then the stem is condensed to water in condenser and the heat is rejected from the system, and finally work is done on the system to pump the water back to the boiler. But refrigerator does not consist heat engine cycle, because in refrigerator, the work is done on the system and heat transfer takes place from the system.

9)   Efficiency of heat engine cycle is the ratio of

a. total heat input to the cycle (Qin) to net work output of the cycle (Wnet)
b. net work output of the cycle (Wnet) to total heat input to the cycle (Qin)
c. net work output of the cycle (Wnet) to heat rejected from the system (Qout)
d. none of the above
 Answer  Explanation  Related Ques ANSWER: total heat input to the cycle (Qin) to net work output of the cycle (Wnet) Explanation: In heat engine cycle, the heat is transferred to the system and work is transferred from the system. The main function of heat engine is to produce work output continuously by consuming heat energy given to the system. So the net work (Wnet) and heat supplied (Qin) to the system are taken into account. The net work output is the difference between work produces in the process and the work input required to take the system to initial state. In stem power plant, net work output is,Turbine Work (WT) – Pump Work (WP)Therefore, the efficiency of heat engine cycle is the ratio of total heat input to the cycle (Qin) to net work output of the cycle (Wnet).

10)   A thermal energy reservoir (TER) has

a. a finite heat capacity
b. an infinite heat capacity
c. a finite mass
d. none of the above
 Answer  Explanation  Related Ques ANSWER: an infinite heat capacity Explanation: A thermal energy reservoir has a capacity of absorbing or rejecting an unlimited amount of heat without considerable change in its temperature. These are the large bodies, in which the heat enters or leaves are very slow and very minute. Heat capacity is the product of mass of the body and specific heat of the body. As the thermal energy reservoirs are the large bodies, their heat capacity will be infinite.

a. can intersect with each other
b. cannot intersect with each other
c. may intersect or may not intersect
d. none of the above
 Answer  Explanation  Related Ques ANSWER: cannot intersect with each other Explanation: No explanation is available for this question!

12)   Which property of a system is constant in reversible adiabatic process?

a. pressure
b. volume
c. temperature
d. entropy
 Answer  Explanation  Related Ques ANSWER: entropy Explanation: No explanation is available for this question!

13)   Thermodynamics is the study of

a. energy
b. equilibrium
c. entropy
d. none of the above
 Answer  Explanation  Related Ques ANSWER: none of the above Explanation: No explanation is available for this question!

14)   What is the cyclic integral of dQ/T for reversible process?

a. less than zero
b. zero
c. more than zero
d. none of the above
 Answer  Explanation  Related Ques ANSWER: zero Explanation: No explanation is available for this question!

15)   What is the cyclic integral of dQ/T for irreversible process?

a. less than zero
b. zero
c. more than zero
d. none of the above
 Answer  Explanation  Related Ques ANSWER: less than zero Explanation: No explanation is available for this question!

16)   Any reversible path may be substituted by a reversible zigzag path between the same end processes such that the heat transfer during this zigzag path is equal to the heat transfer during original path. What are the processes involved in the zigzag path?

a. reversible polytropic and isobaric process
b. reversible polytropic and isothermal process
c. reversible adiabatic and isothermal processes
d. none of the above
 Answer  Explanation  Related Ques ANSWER: reversible adiabatic and isothermal processes Explanation: No explanation is available for this question!

17)   When a system is taken from state A to state B through a reversible path 1 and again the system is taken to its initial state A from B through different reversible path 2, then what will be the effect on entropy?

a. entropy increases
b. entropy decreases
c. entropy remains constant
d. none of the above
 Answer  Explanation  Related Ques ANSWER: entropy remains constant Explanation: No explanation is available for this question!

18)   What is the exergy of a system?

a. The minimum work that can be extracted from a system till it reaches thermodynamic equilibrium with its surroundings
b. The maximum work that can be extracted from a system till it reaches thermodynamic equilibrium with its surroundings
c. The maximum entropy that can be increased in a system till it reaches thermodynamic equilibrium with its surroundings
d. none of the above
 Answer  Explanation  Related Ques ANSWER: The maximum work that can be extracted from a system till it reaches thermodynamic equilibrium with its surroundings Explanation: No explanation is available for this question!

19)   What is the effect on quality of the energy when it is conserved?

a. the quality of the energy increases while conserving its quantity
b. the quality of the energy decreases while conserving its quantity
c. the quality of the energy remains same while conserving its quantity
d. none of the above
 Answer  Explanation  Related Ques ANSWER: the quality of the energy decreases while conserving its quantity Explanation: No explanation is available for this question!

20)   Which analysis/analyses is/are required to make energy conversion or energy conveying system more efficient?

a. First law or energy analysis
b. Second law or exergy analysis
c. Both a. and b.
d. None of the above
 Answer  Explanation  Related Ques ANSWER: Both a. and b. Explanation: No explanation is available for this question!

21)   What is a pure substance?

a. a homogeneous mixture of two substances of same composition
b. a substance with constant chemical composition throughout its mass
c. both a. and b.
d. none of the above
 Answer  Explanation  Related Ques ANSWER: a substance with constant chemical composition throughout its mass Explanation: No explanation is available for this question!

22)   A pure substance exists in

a. solid phase
b. liquid phase
c. gaseous phase
d. all of the above
 Answer  Explanation  Related Ques ANSWER: all of the above Explanation: No explanation is available for this question!

23)   What is a mole of a substance?

a. One mole has a mass numerically equal to half the molecular weight of the substance
b. One mole has a mass numerically equal to the molecular weight of the substance
c. One mole has a mass numerically equal to double the molecular weight of the substance
d. none of the above
 Answer  Explanation  Related Ques ANSWER: One mole has a mass numerically equal to the molecular weight of the substance Explanation: No explanation is available for this question!

24)   According to the Avogadro's law, what is the relation between volume of 1 kg mol of oxygen and volume of 1 kg mol of nitrogen, at normal pressure and temperature? (Mass of 1 kg mol of oxygen is 32 kg and mass of 1 kg mol of nitrogen is 28 kg)

a. volume of 1 kg mol of oxygen is greater than that of nitrogen
b. volume of 1 kg mol of oxygen is less than that of nitrogen
c. volume of 1 kg mol of oxygen is same as that of nitrogen
d. none of the above
 Answer  Explanation  Related Ques ANSWER: volume of 1 kg mol of oxygen is same as that of nitrogen Explanation: No explanation is available for this question!

25)   A single phase pure substance has following properties p, V, T, S, U, H, F (Helmholtz function) and G (Gibbs function). Any one in these properties may be expressed

a. as a function of the same property
b. as a function of any one other property
c. as a function of any two other properties
d. none of the above
 Answer  Explanation  Related Ques ANSWER: as a function of any two other properties Explanation: No explanation is available for this question!

26)   Joule-Kelvin effect can be carried out by

a. throttling process of gas
b. Joule-Thomson expansion of gas
c. both a. and b.
d. none of the above
 Answer  Explanation  Related Ques ANSWER: both a. and b. Explanation: No explanation is available for this question!

27)   What will be the net change in internal energy of working fluid of power cycle over the complete cycle?

a. net change in internal energy of working fluid will be positive
b. net change in internal energy of working fluid will be negative
c. no any net change in internal energy of working fluid
d. none of the above
 Answer  Explanation  Related Ques ANSWER: no any net change in internal energy of working fluid Explanation: No explanation is available for this question!

28)   What is the relation between net energy transferred to unit mass of the working fluid as heat in the power cycle and net energy transfer as work from the working fluid in the same power cycle, if the cycle works ideally?

a. net energy transferred to unit mass of the working fluid as heat in the power cycle is greater than net energy transfer as work from the working fluid in the same power cycle
b. net energy transferred to unit mass of the working fluid as heat in the power cycle is less than net energy transfer as work from the working fluid in the same power cycle
c. net energy transferred to unit mass of the working fluid as heat in the power cycle is equal to net energy transfer as work from the working fluid in the same power cycle
d. cannot say
 Answer  Explanation  Related Ques ANSWER: net energy transferred to unit mass of the working fluid as heat in the power cycle is equal to net energy transfer as work from the working fluid in the same power cycle Explanation: No explanation is available for this question!

29)   What is the formula for efficiency of vapour power cycle?

a. ηcycle = Wnet / Qin
b. ηcycle = (WT – WP) / Qin
c. ηcycle = (Qin – Qout) / Qin
d. all of the above
 Answer  Explanation  Related Ques ANSWER: all of the above Explanation: No explanation is available for this question!

30)   Which processes do the Rankine cycle contain?

a. two isothermal and two isochoric processes
b. two isentropic and two isobaric processes
c. two isentropic and two isothermal processes
d. two isothermal and two isobaric processes
 Answer  Explanation  Related Ques ANSWER: two isentropic and two isobaric processes Explanation: No explanation is available for this question!

31)   At ideal condition of vapour power cycle, reversible constant pressure heat rejection is carried out at

a. boiler
b. turbine
c. condenser
d. feed pump
 Answer  Explanation  Related Ques ANSWER: condenser Explanation: No explanation is available for this question!

32)   Which ideal process is carried out at the turbine in vapour power cycle?

c. reversible constant pressure heat addition
d. reversible constant pressure heat rejection

33)   In the T-s diagram of vapour power cycle, what is the condition of stem at the starting of turbine expansion? a. wet with dryness fraction 0.8
b. wet with dryness fraction 0.99
c. dry saturated
d. superheated
 Answer  Explanation  Related Ques ANSWER: dry saturated Explanation: No explanation is available for this question!

34)   The engines which are operating on gas power cycle are

a. cyclic
b. non-cyclic
c. either cyclic or non-cyclic
d. none of the above
 Answer  Explanation  Related Ques ANSWER: either cyclic or non-cyclic Explanation: No explanation is available for this question!

35)   Internal combustion engine is the example of

a. cyclic heat engine
b. non-cyclic heat engine
c. both a. and b.
d. none of the above
 Answer  Explanation  Related Ques ANSWER: non-cyclic heat engine Explanation: No explanation is available for this question!

36)   The cycle which consists of two reversible isotherms and two reversible isochores is called as

a. Rankine cycle
b. Carnot cycle
c. Stirling cycle
d. Ericsson cycle
 Answer  Explanation  Related Ques ANSWER: Stirling cycle Explanation: No explanation is available for this question!

37)   Two reversible isothermal processes and two reversible isobaric processes are carried out in

a. Rankine cycle
b. Carnot cycle
c. Stirling cycle
d. Ericsson cycle
 Answer  Explanation  Related Ques ANSWER: Ericsson cycle Explanation: No explanation is available for this question!

38)   Which thermodynamic cycle, for the same condition, has highest efficiency among the others?

a. Carnot cycle
b. Stirling cycle
c. Ericsson cycle
d. None. All of the above have same efficiency
 Answer  Explanation  Related Ques ANSWER: None. All of the above have same efficiency Explanation: No explanation is available for this question!

39)   What is the correct formula for net work done of reciprocating engine?

a. Wnet = mean effective pressure × clearance volume
b. Wnet = mean effective pressure × total volume of cylinder
c. Wnet = mean effective pressure × displacement volume
d. none of the above
 Answer  Explanation  Related Ques ANSWER: Wnet = mean effective pressure × displacement volume Explanation: No explanation is available for this question!

40)   What is the reason of the fact that the internal combustion engine does not complete thermodynamic cycle?

a. because every time fresh air is taken inside the engine and combustion products are thrown out of the engine
b. because permanent chemical change is undergone by the working fluid in combustion chamber
c. both a. and b.
d. none of the above
 Answer  Explanation  Related Ques ANSWER: both a. and b. Explanation: No explanation is available for this question!

41)   The heat pump

a. receives heat from high temperature region and discharge it to low temperature region with production of useful work
b. receives heat from low temperature region and discharge it to high temperature region with production of useful work
c. receives heat from high temperature region and discharge it to low temperature region with utilization of external work
d. receives heat from low temperature region and discharge it to high temperature region with utilization of external work
 Answer  Explanation  Related Ques ANSWER: receives heat from low temperature region and discharge it to high temperature region with utilization of external work Explanation: No explanation is available for this question!

42)   What is correct formula for calculating COP of heat pump? a. [COP]H. P. = Q1 / W
b. [COP]H. P. = Q2 / W
c. [COP]H. P. = W / Q1
d. [COP]H. P. = W / Q2
 Answer  Explanation  Related Ques ANSWER: [COP]H. P. = Q1 / W Explanation: No explanation is available for this question!

43)   How is the COP of a refrigerator calculated? a. [COP]Ref. = Q1 / W
b. [COP]Ref. = Q2 / W
c. [COP]Ref. = W / Q1
d. [COP]Ref. = W / Q2
 Answer  Explanation  Related Ques ANSWER: [COP]Ref. = Q2 / W Explanation: No explanation is available for this question!

44)   Where is main concentration in refrigeration for its calculation?

a. high temperature reservoir
b. low temperature reservoir
c. both high temperature and low temperature reservoirs
d. none of the above
 Answer  Explanation  Related Ques ANSWER: low temperature reservoir Explanation: No explanation is available for this question!

45)   What is the relation between [COP]H. P. = [COP]Ref.?

a. [COP]H. P. = [COP]Ref.
b. [COP]H. P. + [COP]Ref. = 1
c. [COP]H. P. – [COP]Ref. = 1
d. [COP]H. P. × [COP]Ref. = 1
 Answer  Explanation  Related Ques ANSWER: [COP]H. P. – [COP]Ref. = 1 Explanation: No explanation is available for this question!

46)   What is the effect of decrease in temperature difference between two reservoirs of heat pump on its COP?

a. COP increases with decreases in temperature difference between two reservoirs
b. COP decreases with decreases in temperature difference between two reservoirs
c. COP does not affected by change in temperature difference between two reservoirs
d. cannot say
 Answer  Explanation  Related Ques ANSWER: COP increases with decreases in temperature difference between two reservoirs Explanation: No explanation is available for this question!

47)   Dry air does NOT contain

a. krypton
b. argon
c. neon
d. none of the above
 Answer  Explanation  Related Ques ANSWER: none of the above Explanation: No explanation is available for this question!

48)   The ratio of partial pressure of water vapour in a mixture to the saturation pressure of water at the same temperature of the mixture is called as

a. humidity
b. partial humidity
c. specific humidity
d. relative humidity
 Answer  Explanation  Related Ques ANSWER: relative humidity Explanation: No explanation is available for this question!

49)   What is the specific humidity?

a. the ratio of the mass of water vapour to the mass of the total mixture of air and water vapour
b. the ratio of the mass of dry air to the mass of the total mixture of air and water vapour
c. the ratio of the mass of dry air to the mass of water vapour in a mixture of air and water vapour
d. the ratio of the mass of water vapour to the mass of dry air in a mixture of air and water vapour
 Answer  Explanation  Related Ques ANSWER: the ratio of the mass of water vapour to the mass of dry air in a mixture of air and water vapour Explanation: No explanation is available for this question!

50)   The boiler in which the tubes are surrounded by hot gases is called as

a. fire tube boiler
b. water tube boiler
c. both a. and b.
d. none of the above
 Answer  Explanation  Related Ques ANSWER: water tube boiler Explanation: No explanation is available for this question!