# Thermodynamics Test Questions Set - 2

1)   The properties of a system whose values depend upon mass of the system are called as

a. intensive properties
b. extensive properties
c. dependent properties
d. massive properties
 Answer  Explanation  Related Ques ANSWER: extensive properties Explanation: Extensive properties depend upon mass in the system whereas intensive properties are independent of mass of the system. Volume, energy etc. are some of the examples of extensive properties. They are dependent upon mass of the system.

2)   Which law of thermodynamics is the basis of temperature measurement?

a. Zeroth law of thermodynamics
b. First law of thermodynamics
c. Second law of thermodynamics
d. none of the above
 Answer  Explanation  Related Ques ANSWER: Zeroth law of thermodynamics Explanation: When a body A is in thermal equilibrium with a body B, And also the same body A is in thermal equilibrium with a body C, then body B and body C are also in thermal equilibrium with each other. This is called as Zeroth Law of Thermodynamics. It is the basis of temperature measurement.

3)   Consider a piston cylinder arrangement with gas filled in cylinder. If the piston moves from position 1 to position 2 as shown in figure with volume changes from v1 to v2, the amount of work W by the system will be, a. v1v2 p dV
b. v1v2 p V
c. v1v2 v dp
d. none of the above
 Answer  Explanation  Related Ques ANSWER: v1 ∫ v2 p dV Explanation: Initially at position 1, let the pressure and volume be p1 and V1 respectively. The piston is the only boundary which moves with gas pressure. Let the piston move out to a new final position 2. The pressure and volume will be p2 and V2 respectively. At any intermediate point let the pressure be p and volume be V. These macroscopic properties are significant for equilibrium state. When the piston moves as infinitesimal distance dl, and area of the piston is 'a', the force F acting on the piston F = p*a and the infinitesimal amount of work done by the gas will be,dW = F * dl = padl = pdVwhere dV= adlTherefore, total work done W by the piston when it moves out from position 1 to position 2 will be,W = v1 ∫ v2 p dV

4)   A system changes its state from state 1 to state 2 through path A and returns from state 2 to state 1 through path B. Path C is also an alternate returning path from state 2 to state 1 as shown in figure. What will be the effect on change in internal energy of the system(ΔE), if the system undergoes these different paths A, B and C? a. ΔE of path C will be greater then ΔE of path B and path A
b. ΔE of path A and path C are equal but ΔE of path B is different than rest
c. ΔE of all the paths are equal
d. none of the above
 Answer  Explanation  Related Ques ANSWER: ΔE of all the paths are equal Explanation: According to the description of path given, through the path A and path B system undergoes cycle,Writing the first law equation for path A,QA = ΔEA + WAand for path B,QB = ΔEB + WBThe processes A and B together constitute a cycle, for which(∑ W)cycle = (∑ Q)cycleWA + WB = QA + QB QA – WA = WB – QBΔEA = – ΔEBSimilarly, when the system returns from state 2 to state 1 through path C,ΔEA = – ΔECTherefore,ΔEB = ΔECTherefore above equations show that the change in internal energy between two states of the system is the same, no matter which path may system follow.

5)   The thermal energy reservoir from which heat is transferred to the system which works on heat engine cycle is called as

a. source
b. sink
c. atmosphere
d. all of the above
 Answer  Explanation  Related Ques ANSWER: source Explanation: Explanation :The thermal energy reservoir from which heat is transferred to the system which works on heat engine cycle is called as source and the thermal energy reservoir to which heat is rejected from the system is called as sink as shown in the diagram. 6)   Which among the following is/are example/s of sink?

a. River
b. Sea
c. Atmosphere
d. all of the above
 Answer  Explanation  Related Ques ANSWER: all of the above Explanation: Sink is the thermal energy reservoir to which heat is rejected from the system which works on heat engine cycle. Heat engine utilizes the heat energy coming from the source and produces work output. But all the heat energy from the source is not converted into work and some amount of heat energy is rejected to the thermal energy reservoir which is called as sink. The above examples river, sea and atmosphere are huge enough that if some heat is rejected to them then there will not be any considerable change in their temperatures. Therefore they are the examples of sink.

7)   Which among the following are the examples of mechanical energy reservoir?

(1) Furnace where fuel is continuously burning
(2) Raised weight
(3) Flywheel in running condition
(4) Compressed spring

a. (1), (2) and (4)
b. (1), (2) and (3)
c. (1), (3) and (4)
d. (2), (3) and (4)
 Answer  Explanation  Related Ques ANSWER: (2), (3) and (4) Explanation: A mechanical energy reservoir is a large body which can store work as potential energy. This large body is covered by an adiabatic wall. Among the above examples, furnace can not store work as potential energy. So furnace will not be the example of mechanical energy reservoirs. Raised weight, running flywheel and compressed spring can store the work as the potential energy.

8)   In the heat engine cycle

a. work output is greater than heat input
b. work output is less than heat input
c. work output is equal to heat input
d. none of the above
 Answer  Explanation  Related Ques ANSWER: work output is less than heat input Explanation: Heat engine utilizes the heat energy coming from the source and produces work output. But all the heat energy from the source is not converted into work and some amount of heat energy is rejected to the thermal energy reservoir which is called as sink. Therefore complete conversion of heat energy into work output is not possible. Therefore, work output is less than heat input.

9)   It is impossible to produce a heat engine, whose sole effect is to absorb energy in the form of heat from a heat source and produce an equal amount of work. This statement is

a. Kelvin-Planck statement
b. Clausius statement
c. Third law of thermodynamics
d. none of the above
 Answer  Explanation  Related Ques ANSWER: Kelvin-Planck statement Explanation: In heat engine, net work output is always less than heat input. Hence total heat energy transferred to the heat engine can not be converted completely into work output. Therefore efficiency of a heat engine is always less that 100%. Thus, it is impossible to produce a heat engine, whose sole effect is to absorb energy in the form of heat from a heat source and produce an equal amount of work. This is a Kelvin-Planck statement.

10)   If a heat engine produces net work output by exchanging heat with only one reservoir, then the heat engine will be,

a. perpetual motion machine of first kind (PMM1)
b. perpetual motion machine of second kind (PMM2)
c. perpetual motion machine of third kind (PMM3)
d. none of the above
 Answer  Explanation  Related Ques ANSWER: perpetual motion machine of second kind (PMM2) Explanation: When a heat engine produces net work output by exchanging heat with only one reservoir, then it will be represented as, In the above diagram, the heat engine is utilizing input heat energy and converting it completely into work output. According to the Kelvin-Planck statement of second law of thermodynamics, it is impossible to produce a heat engine, whose sole effect is to absorb energy in the form of heat from a heat source and produce an equal amount of work. This is due to that some heat has to be rejected to sink. Therefore this heat engine violates the Kelvin-Planck statement of second law of thermodynamics. Hence it will be a perpetual motion machine of second kind (PMM2). PMM2 is impossible to produce.

11)   Two reversible paths P1 and P2 are represented in the figure and the process represented is a cyclic process. Which will be the correct relation for the cyclic process shown? a. Cyclic ∫P1 P2 (dQ/T) = 0
b. 12 P1 (dQ/T) = 12 P2 (dQ/T)
c. 12 P1 (dQ/T) = 21 P2 (dQ/T)
d. all of the above
 Answer  Explanation  Related Ques ANSWER: all of the above Explanation: No explanation is available for this question!

12)   Which type of function the entropy is?

a. a path function
b. a point function
c. both a. and b.
d. none of the above
 Answer  Explanation  Related Ques ANSWER: a point function Explanation: No explanation is available for this question!

13)   100 kg of ice at 0 °C is melted completely. What will be the change in entropy in kJ/K, when T2 = 0 °C and latent heat of fusion of ice is taken as 334.774 J/g

a. 0
b. 100.6
c. 122.6
d. 150.6
 Answer  Explanation  Related Ques ANSWER: 122.6 Explanation: No explanation is available for this question!

14)   The entropy is

a. an intensive property
b. an extensive property
c. both a. and b.
d. none of the above
 Answer  Explanation  Related Ques ANSWER: an extensive property Explanation: No explanation is available for this question!

15)   How is the entropy change of any irreversible process estimated, when the process is connecting two equilibrium points A and B?

a. by replacing the original process by reversible zigzag path containing reversible adiabatic followed by isothermal and then again reversible adiabatic process between the same equilibrium points A and B
b. by replacing a reversible path between the same equilibrium points A and B
c. both a. and b.
d. none of the above
 Answer  Explanation  Related Ques ANSWER: by replacing a reversible path between the same equilibrium points A and B Explanation: No explanation is available for this question!

16)   Isentropic (Entropy S=constant) process is also

a. a reversible isothermal process
c. a reversible isobaric process
d. a reversible isochoric process
 Answer  Explanation  Related Ques ANSWER: a reversible adiabatic process Explanation: No explanation is available for this question!

17)   Carnot cycle contains two reversible adiabatic process and

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

18)   What is the relation between the pressure change (dp) and volume change (dv), for all the real processes in nature containing pressure change (dp) as well as volume change (dv)?

a. dp/dv = 0
b. dp/dv > 0
c. dp/dv < 0
d. all the above options are possible
 Answer  Explanation  Related Ques ANSWER: dp/dv < 0 Explanation: No explanation is available for this question!

19)   What is the dead state of the system?

a. the state at which system is in pressure and temperature equilibrium with the surroundings
b. the state at which system is in chemical equilibrium with the surroundings
c. the state at which system must have zero velocity and minimum potential energy
d. all of the above
 Answer  Explanation  Related Ques ANSWER: all of the above Explanation: No explanation is available for this question!

20)   What is the exergy of a system when it is at dead state?

a. zero
b. less than zero
c. more than zero
d. cannot say
 Answer  Explanation  Related Ques ANSWER: zero Explanation: No explanation is available for this question!

21)   Which in the examples is NOT a pure substance?

a. baking soda
b. diamond
c. sea water
d. table salt
 Answer  Explanation  Related Ques ANSWER: sea water Explanation: No explanation is available for this question!

22)   Which is a state of a substance from which a phase change occurs without a change of pressure or temperature?

a. pure state
b. phase state
c. saturation state
d. critical state
 Answer  Explanation  Related Ques ANSWER: saturation state Explanation: No explanation is available for this question!

23)   What is the volume of a gram mole of hydrogen at 760 mm Hg and 0 °C ?

a. 22.4 cm3
b. 22.4 liters
c. 22.4 m3
d. none of the above
 Answer  Explanation  Related Ques ANSWER: 22.4 liters Explanation: No explanation is available for this question!

24)   What is the formula for number of kg moles (n) of a gas? If,
m = mass of gas in kg
μ = molecular weight in kg / kg mole

a. n = m . μ
b. n = m / μ
c. n = μ / m
d. none of the above
 Answer  Explanation  Related Ques ANSWER: n = m / μ Explanation: No explanation is available for this question!

25)   The following graph shows the T-p relation of gas after throttling when pressure and temperature before throttling are kept constant. The curve shown in graph is an isenthalpic curve. What is the value of the slop of the curve called? a. Throttling coefficient
b. Joule-Kelvin coefficient
c. Isenthalpic coefficient
d. none of the above
 Answer  Explanation  Related Ques ANSWER: Joule-Kelvin coefficient Explanation: No explanation is available for this question!

26)   What is the effect on temperature of an ideal gas, when it undergoes a Joule-Kelvin expansion?

a. temperature increases
b. temperature decreases
c. first temperature increases and then decreases isenthalpically
d. no change in temperature
 Answer  Explanation  Related Ques ANSWER: no change in temperature Explanation: No explanation is available for this question!

27)   In the following T-s diagram of Rankine cycle, process (1-2) is heat addition in boiler, process (2-3) is an expansion at turbine, process (3-4) is a condensation process and process (4-1) is a pumping process at feed pump. What is the formula for efficiency of Rankine cycle? a. ηRankine = ((h2 – h3) + (h1 – h4)) / (h2 – h1)
b. ηRankine = ((h2 – h3) – (h1 – h4)) / (h2 – h1)
c. ηRankine = (h2 – h3) / (h2 – h1)
d. none of the above
 Answer  Explanation  Related Ques ANSWER: ηRankine = ((h2 – h3) – (h1 – h4)) / (h2 – h1) Explanation: No explanation is available for this question!

28)   Sometimes the pump work in vapour power cycle is neglected because

a. the pump work in not considered in efficiency of vapour power cycle
b. the pump work is very small compared to the heat addition
c. the pump work is very small compared to the turbine work
d. none of the above
 Answer  Explanation  Related Ques ANSWER: the pump work is very small compared to the heat addition Explanation: No explanation is available for this question!

29)   How is the capacity of vapour power plant expressed?

a. in terms of heat rate
b. in terms of steam rate
c. in terms of work output
d. none of the above
 Answer  Explanation  Related Ques ANSWER: in terms of steam rate Explanation: No explanation is available for this question!

30)   What is heat rate in steam power plant?

a. the rate of heat input in kJ per heat input in kW
b. the rate of heat input in kJ required to produce unit turbine work (1 kW)
c. the rate of heat input in kJ required to produce unit net shaft work (1 kW)
d. none of the above
 Answer  Explanation  Related Ques ANSWER: the rate of heat input in kJ required to produce unit net shaft work (1 kW) Explanation: No explanation is available for this question!

31)   What is the highlighted area (area enclosed by 1234) in the following T-s diagram of vapour power cycle indicate? b. work produced by turbine
c. net work produced by cycle
d. heat rejected from cycle
 Answer  Explanation  Related Ques ANSWER: net work produced by cycle Explanation: No explanation is available for this question!

32)   To maximize the work output at turbine, the specific volume of working fluid should be

a. as small as possible
b. as large as possible
c. constant throughout the cycle
d. none of the above
 Answer  Explanation  Related Ques ANSWER: as large as possible Explanation: No explanation is available for this question!

33)   For the same pressure ratio, what is the relation between work required to compress steam in vapour form and work required to compress steam in liquid form?

a. work required to compress steam in vapour form is equal work required to compress steam in liquid form
b. work required to compress steam in vapour form is more than work required to compress steam in liquid form
c. work required to compress steam in vapour form less than work required to compress steam in liquid form
d. cannot say
 Answer  Explanation  Related Ques ANSWER: work required to compress steam in vapour form is more than work required to compress steam in liquid form Explanation: No explanation is available for this question!

34)   The purpose of study of air standard cycle is

a. to simplify the analysis of internal combustion engine
b. to increase the efficiency of internal combustion engine
c. both a. and b.
d. none of the above
 Answer  Explanation  Related Ques ANSWER: to simplify the analysis of internal combustion engine Explanation: No explanation is available for this question!

35)   Otto cycle is the air standard cycle of

a. spark ignition (SI) engine
b. compression (CI) ignition engine
c. both SI and CI engines
d. none of the above
 Answer  Explanation  Related Ques ANSWER: spark ignition (SI) engine Explanation: No explanation is available for this question!

36)   How is the heat added in the Otto cycle?

a. reversibly at constant pressure
b. irreversibly at constant pressure
c. reversibly at constant volume
d. irreversibly at constant volume
 Answer  Explanation  Related Ques ANSWER: reversibly at constant volume Explanation: No explanation is available for this question!

37)   What is the formula for compression (rk) ratio of the Otto cycle?

a. rk = Volume of cylinder at the beginning of compression / Volume of cylinder at the end of compression
b. rk = Volume of cylinder at the end of compression / Volume of cylinder at the beginning of compression
c. rk = Volume of cylinder at the end of compression / clearance volume
d. none of the above
 Answer  Explanation  Related Ques ANSWER: rk = Volume of cylinder at the beginning of compression / Volume of cylinder at the end of compression Explanation: No explanation is available for this question!

38)   What is the relation between compression ratio (rk) and the efficiency of the Otto cycle?

a. efficiency decreases with increase in compression ratio
b. efficiency increases with increase in compression ratio
c. efficiency does not affected by change in compression ratio
d. none of the above
 Answer  Explanation  Related Ques ANSWER: efficiency increases with increase in compression ratio Explanation: No explanation is available for this question!

39)   The compression ratio cannot be increased beyond certain limit, because it results to

a. auto-ignition of fuel
b. detonation
c. engine knocking
d. all of the above
 Answer  Explanation  Related Ques ANSWER: all of the above Explanation: No explanation is available for this question!

40)   Use of gasoline blend like gasoline mixed with tetraethyl lead in internal combustion engine

a. increases the octane rating of the fuel
b. allows engine to operate at higher compression ratio
c. avoids auto-ignition of fuel
d. all of the above
 Answer  Explanation  Related Ques ANSWER: all of the above Explanation: No explanation is available for this question!

41)   The ideal refrigeration cycle is like

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

42)   Which device is used for the expansion of refrigerant in vapour compression refrigeration cycle?

a. throttling valve
b. capillary tube
c. either throttling valve or capillary tube
d. none of the above
 Answer  Explanation  Related Ques ANSWER: either throttling valve or capillary tube Explanation: No explanation is available for this question!

43)   Wet compression is ______.

a. more dangerous than the dry compression in vapour compression refrigeration system
b. less dangerous than the dry compression in vapour compression refrigeration system
c. equally preferable in vapour compression refrigeration system
d. cannot say
 Answer  Explanation  Related Ques ANSWER: more dangerous than the dry compression in vapour compression refrigeration system Explanation: No explanation is available for this question!

44)   How is the condensation process in vapour compression refrigeration cycle carried out?

a. at constant volume
b. at constant pressure
c. at constant enthalpy
d. all of the above
 Answer  Explanation  Related Ques ANSWER: at constant pressure Explanation: No explanation is available for this question!

45)   What is flash gas fraction?

a. the mass fraction of liquid in liquid-vapour mixture of refrigerant at inlet to the evaporator

b. the mass fraction of vapour in liquid-vapour mixture of refrigerant at inlet to the evaporator

c. the mass of vapour actually compressed to the mass of vapour should have compressed ideally

d. none of the above
 Answer  Explanation  Related Ques ANSWER: the mass fraction of vapour in liquid-vapour mixture of refrigerant at inlet to the evaporator Explanation: No explanation is available for this question!

46)   In evaporation process of vapour compression refrigeration system

a. heat is rejected from refrigerant to surroundings
b. heat is rejected from surroundings to refrigerant
c. only pressure change takes place
d. none of the above
 Answer  Explanation  Related Ques ANSWER: heat is rejected from surroundings to refrigerant Explanation: No explanation is available for this question!

47)   What is the relative humidity for a saturated air?

a. 0%
b. 50%
c. 100%
d. cannot say
 Answer  Explanation  Related Ques ANSWER: 100% Explanation: No explanation is available for this question!

48)   What is the degree of saturation?

a. the ratio of the actual relative humidity to the saturated specific humidity at the same temperature
b. the ratio of the actual specific humidity to the saturated specific humidity at the same temperature
c. the ratio of the saturated specific humidity to the actual specific humidity at the same temperature
d. none of the above
 Answer  Explanation  Related Ques ANSWER: the ratio of the actual specific humidity to the saturated specific humidity at the same temperature Explanation: No explanation is available for this question!

49)   The degree of saturation varies between

a. 1 to infinity
b. 0 to infinity
c. 0 to 1
d. none of the above
 Answer  Explanation  Related Ques ANSWER: 0 to 1 Explanation: No explanation is available for this question!

50)   Comparing fire tube and water tube boilers, which boiler can produce comparatively higher pressure steam than another for the same capacity?

a. fire tube boiler
b. water tube boiler
c. both can produce steam at same pressure for the same capacity
d. none of the above
 Answer  Explanation  Related Ques ANSWER: water tube boiler Explanation: No explanation is available for this question!