# Thermodynamics Test Questions - Set - 3

1)   Which among the following is an intensive property of a system?

a. Volume
b. Energy
c. Pressure
d. all of the above
 Answer  Explanation  Related Ques ANSWER: Pressure Explanation: Intensive properties are independent of mass in a system and pressure does not depend upon mass in the system. Pressure, temperature etc. are some of the examples of intensive properties.

2)   The characteristic of a material or a body which is taken as an indication of change in temperature is known as

a. Thermodynamics property
b. Thermostatic property
c. Thermometric property
d. none of the above
 Answer  Explanation  Related Ques ANSWER: Thermometric property Explanation: Thermal equilibrium is achieved by heat transfer between two bodies which are at different temperature. To obtain a quantitative measure of the temperature of any body, a reference body is used and a particular physical characteristic of that reference body is selected which changes with temperature. The change in the selected characteristic is the indication as change in temperature. This selected characteristic is called as thermometric property, and the reference body is called as thermometer. Mercury is a common example of the thermometer.

3)   Work involved in a thermodynamic process is

a. a path function
b. a point function
c. a transfer function
d. none of the above
 Answer  Explanation  Related Ques ANSWER: a path function Explanation: As shown in above diagram, the thermodynamic system can be taken from state 1 to state 2 along many quasi-static paths like path A, B or C. The area under the curve indicates the amount of work done for each process. But those areas under each curve is different. Therefore the work involved does not depend upon the final state B but it depends upon the path by which the system is taken to the final state. Thus the work involved in thermodynamic process is a path function.

4)   Consider the below diagram of heat transfer and work transfer for a system. What will be the first law equation for the below system? a. (Q1 – Q2) = ΔE – ( W2 + W3 – W1 )
b. (Q1 + Q2) = ΔE + ( W2 – W3 + W1 )
c. (Q1 – Q2) = ΔE + ( W2 + W3 – W1 )
d. none of the above
 Answer  Explanation  Related Ques ANSWER: (Q1 – Q2) = ΔE + ( W2 + W3 – W1 ) 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(ΔE).Q – W = ΔETherefore, Q = ΔE + W

5)   Clausius statement is related to

a. heat engine operating in a cycle
b. heat pump operating in a cycle
c. both a. and b.
d. none of the above
 Answer  Explanation  Related Ques ANSWER: heat pump operating in a cycle Explanation: Clausius statement of second law of thermodynamics states that, it is impossible to construct a device (heat pump), operating in a cycle, whose sole effect is to transfer of heat from a cooler body to a hotter body, without expending any work input. Heat pump is a device which transfers heat from a cooler body to a hotter body but with expending considerable amount of work. Heat always flows from a hotter body to cooler body spontaneously, but the reverse of this is not possible spontaneously. Heat cannot flow of itself from body at a lower temperature to a body at a higher temperature. Some work has to be expended to run a heat pump.

6)   Considering following schematic diagram of refrigerator, the coefficient of performance (COP)ref of refrigerator is given by, a. [COP]ref = Q1/Q2
b. [COP]ref = Q2/Q1
c. [COP]ref = Q1/W
d. [COP]ref = Q2/W
 Answer  Explanation  Related Ques ANSWER: [COP]ref = Q2/W Explanation: Refrigerator is a device, which operates in a cycle and maintains the temperature a particular body lower than the surrounding temperature. In the above diagram of a refrigerator the body A is maintained at a temperature (t1) lower that the temperature of surrounding (t2). So the desired effect is concentrated at the body A that is Q2, not at the surrounding. The COP is calculated by the formula,COP = Desired effect / Work inputCOP = Q2 / WHence the answer is d.

7)   Which among the following is correct relation between COP of heat pump and COP of refrigerator?

a. [COP]H.P. = 1 + [COP]ref
b. [COP]H.P. = 1 – [COP]ref
c. [COP]H.P. = [COP]ref
d. none of the above
 Answer  Explanation  Related Ques ANSWER: [COP]H.P. = 1 + [COP]ref Explanation: The COP of a device, operating in a cycle is given by,[COP] = Desired effect / Work inputIn refrigerator, the desired effect is to maintain temperature of the body A lower than the surrounding temperature.Therefore, A refrigerator is a device, which operates in a cycle and maintains the temperature a particular body lower than the surrounding temperature.[COP]ref = Desired effect / Work input[COP]ref = Q2 / W[COP]H.PAnd in heat pump, the desired effect is to maintain temperature of the body B more than the surrounding temperature.Therefore, [COP]H.P. = Desired effect / Work input[COP]H.P = Q1 / Wand the work input is given by, W = Q1 – Q2 From the equations of [COP]ref and [COP]H.P ,[COP]H.P. = 1 + [COP]ref

8)   COP of a heat pump is

a. always less than infinity (COP < ∞ )
b. always less that 1 (COP < 1)
c. always equals to 1 (COP = 1)
d. always equals to infinity (COP = ∞ )
 Answer  Explanation  Related Ques ANSWER: always less than infinity (COP < ∞ ) Explanation: Heat pump is a device, which operates in a cycle and maintains the temperature a particular body higher than the surrounding temperature. The desired effect is to maintain the temperature of a body higher than the surrounding temperature. Therefore COP of the heat pump is given by the equation,[COP]H.P. = Desired effect / Work input[COP]H.P = Q1 / W According to the Clausius statement of second law of thermodynamics, it is impossible to construct a heat pump, operating in a cycle, whose sole effect is to transfer of heat from a cooler body to a hotter body, without expending any work input.Therefore, work input W will never be zero. Thus COP of heat pump is always less than infinity (COP < ∞)

9)   Considering relation between Kelvin-Planck and Clausius statement, if one statement between the two is violated then

a. other one may be or may not be violated
b. other one is also violated
c. other one must be correct
d. none of the above
 Answer  Explanation  Related Ques ANSWER: other one is also violated Explanation: Kelvin-Planck and Clausius statements look different but both are are the parallel statements of second law of thermodynamics. Consider, a heat pump absorbs heat Q1 from a cold reservoir which is at temperature T2 and transfers it to a hot reservoir which is at temperature T1 without expenditure of any work. This heat pump violates the Clausius statement.Now consider, a heat engine absorbs same heat Q1 which is transferred by heat pump in the hot reservoir at temperature T1 and produces a new work W and rejects some heat energy Q2 to the cold reservoir at temperature T2, as heat engine absorbs heat Q1 which is the same heat absorbed by heat pump from the cold reservoir at T2. It shows that the heat engine is exchanging heat only with single reservoir at single fixed temperature T2. This violates the Kelvin-Planck statement.Therefore, if one statement between the Kelvin-Planck and Clausius statement is violated, then the other one is also violated.

10)   In which process, every state passes by the system is an equilibrium state?

a. quasi-static process
b. reversible process
c. both a. and b.
d. none of the above
 Answer  Explanation  Related Ques ANSWER: both a. and b. Explanation: A reversible process is the process in which, after completing the process, both the system and surroundings can be restored to their initial state, without producing any change is the rest of the universe. equivalence of kelvin planck and clausius statement. Let us consider a system is at state 1 and it is taken to the state 1 quasi-statically by following a path 1-2. Again the system is taken reversibly to its initial state 1 from state 2 again quasi-statically by following the same path 2-1. Then this process is called reversible process. A reversible process is carried out infinitely slowly, so that every state passed through by the system is an equilibrium state. Thus reversible process coincides with a quasi-static process.

11)   The diagram below shows the Carnot cycle. What is the total quantity of heat added in the system? a. (area under 4-1)
b. (area under 4-1) – (area under 2-3)
c. (area enclosed by 1-2-3-4)
d. none of the above
 Answer  Explanation  Related Ques ANSWER: (area under 4-1) Explanation: No explanation is available for this question!

12)   What is the criterion provided by Clausius inequality for the process which is impossible?

a. Cyclic ∫ (đQ/T) = 0
b. Cyclic ∫ (đQ/T) > 0
c. Cyclic ∫ (đQ/T) < 0
d. all above processes are possible
 Answer  Explanation  Related Ques ANSWER: Cyclic ∫ (đQ/T) > 0 Explanation: No explanation is available for this question!

13)   How are the efficiencies of any heat engine (η) and reversible heat engine (ηR) compared, when both are operating between same heat source and same heat sink?

a. η = ηR
b. η > ηR
c. η < ηR
d. cannot say
 Answer  Explanation  Related Ques ANSWER: η < ηR Explanation: No explanation is available for this question!

14)   What is the relation between heat rejected by any heat engine (Q2) and heat rejected by reversible heat engine (Q2R), when both are operating between same heat source and same heat sink?

a. Q2 = Q2R
b. Q2 < Q2R
c. Q2 > Q2R
d. cannot say
 Answer  Explanation  Related Ques ANSWER: Q2 > Q2R Explanation: No explanation is available for this question!

15)   What is the entropy change (dSiso) of a reversible isolated (dQ=0) process?

a. dSiso = 0
b. dSiso > 0
c. dSiso < 0
d. none of the above
 Answer  Explanation  Related Ques ANSWER: dSiso = 0 Explanation: No explanation is available for this question!

16)   What is the entropy change (dSiso) of an irreversible isolated (dQ=0) process?

a. dSiso = 0
b. dSiso > 0
c. dSiso < 0
d. none of the above
 Answer  Explanation  Related Ques ANSWER: dSiso > 0 Explanation: No explanation is available for this question!

17)   Which condition is correct according to the entropy principle?

a. the entropy of an isolated system can never decreases
b. the entropy of a system remains constant only when the process is reversible
c. the entropy of a system increases when the process is irreversible
d. all of the above
 Answer  Explanation  Related Ques ANSWER: all of the above Explanation: No explanation is available for this question!

18)   What is available energy (A. E.)

a. Energy supplied to a cyclic heat engine
b. Maximum energy utilized to produce maximum work from a certain heat supplied to a cyclic heat engine
c. Minimum heat energy rejected to sink by second law
d. Maximum heat energy rejected to sink by second law
 Answer  Explanation  Related Ques ANSWER: Maximum energy utilized to produce maximum work from a certain heat supplied to a cyclic heat engine Explanation: No explanation is available for this question!

19)   What is unavailable energy (U. E.)

a. Energy supplied to a cyclic heat engine
b. Maximum energy utilized to produce maximum work from a certain heat supplied to a cyclic heat engine
c. Minimum heat energy rejected to sink by second law
d. Maximum heat energy rejected to sink by second law
 Answer  Explanation  Related Ques ANSWER: Minimum heat energy rejected to sink by second law Explanation: No explanation is available for this question!

20)   What is the effect on exergy output of a process, when heat is transferred through a finite temperature difference?

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

21)   What is the saturated solid state?

a. a state at which solid can change into liquid at constant pressure but changing temperature
b. a state at which solid can change into liquid at constant temperature but change in pressure
c. a state at which solid can change into liquid at constant pressure and temperature
d. none of the above
 Answer  Explanation  Related Ques ANSWER: a state at which solid can change into liquid at constant pressure and temperature Explanation: No explanation is available for this question!

22)   What is the state, at which saturated liquid line with respect to vaporisation and saturated vapour line on p-v diagram of pure substance, meet called?

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

23)   The volume occupied by one number of unit mol of gas is called as

a. molecular volume
b. mol volume
c. molar volume
d. none of the above
 Answer  Explanation  Related Ques ANSWER: molar volume Explanation: No explanation is available for this question!

24)   A gas being the best behaved thermodynamics substance, what is the relation between the ratio of pressure (p) of a gas at any temperature to pressure (pt) of same gas at triple point temperature and the nature of gas?

a. the ratio (p/pt) approaches a constant value which is dependent of nature of gas
b. the ratio (p/pt) approaches a constant value which is independent of nature of gas
c. the ratio (p/pt) approaches a various values which are dependent of nature of gas
d. none of the above
 Answer  Explanation  Related Ques ANSWER: the ratio (p/pt) approaches a constant value which is independent of nature of gas Explanation: No explanation is available for this question!

25)   What is the inversion curve in isenthalpic expansion or Joule-Kelvin expansion?

a. the locus of all points at which Joule-Kelvin coefficient is negative
b. the locus of all points at which Joule-Kelvin coefficient is positive
c. the locus of all points at which Joule-Kelvin coefficient is zero
d. none of the above
 Answer  Explanation  Related Ques ANSWER: the locus of all points at which Joule-Kelvin coefficient is zero Explanation: No explanation is available for this question!

26)   The temperature at which the inversion curve in the graph of isentropic state of a gas intersects with temperature axis is a. a minimum inversion temperature
b. a maximum inversion temperature
c. a cooling temperature
d. a heating temperature
 Answer  Explanation  Related Ques ANSWER: a maximum inversion temperature Explanation: No explanation is available for this question!

27)   Which is the affecting factor for the fact that turbine work output is more than pump work input in vapour power cycle for the same pressure ratio?

a. specific heat added to the working fluid
b. specific volume of working fluid
c. both a. and b.
d. none of the above
 Answer  Explanation  Related Ques ANSWER: specific volume of working fluid Explanation: No explanation is available for this question!

28)   What is the relation between efficiency of Rankine cycle (ηRankine) and efficiency of actual vapour power cycle (ηActual Cycle)?

a.Rankine) = (ηActual Cycle)
b.Rankine) > (ηActual Cycle)
c.Rankine) < (ηActual Cycle)
d. none of the above
 Answer  Explanation  Related Ques ANSWER: (ηRankine) > (ηActual Cycle) Explanation: No explanation is available for this question!

29)   Which loss does present in actual vapour power cycle at the exit of the boiler and at the entry of the turbine?

a. friction loss
b. constant pressure heat loss
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!

30)   Considering only heat loss (Qloss) in the expansion process at the turbine, what is the correct relation among enthalpies of steam entering and leaving the turbine (h1 and h2 respectively), turbine work (WT) and heat loss (Qloss)

a. h1 = h2 – WT – Qloss
b. h1 = h2 + WT – Qloss
c. h1 = h2 + WT + Qloss
d. none of the above
 Answer  Explanation  Related Ques ANSWER: h1 = h2 + WT + Qloss Explanation: No explanation is available for this question!

31)   How can we differentiate Rankine cycle from Carnot cycle?

a. Heat addition process of Rankine cycle is reversible isothermal whereas heat addition process of Carnot cycle is reversible isobaric
b. Heat addition process of Rankine cycle is reversible isobaric whereas heat addition process of Carnot cycle is reversible isothermal
c. Heat addition process of Rankine cycle is reversible isentropic whereas heat addition process of Carnot cycle is reversible isothermal
d. both cycles are identical except the working fluid used
 Answer  Explanation  Related Ques ANSWER: Heat addition process of Rankine cycle is reversible isobaric whereas heat addition process of Carnot cycle is reversible isothermal Explanation: No explanation is available for this question!

32)   What is the relation between efficiencies of Rankine cycle and Carnot cycle for the same pressure ratio?

a.Rankine) = (ηCarnot)
b.Rankine) > (ηCarnot )
c.Rankine) < (ηCarnot )
d. none of the above
 Answer  Explanation  Related Ques ANSWER: (ηRankine) < (ηCarnot ) Explanation: No explanation is available for this question!

33)   If Tm be the mean temperature of heat addition in Rankine cycle as shown in diagram,
what will the formula for efficiency of Rankine cycle? a.Rankine) = ( T3 / Tm)
b.Rankine) = 1 – (T3 / Tm)
c.Rankine) = 1 – (T2 / Tm)
d.Rankine) = (T2 / Tm)
 Answer  Explanation  Related Ques ANSWER: (ηRankine) = 1 – (T3 / Tm) Explanation: No explanation is available for this question!

34)   How is the efficiency of the SI engine affected by change in specific heat ratio (γ) of the working fluid?

a. the efficiency of the engine increases with increase in specific heat ratio (γ) of the working fluid
b. the efficiency of the engine decreases with increase in specific heat ratio (γ) of the working fluid
c. the efficiency of the engine does not affected by change in specific heat ratio (γ) of the working fluid
d. none of the above
 Answer  Explanation  Related Ques ANSWER: the efficiency of the engine increases with increase in specific heat ratio (γ) of the working fluid Explanation: No explanation is available for this question!

35)   For the same capacity engines, the compression ratio of diesel engine

a. is lower than the compression ratio of SI engine
b. is higher than the compression ratio of SI engine
c. is same as the compression ratio of SI engine
d. cannot say
 Answer  Explanation  Related Ques ANSWER: is higher than the compression ratio of SI engine Explanation: No explanation is available for this question!

36)   Rate of burning in the compression ignition engine can be controlled by

a. rate of injection of fuel
b. rate of air taken into carburetor
c. both a. and b.
d. none of the above
 Answer  Explanation  Related Ques ANSWER: rate of injection of fuel Explanation: No explanation is available for this question!

37)   How is the heat added in the Diesel 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 pressure Explanation: No explanation is available for this question!

38)   The below diagram is the p-v diagram of the Otto, Diesel and Dual cycles for the same compression ratio. Which in the diagram is the path followed by the Diesel cycle? a. 1-2-4-7-1
b. 1-2-3-5-7-1
c. 1-2-6-7-1
d. none of the above
 Answer  Explanation  Related Ques ANSWER: 1-2-6-7-1 Explanation: No explanation is available for this question!

39)   For the same maximum pressure and temperature, what is the relation among the efficiencies of the Otto cycle, the Diesel cycle and the Dual cycle?

a. ηDual > ηDiesel > ηOtto
b. ηDiesel > ηDual > ηOtto
c. ηDiesel > ηOtto > ηDual
d. ηOtto > ηDiesel > ηDual
 Answer  Explanation  Related Ques ANSWER: ηDiesel > ηDual > ηOtto Explanation: No explanation is available for this question!

40)   The Brayton cycle which is used in aircraft, automotive is

a. a closed cycle
b. an open cycle
c. either closed or open cycle
d. cannot say
 Answer  Explanation  Related Ques ANSWER: an open cycle Explanation: No explanation is available for this question!

41)   The heat required to melt 1 tonne of ice in 12 hours is equivalent to

a. one tonne of refrigeration
b. two tonne of refrigeration
c. half tonne of refrigeration
d. four tonne of refrigeration
 Answer  Explanation  Related Ques ANSWER: two tonne of refrigeration Explanation: No explanation is available for this question!

42)   One tonne of refrigeration is approximately equal to

a. 3.5 kJ / min
b. 3.5 W
c. 211 kW
d. 211 kJ / min
 Answer  Explanation  Related Ques ANSWER: 211 kJ / min Explanation: No explanation is available for this question!

43)   What is the main reason behind subcooling of liquid refrigerant at the condenser outlet in vapour compression refrigeration system?

a. to increase the refrigerating effect
b. to reduce the mass of vapour formed during expansion process
c. to reduce vapour bubbles which obstruct the flow of liquid refrigerant
d. all of the above
 Answer  Explanation  Related Ques ANSWER: all of the above Explanation: No explanation is available for this question!

44)   What is the result of superheating of vapour at the evaporator outlet?

a. no liquid droplets will travel to the compressor
b. the compressor discharge temperature increases
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!

45)   Which expansion device is capable of regulating the flow of refrigerant according to the load on the evaporator?

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

46)   Which compressor is used, when volume flow rate of refrigerant is very large?

a. rotary compressor
b. reciprocating compressor
c. centrifugal compressor
d. none of the above
 Answer  Explanation  Related Ques ANSWER: centrifugal compressor Explanation: No explanation is available for this question!

47)   What is the temperature at which the water vapour in the mixture of water vapour in air, starts condensing called?

a. condensation temperature
b. dew point temperature
c. vaporization temperature
d. all of the above
 Answer  Explanation  Related Ques ANSWER: dew point temperature Explanation: No explanation is available for this question!

48)   The temperature of air recorded by thermometer when the bulb is covered by a cotton wick saturated by water is called as

a. dry bulb temperature
b. wet bulb temperature
c. stream temperature
d. psychrometric temperature
 Answer  Explanation  Related Ques ANSWER: wet bulb temperature Explanation: No explanation is available for this question!

49)   Which temperature can be measured by an instrument called psychrometer?

a. dry bulb temperature
b. wet bulb temperature
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!

50)   What is the purpose of using economizer in the boiler?

a. to heat feedwater by utilizing heat from exhaust gases
b. to heat feedwater by utilizing some heat from superheated steam
c. to superheat steam
d. none of the above
 Answer  Explanation  Related Ques ANSWER: to heat feedwater by utilizing heat from exhaust gases Explanation: No explanation is available for this question!