439 Thermodynamic MCQ For All Mechanical Exams

26)Equation of continuity comes from

  1. a) conservation of energy
  2. b) conservation of mass
  3. c) conservation of work
  4. d) conservation of heat

Ans-B

27)Which of the following represents the steady flow energy equation?

  1. a) Q+Wx=(h2-h1)-(V2-V1)(V2+V1)/2+g(Z2-Z1)
  2. b) Q+Wx=(h2-h1)+(V2-V1)(V2+V1)/2+g(Z2-Z1)
  3. c) Q-Wx=(h2-h1)-(V2-V1)(V2+V1)/2+g(Z2-Z1)
  4. d) Q-Wx=(h2-h1)+(V2-V1)(V2+V1)/2+g(Z2-Z1)

Ans-D

28)When more than one fluid stream is in a control volume, which of the following is more convenient?

  1. a) energy flow per unit time
  2. b) energy flow per unit mass
  3. c) all of the mentioned
  4. d) none of the mentioned

Ans-A

29)In the differential form, the SFEE becomes

  1. a) dQ+dW=dh+VdV+gdZ
  2. b) dQ-dW=dh+VdV+gdZ
  3. c) dQ+dW=dh-VdV-gdZ
  4. d) dQ-dW=dh-VdV+gdZ

Ans-B

30)What does a diffuser do?

  1. a) increases the pressure of the fluid at the expense of its KE
  2. b) decreases the pressure of the fluid and also increases its KE
  3. c) increases the pressure of the fluid and also its KE
  4. d) decreases the pressure of the fluid and also its KE

Ans-A

31)For an insulated nozzle, SFEE of the control surface gives ( considering change in PE is zero and inlet velocity is small compared to exit velocity)

  1. a) V2=sqrt(4*Δh)
  2. b) V2=sqrt(Δh)
  3. c) V2=sqrt(Δh/2)
  4. d) V2=sqrt(2*Δh)

Ans-D

31)Turbines and engines ____ positive power output, and compressors and pumps ____ power input.

  1. a) require, give
  2. b) give, require
  3. c) give, give
  4. d) require, require

Ans-B

32)For an adiabatic compressor or pump,

  1. a) the enthalpy of fluid remains constant with the amount of work input
  2. b) the enthalpy of fluid decreases by the amount of work input
  3. c) the enthalpy of fluid increases by the amount of work input
  4. d) none of the mentioned

Ans-C

33)For an inviscid frictionless fluid flowing through a pipe, Euler equation is given by

  1. a) Vdp+VdV+gdZ=0
  2. b) Vdp-VdV+gdZ=0
  3. c) Vdp-VdV-gdZ=0
  4. d) none of the mentio

Ans-A

34)The Bernoulli equation is restricted to _____ fluids but the SFEE is valid for _____ fluids as well.

  1. a) viscous compressible, frictionless incompressible
  2. b) frictionless incompressible, viscous compressible
  3. c) viscous incompressible, frictionless compressible
  4. d) none of the mentioned

Ans-B

35)Variable flow processes include

  1. a) filling up a gas cylinder
  2. b) evacuating a gas cylinder
  3. c) all of the mentioned
  4. d) none of the mentioned

Ans-C

36)Rate of energy increase within the control volume is given by

  1. a) rate of energy inflow + rate of energy outflow
  2. b) rate of energy inflow – rate of energy outflow
  3. c) rate of energy inflow = rate of energy outflow
  4. d) none of the mentioned

Ans-B

37)Which of the following is true for steady flow?

a)(dE/dt)=0

b)(dE/dt)>0

c)(dE/dt)<0

  1. d) none of the mentioned

Ans-A

38)Variable flow processes can be analysed by

  1. a) system technique
  2. b) constant volume technique
  3. c) both of the mentioned
  4. d) none of the mentioned

Ans-C

39)Using system technique, energy balance for the process comes out to be

  1. a) m2u2+m1u1+(m2-m1)(((V^2)/2)+(h/2))
  2. b) m2u2-m1u1+(m2-m1)(((V^2)/2)+(h/2))
  3. c) m2u2+m1u1-(m2-m1)(((V^2)/2)+(h/2))
  4. d) m2u2-m1u1-(m2-m1)(((V^2)/2)+(h/2))

Ans-D

40)In ____ filling a bottle with air at 300K, the gas temperature rises to 420K due to flow work being converted to ____ increase.

  1. a) adiabatically, heat
  2. b) adiabatically, internal energy
  3. c) constant pressure, heat
  4. d) none of the mentioned

Ans-B

41)For charging a tank,

  1. a) enthalpy is converted to work done
  2. b) work done is converted to enthalpy
  3. c) enthalpy is converted to internal energy
  4. d) internal energy is converted to work done

Ans-C

42)The first law of thermodynamics doesn’t tell us whether a thermodynamic process is feasible or not.

  1. a) true
  2. b) false

Ans-A

43)According to Joule’s experiments,

  1. a) heat can be completely converted into work
  2. b) work can be completely converted into heat
  3. c) both heat and work are completely interchangeable
  4. d) all of the mentioned

Ans-B

44)In a cyclic heat engine there is

  1. a) net heat transfer to the system and net work transfer from the system
  2. b) net heat transfer from the system and net work transfer to the system
  3. c) depends on the conditions of cycle
  4. d) none of the mentioned

Ans-A

45)The function of a heat engine cycle is to _____ continuously at the expense of _____ to the system.

  1. a) heat input, produce work
  2. b) produce work, heat input
  3. c) can be both of the mentioned
  4. d) none of the mentioned

Ans-B

46)A thermal energy reservoir is a large body of

  1. a) small heat capacity
  2. b) large heat capacity
  3. c) infinite heat capacity
  4. d) none of the mentioned

Ans-C

47)If heat rejected from the system Q2 is zero, then

  1. a) net work=Q1 and efficiency=1.00
  2. b) heat is exchanged only with one reservoir
  3. c) it violates the Kelvin-Planck statement
  4. d) all of the mentioned

Ans-D

48)A heat engine has to exchange heat with ___ energy reservoir at ___ different temperatures to produce net work in a complete cycle.

  1. a) one, one
  2. b) one, two
  3. c) two, two
  4. d) none of the mentioned

Ans-C

49)The continual operation of a machine that creates its own energy and thus violates the first law is called

  1. a) PMM2
  2. b) PMM1
  3. c) PMM0
  4. d) none of the mentioned

Ans-B

50)If the second law were not true

  1. a) a ship could be driven by extracting heat from the ocean
  2. b) run a power plant by extracting heat from the air
  3. c) both of the mentioned
  4. d) none of the mentioned

Ans-C

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