DIMENSIONLESS NUMBERS MULTIPLE CHOICE QUESTIONS (MCQ) WITH ANSWERS

DIMENSIONLESS NUMBERS

MULTIPLE CHOICE QUESTIONS

(MCQ) WITH ANSWERS

Dimensionless numbers permit to use

knowledge from experiments. Utilize

 data with one system to another system

with different dimensions. Dimensionless

numbers help to get rid of dimensions. It

extends our knowledge to various other

systems. These increase the level of

understanding and clarity of thought.

These make difficult studies simpler in

heat transfer, mass transfer, momentum

transfer  and fluid mechanics

1. Biot number is applicable to

1. Conduction

2. Convection

3. Radiation

4. None

ANS: (a)

2. Biot number is applicable to

1. Steady state conduction

2. Unsteady state conduction

3. Steady & unsteady state conduction

4. None

ANS: (b)

3. Biot number is applicable to

1. Heat exchangers

2. Radiators

3. Fins

4. None

ANS: (c )

4. Biot number is the ratio of

1. Firstly          Conductive resistance/Convective resistance

2. Secondly     Convective resistance / Conductive resistance

3. Thirdly        Convective resistance /Radiative resistance

4. None

ANS: (a)

5. Different ranges of Biot number

1. One

2. Two

3. Three

4. None

ANS: (c )

6. When Biot number is >0 & < 0.1, which method of analysis is used

1. Lumped parameter method

2. Heisler charts method

3. Gauss Error function method

4. None

ANS: (a)

7. When Biot number is >0.1 & < 100, which method of analysis is used?

1. Lumped parameter method

2. Heisler charts method

3. Gauss Error function method

4. None

ANS: (b)

8. When Biot number is >100 & , which method of analysis is used?

1. Lumped parameter method

2. Heisler charts

3. Gauss Error function method

4. None

ANS: (c)

9. Equation for Biot number is

1. hk/L

2. kL/h

3. hL/k

4. None

ANS: (c )

10. Fourier number is degree of penetration of

1.  Heating in a solid

2. Cooling in a solid

3.  Heating or cooling in a solid

4. None

ANS: (c )

11. Formula for Fourier number is

1. Firstly     ατ/L

2. Secondly      ατ/L²

3. Thirdly          ατ/L³

4. None

ANS: (b)

12. Fourier number is applicable to

1. Conduction

2. Convection

3. Radiation

4. None

ANS: (a)

13. Fourier number is applicable to

1. Steady state conduction

2. Unsteady state conduction

3. Steady & unsteady state conduction

4. None

ANS: (b)

14. Fourier number is applicable to

1. Heat exchangers

2. Radiators

3. Fins

4. None

ANS: (c )

15. Reynolds number is the ratio of

1. Inertia force/Pressure force

2. Pressure force/Inertia force

3. Inertia force/viscous force

4. None

ANS: (c )

16. Reynolds number classify

1. Firstly            Laminar & turbulent flows

2. Secondly       Laminar & transition flows

3. Thirdly           Laminar, transition & turbulent flows

4. None

ANS: (c )

17. The equation for Reynolds number is

1. ρv/D µ

2. Dρµ/v

3. ρvD/µ

4. None

ANS: ( c)

18. Reynolds number for laminar flow in a pipe is

1. Firstly          < 1100

2. Secondly      < 2100

3. Thirdly          > 4000

4. None

ANS: (b)

19. Reynolds number for transition flow in a pipe is

1. Firstly          < 1100 >2100

2. Secondly      <2100 >3100

3. Thirdly          > 2100 <4000

4. None

ANS: (c )

20. Reynolds number for turbulent flow in a pipe is

1. < 2100

2. <400

3. > 400

4. None

ANS: (c )

21. Reynolds number for transition flow over a flat plate is

1. Firstly          > 2 Lacs <4 Lacs

2. Secondly     > 4 Lacs <6 Lacs

3. Thirdly         > 5 Lacs < 7 Lacs

4. None

ANS: (c )

22. Reynolds number for laminar flow over a flat plate is

1. Firstly    ≤ 4 Lacs

2. Secondly    ≤ 5 Lacs

3. Thirdly        ≤ 6 lacs

4. None

ANS: (b)

23. Reynolds number for turbulent flow over a flat plate is

1. Firstly        ≥ 5 Lacs

2. Secondly    ≥ 7 Lacs

3. Thirdly         ≥ 3 lacs

4. None

ANS: (b)

24. The ratio of inertia force to viscous force is

• Fourier number

• Nusselt number

• Reynolds number

• None

ANS: (c )

25. Prandtl number is the ratio of

1. Firstly          Momentum diffusivity/ Thermal diffusivity

2. Secondly     Momentum diffusivity/mass diffusivity

3. Thirdly         Thermal diffusivity/Momentum diffusivity

4. None

ANS: (a)

26. The equation of Prandtl number is

1. µρ/k

2. k/ρc_P

3. µc_p/k

4. None

ANS: (c )

27. Use of Prandtl number is in

1. Free convection

2. Forced convection

3. Free & forced convection

4. None

ANS: (c )

28. Value of Prandtl number for liquid metals is

1. 1 to 100

2. 0.1 to 1

3. 0.01 to 0.003

4. None

ANS: (c )

29. Value of Prandtl number for highly viscous oils is

1. 0-100

2. 100-1000

3. 100-10000

4. None

ANS: (c )

30. Value of Prandtl number for water & air at room temperature is

1. 2 & 0.2

2. 5 & 0.5

3. 7 & 0.7

4. None

ANS: (d)

31. Use of  Grashoff’s number is in

1. Free convection

2. Forced convection

3. Free & forced convection

4. None

ANS: (a)

32. Expression for Grashoff’s number is

1. Firstly        βgρL³/µ²

2. Secondly    βgρ²L³/µ²

3. Thirdly        βgρ²L³Δt/µ²

4. None

ANS: (c )

33. The Grashoff’s number is the ratio of

1. Firstly          Viscous force/Buoyancy force

2. Secondly     Buoyancy force/viscous force

3. Thirdly         Buoyancy force/Viscous force²

4. None

ANS: (b)

34. The role of Grashoff’s number in free convection is same as

1. Firstly Reynolds number in free convection

2. Secondly Reynolds number in forced convection

3. Thirdly Reynolds number in free & forced convection

4. None

ANS: (b)

35. Use of Reynolds number is in

1. Free convection

2. Forced convection

3. Free & forced convection

4. None

ANS: (b)

36. The Nusselt number is the ratio of

1. Conductive heat transfer/convective heat transfer

2. Convective heat transfer/Conductive heat transfer

3. (Convective +conductive) heat transfer/4

4. None

ANS: (b)

37. The equation for Nusselt number is

1. Firstly    h L/µ

2. Secondly  h k/L

3. Thirdly      h L/k

4. None

ANS: (c )

38. Use of Nusselt number is to determine

1. Thermal conductivity

2. Convective heat transfer coefficient

3. Thermal conductivity & convective heat transfer coefficient

4. None

ANS; (b)

39. Use of Nusselt number is in

1. Free convective heat transfer

2. Forced convective heat transfer

3. Both free & forced convective heat transfer

4. None

ANS: (c )

40. The Nusselt number is the ratio of

1. Conductive heat transfer/Convective heat transfer

2. Convective heat transfer/Conductive heat transfer

3. Both (a) & (b)

4. None

ANS: (b)

41. In free convective heat transfer, Nusselt number is a function of

1. Firstly          Nu =f(Re, Pr)

2. Secondly     Nu = f (Re, Gr)

3. Thirdly           Nu = f(Gr, Pr)

4. None

ANS: (c )

42. In forced convective heat transfer, Nusselt number is a function of

1. Firstly          Nu= f(Re, Pr, Gr)

2. Secondly     Nu= f(Re, Gr)

3. Thirdly          Nu = f(Gr, Pr)

4. None

ANS: (a)

43. Equation of Rayleigh’s number is

1. Firstly          Ra = Gr Re

2. Secondly     Ra= Gr Pr

3. Thirdly         Ra =Re Pr

4. None

ANS: (b)

44. Use of Rayleigh’s number is in

1. Free convection

2. Forced convection

3. Free & forced convection

4. None

ANS: (a)

     45. Froude number is

1. Firstly   Viscous force/Inertia force

2. Inertia force/Gravitational force

3. Viscous force/Pressure force

4. None

ANS: (b)

     46. Fluid flow is critical when Froude number is

1. > 1

2. < 1

3. = 1

4. None

ANS: (c )

     47. Fluid flow is super-critical when Froude number is

1. > 1

2. < 1

3. = 1

4. None

ANS: (a)

     48. Fluid flow is sub-critical when Froude number is

1. > 1

2. < 1

3. = 1

4. None

 ANS: (b)

     49. Fluid flow is critical when the ratio of flow velocity and wave velocity due to a disturbance is

1. > 1

2. < 1

3. = 1

4. None

ANS: (c )

     50. Weber number is used in

1. Single phase flow

2. Multi-phase flow

3. Single & multi-phase flow

4. None

ANS: (b)

     51. Weber number is used in the formation of

1. Droplets

2. Bubbles

3. Droplets & bubbles

4. None

ANS: ( c)

     52. Weber number is the ratio of the square root of

1. Inertia force/Gravitational force

2. Inertia force/ Surface tension

3. Both (a) & (b)

4. None

ANS: (b)

     53. Formula of Weber number is square root of

1. V/√Lg

2. V√ρL / √σ

3. V²/ √ρσ

4. None

ANS: (b)

     54. Critical Weber number at which

1. Firstly  Droplets start breaking

2. Secondly Droplets starts forming

3. Thirdly Droplets starts breaking & forming

4. None

ANS: (c )

     55. Mach number is the ratio of

1. Firstly Speed of object in a fluid/sound velocity in the same fluid

2. Secondly  Speed of object in air/speed of sound in water

3. Thirdly Speed of object in air/ velocity of light

4. None

ANS: (a)

     56. Minimum value of Mach number used practically

1. > 1

2. <1

3. < 0.3

4. None

ANS: (c )

     57. For sub-sonic flow, Mach number is

1. < 0.3

2. <0.8

3. > 1

4. None

 

      ANS: (b)

 

     58. For super-sonic flow, range of Mach number is

1. 10 to 25

2. 0 to 10

3. 3 to 5.0

4. None

ANS: (c )

     59. For hyper-sonic flow, the Mach number range is

1. 3 to 5.0

2. 0 to 10.0

3. 10 to 25

4. None

ANS: (b)

     60. Common use of Mach number is in

1. Railway

2. Bus

3. Aircraft

4. None

ANS: (c )

     61. What is velocity at Mach number equal to 1?

1. 1035 km/h

2. 1135 km/h

3. 1235 km/h

4. None

ANS: (c )

     62. Euler number in fluid mechanics is

1. Inertia force/pressure force

2. Pressure force/inertia force

3. Both (a) & (b)

4. None

ANS: (b)

     63. The formula for Euler number is

1. µ/ρv²

2. p/ρv

3. p/ρv²

4. None

ANS: (c )

     64. Euler number equal to 1 represents

1. Viscous flow

2. Non- viscous flow

3. Both viscous & non- viscous flow

4. None

ANS: (b)

     65. Euler number is

1. Pressure/(mass x acceleration)

2. Pressure x area/(mass x velocity)

3. Pressure x area/mass x acceleration)

4. None

ANS: (c )

     66. Ratio of inertia force to elastic force is

1. Mach number

2. Reynolds number

3. Froude number

4. None

ANS: (a)

https://mesubjects.net/wp-admin/post.php?post=655&action=edit      Dimensionless numbers class notes

https://mesubjects.net/wp-admin/post.php?post=14160&action=edit   MCQ ON DIMENSIONAL ANALYSIS