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

Biot number is applicable to

Conduction

Convection

Radiation

None
ANS: (a)

Biot number is applicable to

Steady state conduction

Unsteady state conduction

Steady & unsteady state conduction

None
ANS: (b)

Biot number is applicable to

Heat exchangers

Radiators

Fins

None
ANS: (c )

Biot number is the ratio of

Firstly Conductive resistance/Convective resistance

Secondly Convective resistance / Conductive resistance

Thirdly Convective resistance /Radiative resistance

None
ANS: (a)

Different ranges of Biot number

One

Two

Three

None
ANS: (c )

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

Lumped parameter method

Heisler charts method

Gauss Error function method

None
ANS: (a)

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

Lumped parameter method

Heisler charts method

Gauss Error function method

None
ANS: (b)

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

Lumped parameter method

Heisler charts

Gauss Error function method

None
ANS: (c)

Equation for Biot number is

hk/L

kL/h

hL/k

None
ANS: (c )

Fourier number is degree of penetration of

Heating in a solid

Cooling in a solid

Heating or cooling in a solid

None
ANS: (c )

Formula for Fourier number is

Firstly ατ/L

Secondly ατ/L^{2}

Thirdly ατ/L^{3}

None
ANS: (b)

Fourier number is applicable to

Conduction

Convection

Radiation

None
ANS: (a)

Fourier number is applicable to

Steady state conduction

Unsteady state conduction

Steady & unsteady state conduction

None
ANS: (b)

Fourier number is applicable to

Heat exchangers

Radiators

Fins

None
ANS: (c )

Reynolds number is the ratio of

Inertia force/Pressure force

Pressure force/Inertia force

Inertia force/viscous force

None
ANS: (c )

Reynolds number classify

Firstly Laminar & turbulent flows

Secondly Laminar & transition flows

Thirdly Laminar, transition & turbulent flows

None
ANS: (c )

The equation for Reynolds number is

ρv/D µ

Dρµ/v

ρvD/µ

None
ANS: ( c)

Reynolds number for laminar flow in a pipe is

Firstly < 1100

Secondly < 2100

Thirdly > 4000

None
ANS: (b)

Reynolds number for transition flow in a pipe is

Firstly < 1100 >2100

Secondly <2100 >3100

Thirdly > 2100 <4000

None
ANS: (c )

Reynolds number for turbulent flow in a pipe is

< 2100

<400

> 400

None
ANS: (c )

Reynolds number for transition flow over a flat plate is

Firstly > 2 Lacs <4 Lacs

Secondly > 4 Lacs <6 Lacs

Thirdly > 5 Lacs < 7 Lacs

None
ANS: (c )

Reynolds number for laminar flow over a flat plate is

Firstly ≤ 4 Lacs

Secondly ≤ 5 Lacs

Thirdly ≤ 6 lacs

None
ANS: (b)

Reynolds number for turbulent flow over a flat plate is

Firstly ≥ 5 Lacs

Secondly ≥ 7 Lacs

Thirdly ≥ 3 lacs

None
ANS: (b)

The ratio of inertia force to viscous force is

Fourier number

Nusselt number

Reynolds number

None
ANS: (c )

Prandtl number is the ratio of

Firstly Momentum diffusivity/ Thermal diffusivity

Secondly Momentum diffusivity/mass diffusivity

Thirdly Thermal diffusivity/Momentum diffusivity

None
ANS: (a)

The equation of Prandtl number is

µρ/k

k/ρc_{P}

µc_{p}/k

None
ANS: (c )

Use of Prandtl number is in

Free convection

Forced convection

Free & forced convection

None
ANS: (c )

Value of Prandtl number for liquid metals is

1 to 100

0.1 to 1

0.01 to 0.003

None
ANS: (c )

Value of Prandtl number for highly viscous oils is

0100

1001000

10010000

None
ANS: (c )

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

2 & 0.2

5 & 0.5

7 & 0.7

None
ANS: (d)

Use of Grashoff’s number is in

Free convection

Forced convection

Free & forced convection

None
ANS: (a)

Expression for Grashoff’s number is

Firstly βgρL^{3}/µ^{2}

Secondly βgρ^{2}L^{3}/µ^{2}

Thirdly βgρ^{2}L^{3}Δt/µ^{2}

None
ANS: (c )

The Grashoff’s number is the ratio of

Firstly Viscous force/Buoyancy force

Secondly Buoyancy force/viscous force

Thirdly Buoyancy force/Viscous force^{2}

None
ANS: (b)

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

Firstly Reynolds number in free convection

Secondly Reynolds number in forced convection

Thirdly Reynolds number in free & forced convection

None
ANS: (b)

Use of Reynolds number is in

Free convection

Forced convection

Free & forced convection

None
ANS: (b)

The Nusselt number is the ratio of

Conductive heat transfer/convective heat transfer

Convective heat transfer/Conductive heat transfer

(Convective +conductive) heat transfer/4

None
ANS: (b)

The equation for Nusselt number is

Firstly h L/µ

Secondly h k/L

Thirdly h L/k

None
ANS: (c )

Use of Nusselt number is to determine

Thermal conductivity

Convective heat transfer coefficient

Thermal conductivity & convective heat transfer coefficient

None
ANS; (b)

Use of Nusselt number is in

Free convective heat transfer

Forced convective heat transfer

Both free & forced convective heat transfer

None
ANS: (c )

The Nusselt number is the ratio of

Conductive heat transfer/Convective heat transfer

Convective heat transfer/Conductive heat transfer

Both (a) & (b)

None
ANS: (b)

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

Firstly Nu =f(Re, Pr)

Secondly Nu = f (Re, Gr)

Thirdly Nu = f(Gr, Pr)

None
ANS: (c )

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

Firstly Nu= f(Re, Pr, Gr)

Secondly Nu= f(Re, Gr)

Thirdly Nu = f(Gr, Pr)

None
ANS: (a)

Equation of Rayleigh’s number is

Firstly Ra = Gr Re

Secondly Ra= Gr Pr

Thirdly Ra =Re Pr

None
ANS: (b)

Use of Rayleigh’s number is in

Free convection

Forced convection

Free & forced convection

None
ANS: (a)
45. Froude number is

Firstly Viscous force/Inertia force

Inertia force/Gravitational force

Viscous force/Pressure force

None
ANS: (b)
46. Fluid flow is critical when Froude number is

> 1

< 1

= 1

None
ANS: (c )
47. Fluid flow is supercritical when Froude number is

> 1

< 1

= 1

None
ANS: (a)
48. Fluid flow is subcritical when Froude number is

> 1

< 1

= 1

None
ANS: (b)
49. Fluid flow is critical when the ratio of flow velocity and wave velocity due to a disturbance is

> 1

< 1

= 1

None
ANS: (c )
50. Weber number is used in

Single phase flow

Multiphase flow

Single & multiphase flow

None
ANS: (b)
51. Weber number is used in the formation of

Droplets

Bubbles

Droplets & bubbles

None
ANS: ( c)
52. Weber number is the ratio of the square root of

Inertia force/Gravitational force

Inertia force/ Surface tension

Both (a) & (b)

None
ANS: (b)
53. Formula of Weber number is square root of

V/√Lg

V√ρL / √σ

V^{2}/ √ρσ

None
ANS: (b)
54. Critical Weber number at which

Firstly Droplets start breaking

Secondly Droplets starts forming

Thirdly Droplets starts breaking & forming

None
ANS: (c )
55. Mach number is the ratio of

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

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

Thirdly Speed of object in air/ velocity of light

None
ANS: (a)
56. Minimum value of Mach number used practically

> 1

<1

< 0.3

None
ANS: (c )
57. For subsonic flow, Mach number is

< 0.3

<0.8

> 1
 None
ANS: (b)
58. For supersonic flow, range of Mach number is

10 to 25

0 to 10

3 to 5.0

None
ANS: (c )
59. For hypersonic flow, the Mach number range is

3 to 5.0

0 to 10.0

10 to 25

None
ANS: (b)
60. Common use of Mach number is in

Railway

Bus

Aircraft

None
ANS: (c )
61. What is velocity at Mach number equal to 1?

1035 km/h

1135 km/h

1235 km/h

None
ANS: (c )
62. Euler number in fluid mechanics is

Inertia force/pressure force

Pressure force/inertia force

Both (a) & (b)

None
ANS: (b)
63. The formula for Euler number is

µ/ρv^{2}

p/ρv

p/ρv^{2}

None
ANS: (c )
64. Euler number equal to 1 represents

Viscous flow

Non viscous flow

Both viscous & non viscous flow

None
ANS: (b)
65. Euler number is

Pressure/(mass x acceleration)

Pressure x area/(mass x velocity)

Pressure x area/mass x acceleration)

None
ANS: (c )
66. Ratio of inertia force to elastic force is

Mach number

Reynolds number

Froude number

None
ANS: (a)
https://mesubjects.net/wpadmin/post.php?post=655&action=edit Dimensionless numbers class notes
https://mesubjects.net/wpadmin/post.php?post=14160&action=edit MCQ ON DIMENSIONAL ANALYSIS