RADIATION EXCHANGE MULTIPLE CHOICE QUESTIONS (MCQ) WITH ANSWERS
RADIATION EXCHANGE
MULTIPLE CHOICE QUESTIONS
(MCQ) WITH ANSWERS
MCQ increase knowledge and clarity
about a topic. Shape factors depend upon
the geometry and orientation of the surfaces.
Number of shape factors for n bodies is n^{2}.
Find shape factors from shape factor
algebra and graphs. These help to find the
radiation exchange between two bodies. MCQ
help to apply shape factors in real life applications.
Radiation exchange is controllable. It greatly
depends upon the size, orientation,
medium in between, distance and
emissivity of surfaces.
Fig. Radiant Heat Exchange Between Two Nonblack Parallel Infinite Surfaces
Fig. Shape Factors For Aligned Parallel Surfaces
Fig. Shape factors between two rectangular surfaces at right angles
1. Radiation shape factor is also

Geometrical factor

Configuration Or View factor

(a) & (b)

None
ANS: (c )

Shape factor depends upon

Firstly Geometry and orientation of emitting surface

Secondly Geometry & orientation of collecting surface

(a) & (b)

None
ANS: (c )

Symbol for shape factor for black bodies is

F_{ij}

f_{ij}

(a) & (b)

None
ANS: (a)

Shape factor F_{ij} is

Firstly Direct radiations from body2 on body 1/Total radiations emitted by body 2

Secondly Direct radiations from body1 on body 2/Total radiations emitted by body 1

Thirdly Direct radiations from body2 on body 1/Total radiations emitted by body 1

None
ANS:(b)

Find shape factors from

Shape factor algebra

Graphs

(a) & (b)

None
ANS: (c )

Use graphs to find shape factors for

Parallel surfaces

Perpendicular surfaces

Parallel & perpendicular surfaces

None
ANS: (c )

Utility of shape factor is in finding radiation exchange between

Two surfaces

Three surfaces

Any number of surfaces

None
ANS: (c )

Find shape factor easily for

Simple shapes

Complex shapes

Simple & complex shapes

None
ANS: (a)

How to find shape factor for complex geometries?

Directly from the graphs

Dividing the complex shape into simple shapes

Both (a) & (b)

None
ANS: (b)

How many shape factors are there between ‘n’ bodies?

Firstly n^{3}

Secondly n

Thirdly n^{2}

None
ANS: (c )

Shape factor algebra is

Sum of shape factors

Difference of shape factors

Interrelation between shape factors

None
ANS: (c )

Find shape factors using

Law of summation

Law of reciprocity & la of energy conservation

From (a ) & (b)

None
ANS: (c )

Law of summation between two surfaces is

Firstly F_{11}+F_{12}+F_{22}+ F_{21} =0

Secondly F_{11}+F_{12}+F_{22}+ F_{21} =1

Both (a) & (b)

None
ANS: (d)

Law of summation between body 1 and body 2 is

Firstly F_{11}+F_{12} =1

Secondly F_{21}+F_{22}=1

Both (a) & (b)

None
ANS: (c )

Law of reciprocity between body 1 and 2 is

Firstly A_{1}F_{11}=A_{2} F_{22}

Secondly A_{1}F_{12}=A_{2} F_{22}

Thirdly A_{1}F_{11}=A_{2} F_{21}

None
ANS: (d)

Law of summation is applicable for

Two bodies

Three bodies

n bodies

None
ANS: (c )

Law of reciprocity is applicable between

Two bodies

Three bodies

n bodies

None
ANS: (a)

Shape factors F11, F22, F33—for flat bodies is

Zero

1

2

None
ANS: (a)

Shape factor for a convex surface is

Zero

1

2

None
ANS: (a)

Shape factor for a concave surface is

Zero

Non zero

3

None
ANS: (b)

Shape factor between two grey bodies is

F_{12}

f_{12}

Both (a) & (b)

None
ANS: (b)

Interchange factor f_{12 }for two infinite parallel surfaces is given as

Firstly 1/(1/€_{1}+1/€_{2})

Secondly 1/(1/€_{1}+1/€_{2} 1)

Thirdly 1/(1/€_{1}+1/€_{2} + 1)

None
ANS: (b)

Shape factor between two long concentric cylinders is

Firstly 1/(1/€_{1}+1/€_{2})

Secondly 1/[(1/€_{1}+(A_{2}/A_{1})(1/€_{2})]

Thirdly 1/[(1/€_{1}+(A_{1}/A_{2}(1/€_{2} 1)]

None
ANS: (c)

Shape factor between two small grey bodies is

Firstly 1/(1/€_{1}+1/€_{2})

Secondly 1/€_{1}€_{2}

Thirdly €_{1}€_{2}

None
ANS: (c )

Shape factor for body 1 completely enclosed by body 2, body 1 is small

1/€_{1}€_{2}

€_{1}€_{2}

€_{1}

None
ANS: (c )

Shape factor for body 1 completely enclosed by body 2, body 1 is large size

1/€_{1}€_{2}

€_{1}€_{2}

€_{1}

None
ANS: (d )

Shape factor for body 1 completely enclosed by body 2, body 1 is small

Firstly 1/(1/€_{1}+1/€_{2})

Secondly 1/[(1/€_{1}+(A_{2}/A_{1})(1/€_{2})]

Thirdly 1/[(1/€_{1}+(A_{1}/A_{2}(1/€_{2} 1)]

None
ANS: (c )
28. One of the methods used to find the shape factor is
(a) Law of difference
(b) Law of summation
(c) Law of multiplication
(d) None
ANS: (b)
29. Number of shape factors for 3 bodies is


(a) 3 x 1

(b) 3 x 2

(c) 3 x 3

(d) None

ANS: ©
30. Law of summation for 3 bodies is
(a) F12+F21+F13=1
(b) F33+F31+F13=1
(c) F11+F21+F13=1
(d) None
ANS: (d)
31. Law of Reciprocity states
(a) A1 F12 = A2 F22
(b) A1F12 = A2 F21
(c) F11+F12 =1
(d) None
ANS: (b)
31. Value of the shape factor F12 for a small body 1 enclosed in a big body 2 is
(a) < 1
(b) >1
(c) =1
(d) None
ANS: ©
32. Radiation between nonblack surfaces depends upon

Radiative properties & temperatures

Geometry and orientations

Both (a) & (b)

None
ANS: (c )
33. Radiation exchange between black surfaces depends upon

Radiative properties & temperatures

Temperatures & shape factors

Both (a) & (b)

None
ANS: (b)
34. Radiation exchange between two black surfaces 1 and 2 given as
(a) A_{1}F_{21}σ_{b} (T_{1}^{4}T_{2}^{4}) OR A_{2}F_{12}σ_{b} (T_{1}^{4}T_{2}^{4})
(b) A_{1}F_{12}σ_{b} (T_{1}^{4}T_{2}^{4}) OR A_{2}F_{21}σ_{b} (T_{1}^{4}T_{2}^{4})
(c) A_{1}F_{21}σ_{b} (T_{1}^{4}T_{2}^{4}) + A_{1}F_{12}σ_{b} (T_{1}^{4}T_{2}^{4})
(d) None
ANS: (b)
35. Assumption used in radiation exchange between surfaces is

Surfaces separated by participating mediums

Surfaces separated by nonparticipating medium

Both (a) & (b)

None
ANS: (b)
36. A nonparticipating medium which do not

Emits

Absorbs

Emits & absorbs

None
ANS: (c )
37. Practical example of nonparticipating medium is

Water vapors

Carbon dioxide

Other gases

None
ANS: (c )
38.Practical example of participating medium is

Water vapors

Carbon dioxide

Both water vapors & carbon dioxide

None
ANS: (c )
39. Radiation exchange is studied with

Electrical network approach

Radiation shields

Both (a) & (b)

None
ANS: ©
40. Radiation exchange between two black bodies is

Complex

Simple

Both simple & complex

None
ANS: (b)
41. Electrical network approach requires

Radiosity

Irradiation

Both radiosity & irradiation

None
ANS: (c )
42. Nonblack bodies for radiation exchange are

Transparent

Opaque

Both opaque & transparent

None
ANS: (b)
43. Radiosity is

Firstly Sum of transmitted and emitted radiations/m^{2}s

Secondly Sum of transmitted & reflected radiations/m^{2}s

Thirdly Sum of emitted & reflected radiations/m^{2}s

None
ANS: (c )
44. Irradiation is

Firstly Total reflected radiant energy/m^{2}s

Secondly Total radiant incident radiations/m^{2}s

Thirdly Total reflected & incident radiations/m^{2}s

None
ANS: b)
45. The symbol for radiosity is

G

J

E

None
ANS: (b)
46. The symbol for irradiation is

G

J

E

None
ANS: (a)
Fig. Surface and Space Resistances between two radiating Surfaces
Fig. Surface & Space Resistances Between Three Bodies Not in a line
47. Surface resistance for a nonblack body is

(1€)/€

€/(1€)

(1€)/€A

None
ANS: (c )
48. Space resistance is

Firstly 1/A_{1}F_{11}

Secondly 1/A_{1}F_{12}

Thirdly 1/A_{2}F_{12}

None
ANS: (b)
49. How many surface and space resistances between two nonblack bodies?

1,3

2,2

2,4

None
ANS: (b)
50. How many surface resistances and space resistances between two black bodies?

Firstly 0, 3

Secondly 0, 4

Thirdly 0,2

None
ANS: (c )
51. To reduce radiation exchange between two bodies, use a

Radiosity

Radiation shield

Irradiation

None
ANS: (b)
52. Radiation shield is a

Transparent body

Opaque body

Black body

None
ANS: (b)
53. A radiation shield has

High absorptivity & high reflectivity

High transmissivity & high reflectivity

Low absorptivity & high reflectivity

None
ANS: (c )
54. Preferable radiation shield is thin sheet of

Copper or aluminum

Steel or cast iron

Paper or board

None
ANS: (a)
55. Radiation exchange between two infinite parallel nonblack bodies is

Firstly Q_{12}=Aσ_{b}(T_{1}^{4}—T_{2}^{4})/(1/€_{1})

Secondly Q_{12}=Aσ_{b}(T_{1}^{4}—T_{2}^{4})/(1/€_{1} +1/€_{2} +1)

Thirdly Q_{12}=Aσ_{b}(T_{1}^{4}—T_{2}^{4})/(1/€_{1}+ 1/€_{2}–1)

None
ANS: (c )
56. Radiation exchange between two nonblack parallel infinite surfaces & radiation shield of same emissivity is as compared to without radiation shield is

1/3

¼

1/6

None
ANS: (d)
57. Radiation exchange between two nonblack parallel infinite surfaces & radiation shield of same emissivity is as compared to without radiation shield is

1/2

1/3

1/4

None
ANS: (a)
58. With €1=€2=€ _{shield}, the temperature of the radiation shield is

T_{1}^{4} +T_{2}^{4}

(1/3)( T_{1}^{4} +T_{2}^{4})

(1/2)( T_{1}^{4} +T_{2}^{4})

None
ANS: (c )
59. With n shields in between two nonblack parallel surfaces with same emissivity, €1=€2=€ _{shields}, the radiation exchange is
(a) (1/n) [A σ_{b }(T_{1}^{4} –T_{2}^{4})/((2/€)–1))]
(b) (1/(n+1)) [A σ_{b }(T_{1}^{4} –T_{2}^{4})/((2/€)–1))]
© (1/(n1)) [A σ_{b }(T_{1}^{4} –T_{2}^{4})/((2/€)–1))]
(d) None
ANS: (b)
60. How many space resistances with n shields in between two nonblack parallel radiating surfaces?

n

n1

n+1

None
ANS: (c)
61. How many surface resistances with n shields in between two nonblack parallel radiating surfaces?

n+2

n2

n+1

None
ANS: (a)
62. . The expression for radiosity is

(a) ρα + ϵ E_{b}

(b) ρα — ϵ E_{b}

(c) ρG+ ϵE_{b}

(d) None
ANS: ©
63. Radiosity equals emissive power for a
(a) Grey body
(b) White body
(c) Red body
(d) None
ANS: (d)
64. Number of Radiation shields of same emissivity reducing radiation exchange by one half.
(a) 1
(b) 2
(c) 3
(d) None
ANS: (a)
65. Radiosity ‘J’ for a black body is equal to the
(a) ρG+ ϵE_{b}
(b) E_{b}
(c) ϵE_{b}
(d) None
ANS: (b)
66. Radiation exchange between two grey bodies is given by
(a) (E_{g1} – E_{g2})/[(1ϵ_{1})/ϵ_{1} A_{1}) + 1/A_{1} F_{12} + (1ϵ_{2})/ϵ_{2} A_{2})]
(b) (E_{b1} – E_{b2})/[(1ϵ_{1})/ϵ_{1} A_{1}) + 1/A_{1} F_{12} + (1ϵ_{2})/ϵ_{2} A_{2})]
(c) (E_{g1} – E_{g2})/[(1/ϵ_{1} + + 1/ϵ_{2} –1]
(d) None
ANS: (b)
67. Surface resistance for a black body is
(a) Twice of a same size grey body
(b) Same as for a same size grey body
(c) Zero
(d) None
ANS: (c)
68. Space resistance depends on
(a) Distance between the two bodies
(b) Size & Orientation of the two bodies with respect to each other
(c) (a) & (b)
(d) None
ANS: (c )
https://mesubjects.net/wpadmin/post.php?post=14170&action=edit MCQ RADIATION BASICS
https://www.mesubjects.net/wpadmin/post.php?post=264&action=edit Radiation Exchange Class Notes