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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 n2.

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 Non-black 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

  1. Geometrical factor

  2. Configuration Or View factor

  3. (a) & (b)

  4. None

ANS: (c )

  1. Shape factor depends upon

  1. Firstly Geometry and orientation of emitting surface

  2. Secondly Geometry & orientation of collecting surface

  3. (a) & (b)

  4. None

ANS: (c )

  1. Symbol for shape factor for black bodies is

  1. Fij

  2. fij

  3. (a) & (b)

  4. None

ANS: (a)

  1. Shape factor Fij is

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

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

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

  4. None

ANS:(b)

  1. Find shape factors from

  1. Shape factor algebra

  2.  Graphs

  3. (a) & (b)

  4. None

ANS: (c )

  1. Use graphs to find shape factors for

  1. Parallel surfaces

  2. Perpendicular surfaces

  3. Parallel & perpendicular surfaces

  4. None

ANS: (c )

  1. Utility of shape factor is in finding radiation exchange between

  1. Two surfaces

  2. Three surfaces

  3. Any number of surfaces

  4. None

ANS: (c )

  1. Find shape factor easily for

  1. Simple shapes

  2. Complex shapes

  3. Simple & complex shapes

  4. None

ANS: (a)

  1. How to find shape factor for complex geometries?

  1. Directly from the graphs

  2. Dividing the complex shape into simple shapes

  3. Both (a) & (b)

  4. None

ANS: (b)

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

  1. Firstly n3

  2. Secondly n

  3. Thirdly n2

  4. None

ANS: (c )

  1. Shape factor algebra is

  1. Sum of shape factors

  2. Difference of shape factors

  3. Inter-relation between shape factors

  4. None

ANS: (c )

  1. Find shape factors using

  1. Law of summation

  2. Law of reciprocity & la of energy conservation

  3. From (a ) & (b)

  4. None

ANS: (c )

  1. Law of summation between two surfaces is

  1. Firstly         F11+F12+F22+ F21 =0

  2. Secondly    F11+F12+F22+ F21 =1

  3. Both (a) & (b)

  4. None

ANS: (d)

  1. Law of summation between body 1 and body 2 is

  1. Firstly      F11+F12 =1

  2. Secondly   F21+F22=1

  3. Both (a) & (b)

  4. None

ANS: (c )

  1. Law of reciprocity between body 1 and 2 is

  1. Firstly          A1F11=A2 F22

  2. Secondly     A1F12=A2 F22

  3. Thirdly         A1F11=A2 F21

  4. None

ANS: (d)

  1. Law of summation is applicable for

  1. Two bodies

  2. Three bodies

  3. n bodies

  4. None

ANS: (c )

  1. Law of reciprocity is applicable between

  1. Two bodies

  2. Three bodies

  3. n bodies

  4. None

ANS: (a)

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

  1. Zero

  2. 1

  3. 2

  4. None

ANS: (a)

  1. Shape factor for a convex surface is

  1. Zero

  2. 1

  3. 2

  4. None

ANS: (a)

  1. Shape factor for a concave surface is

  1. Zero

  2. Non zero

  3. 3

  4. None

ANS: (b)

  1. Shape factor between two grey bodies is

  1. F12

  2. f12

  3. Both (a) & (b)

  4. None

ANS: (b)

  1. Interchange factor f12 for two infinite parallel surfaces is given as

  1. Firstly      1/(1/€1+1/€2)

  2. Secondly   1/(1/€1+1/€2 -1)

  3. Thirdly       1/(1/€1+1/€2 + 1)

  4. None

ANS: (b)

  1. Shape factor between two long concentric cylinders is

  1. Firstly       1/(1/€1+1/€2)

  2. Secondly   1/[(1/€1+(A2/A1)(1/€2)]

  3. Thirdly       1/[(1/€1+(A1/A2(1/€2 -1)]

  4. None

ANS: (c)

  1. Shape factor between two small grey bodies is

  1. Firstly       1/(1/€1+1/€2)

  2. Secondly    1/€12

  3. Thirdly         €12

  4. None

ANS: (c )

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

  1. 1/€12

  2. 12

  3. 1

  4. None

ANS: (c )

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

  1. 1/€12

  2. 12

  3. 1

  4. None

ANS: (d )

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

  1. Firstly              1/(1/€1+1/€2)

  2. Secondly         1/[(1/€1+(A2/A1)(1/€2)]

  3. Thirdly             1/[(1/€1+(A1/A2(1/€2 -1)]

  4. 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 non-black surfaces depends upon

  1. Radiative properties & temperatures

  2. Geometry and orientations

  3. Both (a) & (b)

  4. None

ANS: (c )

     33. Radiation exchange between black surfaces depends upon

  1. Radiative properties & temperatures

  2. Temperatures & shape factors

  3. Both (a) & (b)

  4. None

ANS: (b)

     34. Radiation exchange between two black surfaces 1 and 2 given as

  (a) A1F21σb (T14-T24) OR A2F12σb (T14-T24)

    (b) A1F12σb (T14-T24) OR A2F21σb (T14-T24)

(c)  A1F21σb (T14-T24) + A1F12σb (T14-T24)

(d) None

ANS: (b)

     35. Assumption used in radiation exchange between surfaces is

  1. Surfaces separated by participating mediums

  2. Surfaces separated by non-participating medium

  3. Both (a) & (b)

  4. None

ANS: (b)

     36. A non-participating medium which do not

  1. Emits

  2. Absorbs

  3. Emits & absorbs

  4. None

ANS: (c )

     37. Practical example of non-participating medium is

  1. Water vapors

  2. Carbon dioxide

  3. Other gases

  4. None

ANS: (c )

    38.Practical example of participating medium is

  1. Water vapors

  2. Carbon dioxide

  3. Both water vapors & carbon dioxide

  4. None

ANS: (c )

     39. Radiation exchange is studied with

  1. Electrical network approach

  2. Radiation shields

  3. Both (a) & (b)

  4. None

ANS: ©

     40. Radiation exchange between two black bodies is

  1. Complex

  2. Simple

  3. Both simple & complex

  4. None

ANS: (b)

     41. Electrical network approach requires

  1. Radiosity

  2. Irradiation

  3. Both radiosity & irradiation

  4. None

ANS: (c )

     42. Non-black bodies for radiation exchange are

  1. Transparent

  2. Opaque

  3. Both opaque & transparent

  4. None

ANS: (b)

     43. Radiosity is

  1. Firstly    Sum of transmitted and emitted radiations/m2s

  2. Secondly    Sum of transmitted & reflected radiations/m2s

  3. Thirdly    Sum of emitted & reflected radiations/m2s

  4. None

ANS: (c )

     44. Irradiation is

  1. Firstly Total reflected radiant energy/m2s

  2. Secondly Total radiant incident radiations/m2s

  3. Thirdly Total reflected & incident radiations/m2s

  4. None

ANS: b)

     45. The symbol for radiosity is

  1. G

  2. J

  3. E

  4. None

ANS: (b)

     46. The symbol for irradiation is

  1. G

  2. J

  3. E

  4. 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 non-black body is

  1. (1-€)/€

  2. €/(1-€)

  3. (1-€)/€A

  4. None

ANS: (c )

     48. Space resistance is

  1. Firstly     1/A1F11

  2. Secondly      1/A1F12

  3. Thirdly        1/A2F12

  4. None

ANS: (b)

     49. How many surface and space resistances between two non-black bodies?

  1. 1,3

  2. 2,2

  3. 2,4

  4. None

ANS: (b)

     50. How many surface resistances and space resistances between two black bodies?

  1. Firstly 0, 3

  2. Secondly 0, 4

  3. Thirdly   0,2

  4. None

ANS: (c )

     51. To reduce radiation exchange between two bodies, use a

  1. Radiosity

  2. Radiation shield

  3. Irradiation

  4. None

ANS: (b)

     52. Radiation shield is a

  1. Transparent body

  2. Opaque body

  3. Black body

  4. None

ANS: (b)

     53. A radiation shield has

  1. High absorptivity & high reflectivity

  2. High transmissivity & high reflectivity

  3. Low absorptivity & high reflectivity

  4. None

ANS: (c )

    54. Preferable radiation shield is thin sheet of

  1.  Copper or aluminum

  2.  Steel or cast iron

  3.  Paper or board

  4. None

ANS: (a)

     55. Radiation exchange between two infinite parallel non-black bodies is

  1. Firstly          Q12=Aσb(T14—T24)/(1/€1)

  2. Secondly    Q12=Aσb(T14—T24)/(1/€1 +1/€2 +1)

  3. Thirdly        Q12=Aσb(T14—T24)/(1/€1+ 1/€2–1)

  4. None

ANS: (c )

      56. Radiation exchange between two non-black parallel infinite surfaces & radiation shield  of same emissivity is as compared to without radiation shield is

  1. 1/3

  2. ¼

  3. 1/6

  4. None

ANS: (d)

     57. Radiation exchange between two non-black parallel infinite surfaces &  radiation shield  of same emissivity is as compared to without radiation shield is

  1. 1/2

  2. 1/3

  3. 1/4

  4. None

ANS: (a)

     58. With €1=€2=€ shield, the temperature of the radiation shield is

  1. T14 +T24

  2. (1/3)( T14 +T24)

  3. (1/2)( T14 +T24)

  4. None

ANS: (c )

     59. With n shields in between two non-black parallel surfaces with same emissivity, €1=€2=€ shields, the radiation exchange is

(a) (1/n) [A σb (T14 –T24)/((2/€)–1))]

(b) (1/(n+1)) [A σb (T14 –T24)/((2/€)–1))]

©  (1/(n-1)) [A σb (T14 –T24)/((2/€)–1))]

    (d) None

ANS: (b)

     60. How many space resistances with n shields in between two non-black parallel radiating surfaces?

  1. n

  2. n-1

  3. n+1

  4. None

ANS: (c)

     61. How many surface resistances with n shields in between two non-black parallel radiating surfaces?

  1. n+2

  2. n-2

  3. n+1

  4. None

ANS: (a)

62. . The expression for radiosity is

  • (a) ρα + ϵ Eb

  • (b) ρα — ϵ Eb

  • (c) ρG+ ϵEb

  • (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+ ϵEb

(b)  Eb

(c)  ϵEb

(d) None

ANS: (b)

    66. Radiation exchange between two grey bodies is given by

(a) (Eg1 – Eg2)/[(1-ϵ1)/ϵ1 A1) + 1/A1 F12 + (1-ϵ2)/ϵ2 A2)]

(b) (Eb1 – Eb2)/[(1-ϵ1)/ϵ1 A1) + 1/A1 F12 + (1-ϵ2)/ϵ2 A2)]

(c) (Eg1 – Eg2)/[(1/ϵ1 + + 1/ϵ2 –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 )

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