heat transfer MCQs – Page 5

Practise focused heat transfer questions with marked answers for exam preparation and subject revision.

heat transfer Mcqs
81. A grey body is one whose absorptivity _________________?
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A. varies with the wave length of incident ray

B. there is no such criterion

C. varies with both

D. varies with temperature

E. does not vary with temperature and wave length of the incident ray
82. The unit of Stefan Boltzmann constant is ____________________?
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A. watt/cm4 K

B. watt2/cm K4

C. watt/cm2 K4

D. watt/cm2 K2

E. watt/cm2 K

83. Depending on the radiating properties, a body will be black when_________________?
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A. p = 0, x = 0 and a = 1

B. x = 0, a + p = 0

C. p= l,T = 0anda = 0

D. p = 0, x = 1 and a = 0

E. a = 0,x + p= 1.

F. re a = absorptivity, p == reflectivity, X = transmissivity

84. Log mean temperature difference in case of counter flow compared to parallel flow will be________________?
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A. less

B. same

C. more

D. depends on other factors

E. none of the above

85. The thermal diffusivities for solids are generally__________________?
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A. zerci

B. less than those for gases

C. more than those for liquids and gases

D. more or less same as for liquids and gases

E. jess than those for liquids

86. Depending on the radiating properties, body will be transparent when________________?
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A. a = 0,x + p= 1

B. p = 0, T= l,anda = 0

C. p = 0, x = 0 and a = 1

D. p=l,x = 0,anda = 0

E. X = 0, a + p = 1

87. Joule sec is the unit of_________________?
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A. universal gas constant

B. Plancks constant

C. none of the above

D. kinematic viscosity

E. thermal conductivity

88. Absorptivity of a body will be equal to its emissivity___________________?
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A. at all temperatures

B. at one particular temperature

C. at critical temperature

D. for a polished body

E. when system is under thermal equi-librium
89. Plancks law holds good for________________?
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A. all coloured bodies

B. polished bodies

C. none of the above

D. all of the above

E. black bodies
90. The amount of radiation mainly depends on___________________?
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A. none of the above

B. temperature of body

C. all of the above

D. type of surface of body

E. nature of body

91. Thermal diffusivity of a substance is __________________?
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A. inversely proportional to density of substance

B. inversely proportional to specific heat

C. directly proportional to thermal conductivity

D. all of the above

E. none of the above

92. The energy distribution of an ideal reflector at higher temperatures is largely in the range of ___________________?
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A. longer wavelength

B. wavelength has nothing to do with it

C. none of the above

D. shorter wavelength

E. remains same at all wavelengths