74) Thermal diffusivity of a substance is

directly proportional to thermal con¬ductivity

inversely proportional to density of substance

inversely proportional to specific heat

all of the above

Answer is:

all of the above

Explanation:

Thermal diffusivity of a substance is
* directly proportional to the thermal conductivity
* inversely proportional to density of substance
* inversely proportional to specific heat

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75) The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body. This statement is known as

Krichoff′s law

Stefan′s law

Wien′ law

Planck′s law

Answer is:

Krichoff′s law

76) According to Stefan′s law, the total radiation from a black body per second per unit area is proportional to

absolute temperature

Answer is:

t

77) According to Wien′s law, the wavelength corresponding to maximum energy is proportion to

absolute temperature (T)

Answer is:

absolute temperature (T)

78) Depending on the radiating properties, a body will be white when

p = 0, x = 0 and a = 1

p=l,T = 0anda = 0

p = 0, x = 1 and a = 0

x = 0, a + p = 1where a = absorptivity, p = reflectivity, x = transmissivity

Answer is:

p=l,T = 0anda = 0

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74) Thermal diffusivity of a substance is

all of the above

Heat transfer MCQ with Answers

Related Heat transfer MCQ with Answers

75) The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body. This statement is known as

Krichoff′s law

76) According to Stefan′s law, the total radiation from a black body per second per unit area is proportional to

t

77) According to Wien′s law, the wavelength corresponding to maximum energy is proportion to

absolute temperature (T)

78) Depending on the radiating properties, a body will be white when

p=l,T = 0anda = 0

Heat transfer MCQ with Answers