71. According of Kirchhoff's law

A.Radiant heat is proportional to fourth power of absolute temperature

B.Ratio of emissive power to absorptive power for all bodies is same and is equal to the emissive power of a perfectly black body

C.Emissive power and absorptivity are constant for all bodies

D.Ratio of emissive power to absorptive power is maximum for perfectly black body

72. According to Kirchoff's law, the ratio of emissive power to absorptivity for all bodies is equal to the emissive power of a

A.Grey body

B.Brilliant white polished body

C.Red hot body

D.Black body

73. Log mean temperature difference in case of counter flow compared to parallel flow will be

A.Same

B.More

C.Less

D.Depends on other factors

74. Joule sec is the unit of

A.Universal gas constant

B.Kinematic viscosity

C.Thermal conductivity

D.Planck's constant

75. Heat is closely related with

A.Liquids

B.Energy

C.Temperature

D.Entropy

76. The value of the wavelength for maximum emissive power is given by

A.Wien's law

B.Planck's law

C.Stefan's law

D.Fourier's law

77. Heat transfer in liquid and gases takes place by ?

A.Conduction

B.Convection

C.Radiation

D.Conduction and convection

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