## According to Prevost theory of heat exchange ___________________?

A. it is impossible to transfer heat from low temperature source to t high temperature source
B. heat transfer by radiation requires no medium
C. all bodies above absolute zero emit radiation
D. heat transfer in most of the cases takes place by combination of conduction, convection and radiation
E. rate of heat transfer depends on thermal conductivity and temperature difference

A. 0.45
B. 0.55
C. 0.40
D. 0.75
E. 0.60

## According to Stefan-Boltzmann law, ideal radiators emit radiant energy at a rate proportional to___________________?

A. absolute temperature
B. square of temperature
C. fourth power of absolute temperature
D. fourth power of temperature
E. cube of absolute temperature

A. liquids
B. energy
C. temperature
D. entropy
E. enthalpy

## In free con-vection heat transfer, Nusselt number is function of________________?

A. Grashoff no. and Reynold no
B. Grashoff no and Prandtl no.
C. Prandtl no. and Reynold no
D. Grashoff no., Prandtl no and Reynold no
E. none of the above

## Thermal conductivity of air with rise in temperature__________________?

A. increases
B. decreases
C. remains constant
D. may increase or decrease depending on temperature
E. none of the above

## Joule sec is the unit of_________________?

A. universal gas constant
B. kinematic viscosity
C. thermal conductivity
D. Planck’s constant
E. none of the above

## According to Stefan’s law, the total radiation from a black body per second per unit area is proportional to____________________?

A. absolute temperature
B. T2
C. T5
D. t
E. l/T

## The emissive power of a body depends upon its___________________?

A. temperature
B. wave length
C. physical nature
D. all of the above
E. none of the above

A. 0.002
B. 0.02
C. 0.01
D. 0.1
E. 0.5

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