A. radiant heat is proportional to fourth power of absolute temperature
B. emissive power depends on temperature
C. emissive power and absorptivity are constant for all bodies
D. ratio of emissive power to absorptive power is maximum for perfectly black body
E. ratio of emissive power to absorptive power for all bodies is same and is equal to the emissive power of a perfectly black body
Related Mcqs:
- 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 - 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
E. none of the above - 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 - 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 - According to Wien’s law, the wavelength corresponding to maximum energy is proportion to ________________?
A. absolute temperature (T)
B. I2
C. f
D. t
E. 1/r - Which of the following is the case of heat transfer by radiation ___________________?
A. blast furnace
B. heating of building
C. cooling of parts in furnace
D. heat received by a person from fireplace
E. all of the above - Thermal conductivity of a material may be defined as the________________?
A. quantity of heat flowing in one second through one cm cube of material when opposite faces ^re maintained at a temperature difference of 1°C
B. quantity of heat flowing in one second through a slab of the material of area one cm square, thickness 1 cm when its faces differ in temperature by 1°C
C. heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maintained between opposite faces
D. all of the above
E. none of the above - Heat conducted througfi unit area and unit thick face per unit time when temperature difference between opposite faces is unity,is called__________________?
A. thermal resistance
B. thermal coefficient
C. temperature gradient
D. thermal conductivity
E. heat-transfer - The value of Prandtl number for air is about _______________________?
A. 0.1
B. 0.3
C. 0.7
D. 1.7
E. 10.5 - Two plates spaced 150 mm apart are maintained at 1000°C and 70°C. The heat transfer will take place mainly by ___________________?
A. convection
B. free convection
C. forced convection
D. radiation
E. radiation and convection
