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

Related Mcqs:

1. The total emissivity power is .defined as the total amount of radiation emitted by a black body per unit_______________?

   A. temperature
   B. thickness
   C. area
   D. time
   E. area and time

2. 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

3. Stefan Boltzmann law is applicable for heat transfer by __________________?

   A. conduction
   B. convection
   C. radiation
   D. conduction and radiation combined
   E. convection and radiation combined

4. The unit of Stefan Boltzmann constant is ____________________?

   A. watt/cm2 °K
   B. watt/cm4 °K
   C. watt2/cm °K4
   D. watt/cm2 °K4
   E. watt/cm2 °K2

5. 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

6. Emissivity of a white polished body in comparison to a black body is________________?

   A. higher
   B. lower
   C. same
   D. depends upon the shape of body
   E. none of the above

7. Total emissivity of polished silver compared to black body is___________________?

   A. same
   B. higher
   C. more or less same
   D. very much lower
   E. very much higher

8. All radiations in a black body are___________________?

   A. reflected
   B. refracted
   C. transmitted
   D. absorbed
   E. partly reflected and partly absorbed

9. Depending on the radiating properties, a body will be black when_________________?

   A. p = 0, x = 0 and a = 1
   B. p= l,T = 0anda = 0
   C. p = 0, x = 1 and a = 0
   D. x = 0, a + p = 0
   E. a = 0,x + p= 1.
   where a = absorptivity, p == reflectivity, X = transmissivity

10. 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_________________?

    A. Krichoff’s law
    B. Stefan’s law
    C. Wien’ law
    D. Planck’s law
    E. Black body law