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

Related Mcqs:

1. 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

2. 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

3. 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

4. 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

5. 40% of incident radiant energy on the surface of a thermally transparent body is reflected back. If the transmissivity of the body be 0.15, then the emissivity of surface is____________________?

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

6. The amount of radiation mainly depends on___________________?

   A. nature of body
   B. temperature of body
   C. type of surface of body
   D. all of the above
   E. none of the above

7. All radiations in a black body are___________________?

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

8. A perfect black body is one which_______________?

   A. is black in colour
   B. reflects all heat
   C. transmits all heat radiations
   D. abslprbs heat radiations of all wave lengths falling on it
   E. fully opaque

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 amount of heat flow through a body by conduction is_______________?

    A. directly proportional to the surface area of the body
    B. directly proportional to the temperature difference on the two faces of the body
    C. dependent upon the material of the body
    D. inversely proportional to the thickness of the body
    E. all of the above