A grey body is one whose absorptivity _________________?

Related Mcqs:

1. A grey body is one whose absorptivity_________________?

   A. varies with temperature
   B. varies with wavelength of the incident ray
   C. is equal to its emissivity
   D. does not vary with temperature and. wavelength of the incident ray
   E. none of the above

2. 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

3. Absorptivity of a body will be equal to its emissivity___________________?

   A. at all temperatures
   B. at one particular temperature
   C. when system is under thermal equi-librium
   D. at critical temperature
   E. for a polished body

4. Depending on the radiating properties, a body will be opaque when _________________?

   A. p = 0, x = 0 and a = 1
   B. p=l,x = 0anda = 0
   C. p = 0, x = 1 and a = 0
   D. x – 0, a + p = 1
   E. a=0,x + p= 1.

   where a = absorptivity, p = reflectivity, X = transmissivity

5. When heat is transferred form hot body to cold body, in a straight line, without affecting the intervening medium, it is referred as heat transfer by __________________?

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

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. 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

8. Heat is transferred by all three modes of transfer, viz, conduction, convection and radiation in _________________?

   A. electric heater
   B. steam condenser
   C. melting of ice
   D. refrigerator condenser coils
   E. boiler

9. LMTD in case of counter flow heat exchanger as compared-to parallel flow heat exchanger is _________________?

   A. higher
   B. lower
   C. same
   D. depends on the area of heat exchanger
   E. depends on temperature conditions

10. 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