Planck’s law holds good for________________?

Related Mcqs:

1. Fourier’s law of heat conduction is valid for_________________?

   A. one dimensional cases only
   B. two dimensional cases only
   C. three dimensional cases only
   D. regular surfaces having non-uniform temperature gradients
   E. irregular surfaces

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. 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

4. 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

5. 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

6. 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

7. Thermal conductivity of non-metallic amorphous solids with decrease in temperature __________________?

   A. increases
   B. decreases
   C. remains constant
   D. may increase or decrease depending on temperature
   E. unpredictable

8. Cork is a good insulator because it has___________________?

   A. free electrons
   B. atoms colliding frequency
   C. low density
   D. porous body
   E. all of the above

9. Moisture would find its way into insulation by vapour pressure unless it is prevented by __________________ ?

   A. high thickness of insulation
   B. high vapour pressure
   C. less thermal conductivity insulator
   D. a vapour seal
   E. all of the above

10. A steam pipe is to be insulated by two insulating materials put over each other . For best results__________________?

    A. better insulation should be put over pipe and better one over it
    B. inferior insulation should be put over pipe and better one over it
    C. both may be put in any order
    D. whether to put inferior OIL over pipe or the better one would depend on steam temperature
    E. unpredictable