Stefan-Boltzmann law which describes the radiation heat transfer states that, it is proportional to (where, t = temperature in °C T = absolute temperature in ° K) ?

Related Mcqs:

1. Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer across an equal area held at the________________?

   A. Surrounding temperature
   B. Average temperature of the fin
   C. Temperature of the fin end
   D. Constant temperature equal to that of the base

2. Stefan-Boltzmann law applies to _____________ body?

   A. Black
   B. White
   C. Grey
   D. Any colour

3. The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m2. The approximate surface temperature (K) is (Stefan-Boltzmann constant = 5.67 × 10-8 W/m2.K4) ?

   A. 1000
   B. 727
   C. 800
   D. 1200

4. Stefan’s block body radiation law can also be derived from ______________ law?

   A. Kirchoff’s
   B. Planck’s
   C. Fourier’s
   D. None of these

5. The Stefan-Boltzmann constant depends on the_________________?

   A. Medium
   B. Temperature
   C. Surface
   D. None of these

6. The value of Stefan-Boltzmann constant in SI unit is_________________?

   A. 5.6697 × 10-8W/m2.°K4
   B. 0.1714 × 10-8W/m2.°K4
   C. 5.6697 × 10-8kcal/m2. °K4
   D. 0.1714 × 10-8kcal/m2. °K4

7. A 10 cm dia steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m2.°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be__________________?

   A. Greater than that for un-insulated steam pipe
   B. Less than that of the un-insulated steam pipe
   C. Equal to that of the un-insulated steam pipe
   D. Less than the steam pipe with 5 cms insulation

8. For small temperature difference, the heat transfer rate as per Newton’s law of cooling is proportional to (where, Δt = excess temperature) ?

   A. Δt
   B. Δt2
   C. Δt3
   D. √(Δt)

9. With increase in the distance between the heat source and the object receiving the heat, the radiation heat transfer ?

   A. Decreases
   B. Increases
   C. Increases exponentially
   D. Remain unaffected

10. The thermal radiation emitted by a body is proportional to Tn, where T is its absolute temperature. The value of ‘n’ is exactly 4 for__________________?

    A. Black painted bodies only
    B. All bodies
    C. Polished bodies only
    D. A black body