What is the equivalent emissivity for radiant heat exchange between a small body (emissivity = 0.in a very large enclosure (emissivity = 0.5)?
  • a) 0.5
  • b) 0.4
  • c) 0.2
  • d) 0.1
If a body is at 2000K, the wavelength at which the body emits maximum amount of radiation is __________
  • a) 1.45µm
  • b) 1.45cm
  • c) 0.345cm
  • d) 0.345µm
Which of the following parameter is not responsible for loss of heat from a hot surface in room?
  • a) Temperature of the surface
  • b) Emissivity of the surface
  • c) Temperature of the air in the room
  • d) Dimensions of the room
Hot coffee in a cup is allowed to cool. Its cooling rate is measured and found to be greater than the value calculated by conduction, convection and radiation measurement. The difference is due to:
  • a) Properties of coffee changing with temperature
  • b) Currents of air flow in the room
  • c) Underestimation of the emissivity of coffee
  • d) Evaporation
Which of the following statement is incorrect?
  • a) For metals, the value of absorptivity is high
  • b) For non-conducting materials, reflectivity is low
  • c) For polished surfaces, reflectivity is high
  • d) For gases, reflectivity is very low
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