Lakshya Education MCQs

Question: According to prevost theory of heat exchange
A. It is impossible to transfer heat from low temperature source to t high temperature source
B. Heat transfer by radiation requires no medium
C. All bodies above absolute zero emit radiation
D. Heat transfer in most of the cases takes place by combination of conduction, convection and radiation
Answer: Option C
Explanation :

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More Questions on This Topic :

Question 1. Which of the following has least value of conductivity?
  1.     Glass
  2.     Water
  3.     Plastic
  4.     Air
Answer: Option D
Explanation :
Question 2. A composite slab has two layers of different materials with thermal conductivities k₁ and k₂. if each layer has the same thickness, then the equivalent thermal conductivity of the slab will be
  1.     k₁ k₂
  2.     (k₁ + k₂)
  3.     (k₁ + k₂)/ k₁ k₂
  4.     2 k₁ k₂/ (k₁ + k₂)
Answer: Option D
Explanation :
Question 3. According to dalton's law of partial pressures, (where pb = barometric pressure, pa = partial pressure of dry air, and pv = partial pressure of water vapour)
  1.     Pb = pa - pv
  2.     Pb = pa + pv
  3.     Pb = pa × pv
  4.     Pb = pa/pv
Answer: Option B
Explanation :
Question 4. The unit of overall coefficient of heat transfer is
  1.     kcal/m²
  2.     kcal/hr °C
  3.     kcal/m² hr °C
  4.     kcal/m hr °C
Answer: Option C
Explanation :
Question 5. Unit of thermal conductivity in s.i. units is
  1.     J/m² sec
  2.     J/m °K sec
  3.     W/m °K
  4.     Option (B) and (C) above
Answer: Option D
Explanation :
Question 6. According to wien's law, the wavelength corresponding to maximum energy is proportion to
  1.     Absolute temperature (T)
  2.     I²
  3.     F
  4.     T
Answer: Option A
Explanation :

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