Lakshya Education MCQs

Question: Thermal diffusivity of a substance is given by (where h = thermal diffusivity, ρ = density of substance, s = specific heat, and k = thermal conductivity)
Options:
A. h = k/ ρS
B. h = ρS/k
C. h = S/ρk
D. h = kρ/S
Answer: Option A
Explanation :

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More Questions on This Topic :

Question 1. Wien’s law states that the wave length corresponding to ________ is proportional to the absolute temperature.
  1.     Minimum energy
  2.     Maximum energy
  3.     Both (A) and (B)
  4.     None of these
Answer: Option B
Explanation :
Question 2. The amount of radiation mainly depends upon the
  1.     Nature of the body
  2.     Temperature of the body
  3.     Type of surface of the body
  4.     All of these
Answer: Option D
Explanation :
Question 3. The emissive power of a body depends upon its
  1.     Temperature
  2.     Wave length
  3.     Physical nature
  4.     All of the above
Answer: Option D
Explanation :
Question 4. In convection heat transfer from hot flue gases to water tube, even though flow may be turbulent, a laminar flow region (boundary layer of film) exists close to the tube. the heat transfer through this film takes place by
  1.     Convection
  2.     Radiation
  3.     Conduction
  4.     Both convection and conduction
Answer: Option C
Explanation :
Question 5. The amount of radiation mainly depends on
  1.     Nature of body
  2.     Temperature of body
  3.     Type of surface of body
  4.     All of the above
Answer: Option D
Explanation :
Question 6. The heat transfer by conduction through a thick cylinder (q) is given by (where t₁ = higher temperature, t₂ = lower temperature, r₁ = inside radius, r₂ = outside radius, l = length of cylinder, and k = thermal conductivity)
  1.     Q = [2πlk (T₁ - T₂)]/2.3 log (r₂/r₁)
  2.     Q = 2.3 log (r₂/r₁)/[2πlk (T₁ - T₂)]
  3.     Q = [2π (T₁ - T₂)]/2.3 lk log (r₂/r₁)
  4.     Q = = 2πlk/2.3 (T₁ - T₂) log (r₂/r₁)
Answer: Option A
Explanation :

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