# Heat and Mass Transfer MCQ – Set 07

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## Q1. When α is absorptivity, ρ is reflectivity and τ is transmissivity, then for a diathermanous body,

(A) α = 1, ρ = 0 and τ = 0
(B) α = 0, ρ = 1 and τ = 0
(C) α = 0, ρ = 0 and τ = 1
(D) α + ρ = 1 and τ = 0

## Q2. Sensible heat factor is given by (where S.H. = Sensible heat, and L.H. = Latent heat)

(A) S.H/(S.H + L.H)
(B) (S.H + L.H) /S.H
(C) (L.H – S.H)/S.H
(D) S.H/(L.H – S.H)

## Q3. Wien’s law states that the wave length corresponding to __ is proportional to the absolute temperature.

(A) Minimum energy
(B) Maximum energy
(C) Both (A) and (B)
(D) None of these

## Q4. The amount of radiation mainly depends upon the

(A) Nature of the body
(B) Temperature of the body
(C) Type of surface of the body
(D) All of these

## Q5. The rate of energy transferred by convection to that by conduction is called

(A) Stanton number
(B) Nusselt number
(C) Biot number
(D) Peclet number

## Q6. Two plates spaced 150 mm apart are maintained at 1000°C and 70°C. The heat transfer will take place mainly by

(A) Convection
(C) Forced convection
(D) Free convection

## Q7. 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

## Q8. The energy distribution of an ideal reflector at higher temperatures is largely in the range of

(A) Shorter wavelength
(B) Longer wavelength
(C) Remain same at all wavelengths
(D) Wavelength has nothing to do with it

## Q9. The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body. This statement is known as

(A) Kirchoff’s law
(B) Stefan’s law
(C) Wien’ law
(D) Planck’s law

(A) Conduction
(B) Convection
(D) Scattering

## Q11. Thermal conductivity of wood depends on

(A) Moisture
(B) Density
(C) Temperature
(D) All of the above

## Q12. Absorptivity of a body will be equal to its emissivity

(A) At all temperatures
(B) At one particular temperature
(C) When system is under thermal equilibrium
(D) At critical temperature

## Q13. The process of heat transfer from one particle of the fluid to another by the actual movement of the fluid particles caused by some mechanical means, is known as

(A) Conduction
(B) Free convection
(C) Forced convection

## Q14. The most commonly used method for the design of duct size is the

(A) Velocity reduction method
(B) Equal friction method
(C) Static regains method
(D) Dual or double method

## Q15. Radiation is the process of heat transfer in which heat flows from a __, in a straight line, without affecting the intervening medium.

(A) Cold body to hot body
(B) Hot body to cold body
(C) Smaller body to larger body
(D) Larger body to smaller body

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