Heat and Mass Transfer - Set 08 - ObjectiveBooks

# Practice Test: Question Set - 08

1. The thermal diffusivities for solids are generally
(A) Less than those for gases
(B) Less than those for liquids
(C) More than those for liquids and gases
(D) More or less same as for liquids and gases

2. Depending on the radiating properties, body will be transparent when
(Where a = absorptivity, p = reflectivity, x = transmissivity)
(A) P = 0, x = 0 and a = 1
(B) P=1, x = 0, and a = 0
(C) P = 0, T= 1, and a = 0
(D) X = 0, a + p = 1

3. Thermal diffusivity of a substance is
(A) Directly proportional to thermal conductivity
(B) Inversely proportional to density of substance
(C) Inversely proportional to specific heat
(D) All of the above

4. 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

5. 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

6. 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

7. According to Stefan's law, the total radiation from a black body per second per unit area is proportional to
(A) Absolute temperature
(B)
(C) T⁵
(D) T

8. The heat transfer from a hot body to a cold body is directly proportional to the surface area and difference of temperatures between the two bodies. This statement is called
(A) First law of thermodynamics
(B) Newton's law of cooling
(C) Newton's law of heating
(D) Stefan's law

9. According to Wien's law, the wavelength corresponding to maximum energy is proportion to
(A) Absolute temperature (T)
(B)
(C) F
(D) T

10. The process of heat transfer from one particle of the body to another by the actual motion of the heated particles, is called
(A) Conduction
(B) Convection
(D) None of these

11. Depending on the radiating properties, a body will be white when
(Where a = absorptivity, p = reflectivity, x = transmissivity)
(A) P = 0, x = 0 and a = 1
(B) P=1, T = 0 and a = 0
(C) P = 0, x = 1 and a = 0
(D) X = 0, a + p = 1

12. A steam pipe is to be lined with two layers of insulating materials of different thermal conductivities. For the minimum heat transfer,
(A) The better insulation must be put inside
(B) The better insulation must be put outside
(C) One could place either insulation on either side
(D) One should take into account the steam temperature before deciding as to which insulation is put where

13. Depending on the radiating properties, a body will be black when
(Where a = absorptivity, p = reflectivity, X = transmissivity.)
(A) P = 0, x = 0 and a = 1
(B) P= 1, T = 0 and a = 0
(C) P = 0, x = 1 and a = 0
(D) X = 0, a + p = 0

14. The process of heat transfer from one particle of the fluid to another by the actual movement of the fluid particles due to difference of density caused by temperature of the particle is known as
(A) Conduction
(B) Free convection
(C) Forced convection