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) T²
- (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) I²
- (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
- (C) Radiation
- (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
- (D) Radiation
15. A grey body is one whose absorptivity
- (A) Varies with temperature
- (B) Varies with the wave
length of incident ray
- (C) Varies with both
- (D) Does not vary with
temperature and wave length of the incident ray
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