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Heat MCQs | Heat Multiple Choice Questions with Answers

Questions
1 Unit of thermal conductivity in M.K.S. units is
A kcal/kg m2 °C
B kcal-m/hr m2 °C
C kcal/hr m2 °C
D kcal-m/hr °C

Answer: kcal-m/hr m2 °C
2 Thermal conductivity of solid metals with rise in temperature normally
A increases
B decreases
C remains constant
D may increase or decrease depending on temperature

Answer: decreases
3 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

Answer: does not vary with temperature and wave length of the incident ray
4 A perfect black body is one which
A is black in colour
B reflects all heat
C transmits all heat radiations
D abslprbs heat radiations of all wave lengths falling on it

Answer: abslprbs heat radiations of all wave lengths falling on it
5 Two plates spaced 150 mm apart are maintained at 1000°C and 70°C. The heat transfer will take place mainly by
A convection
B free convection
C forced convection
D radiation

Answer: radiation
6 40% of incident radiant energy on the surface of a thermally transparent body is reflected back. If the transmissivity of the body be 0.15, then the emissivity of surface is
A 0.45
B 0.55
C 0.40
D 0.75

Answer: 0.45
7 Depending on the radiating properties, a body will be black when
A p = 0, x = 0 and a = 1
B p= l,T = 0anda = 0
C p = 0, x = 1 and a = 0
D x = 0, a + p = 0

Answer: p = 0, x = 0 and a = 1
8 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

Answer: t
9 The amount of heat flow through a body by conduction is
A directly proportional to the surface area of the body
B directly proportional to the temperature difference on the two faces of the body
C dependent upon the material of the body
D all of the above

Answer: all of the above.
10 Thermal conductivity of air at room temperature in kcal/m hr °C is of the order of
A 0.002
B 0.02
C 0.01
D 0.1

Answer: 0.02
11 Cork is a good insulator because it has
A free electrons
B atoms colliding frequency
C low density
D porous body

Answer: porous body
12 Which of the following is the case of heat transfer by radiation
A blast furnace
B heating of building
C cooling of parts in furnace
D heat received by a person from fireplace

Answer: heat received by a person from fireplace
13 The insulation ability of an insulator with the presence of moisture would
A increase
B decrease
C remain unaffected
D may increase/decrease depending on temperature and thickness of insulation

Answer: decrease
14 When heat is transferred from one particle of hot body to another by actual motion of the heated particles, it is referred to as heat transfer by
A conduction
B convection
C radiation
D conduction and convection

Answer: conduction
15 Unit of thermal conductivity in S.I. units is
A J/m2 sec
B J/m °K sec
C W/m °K
D (b) and (c) above

Answer: (b) and (c) above
16 Heat transfer takes place as per -
A zeroth law of thermodynamics
B first law of thermodynamic
C second law of the thermodynamics
D Kirchoff's law

Answer: second law of the thermodynamics
17 Sensible heat is the heat required to
A change vapour into liquid
B change liquid into vapour
C increase the temperature of a liquid of vapour
D convert water into steam and superheat it

Answer: increase the temperature of a liquid of vapour
18 When heat is Transferred by molecular collision, it is referred to as heat transfer by
A conduction
B convection
C radiation
D scattering

Answer: convection
19 Heat transfer in liquid and gases takes place by
A conduction
B convection
C radiation
D conduction and convection

Answer: convection
20 Heat is closely related with
A liquids
B energy
C temperature
D entropy

Answer: temperature

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