Download PDF
Free download in PDF Heat Multiple Choice Questions & Answers for competitive exams. These objective type questions are very important for competitive exams like IIT-JEE, NEET, AIIMS, JIPMER etc. These short solved questions or quizzes are provided by Gkseries.
(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
(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
(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
(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
(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
(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
(11)
Cork is a good insulator because it has
[A]
free electrons
[B]
atoms colliding frequency
[C]
low density
[D]
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
(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
(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
(19)
Heat transfer in liquid and gases takes place by
[A]
conduction
[B]
convection
[C]
radiation
[D]
conduction and convection
(20)
Heat is closely related with
[A]
liquids
[B]
energy
[C]
temperature
[D]
entropy
Take Mock Tests