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Free download in PDF Heat Multiple Choice Questions with 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.
61
Pick up the wrong case. Heat flowing from one side to other depends directly on
[A]
face area
[B]
time
[C]
thickness
[D]
temperature difference
62
Which of the following is a case of steady state heat transfer
[A]
I.C. engine
[B]
air preheaters
[C]
heating of building in winter
[D]
none of the above
Answer: none of the above
63
Thermal conductivity of water in general with rise in temperature
[A]
increases
[B]
decreases
[C]
remains constant
[D]
may increase or decrease depending on temperature
Answer: may increase or decrease depending on temperature
64
Temperature of steam at around 540°C can be measured by
[A]
thermometer
[B]
radiatiouv pyrometer
[C]
thermistor
[D]
thermocouple
65
Thermal conductivity of air with rise in temperature
[A]
increases
[B]
decreases
[C]
remains constant
[D]
may increase or decrease depending on temperature
66
The concept of overall coefficient of heat transfer is used in heat transfer problems of
[A]
conduction
[B]
convection
[C]
radiation
[D]
conduction and comte_ction
Answer: conduction and comte_ction
67
Thermal conductivity of a material may be defined as the
[A]
quantity of heat flowing in one second through one cm cube of material when opposite faces ^re maintained at a temperature difference of 1°C
[B]
quantity of heat flowing in one second through a slab of the material of area one cm square, thickness 1 cm when its faces differ in temperature by 1°C
[C]
heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maintained between opposite faces
[D]
all of the above
68
Heat is transferred by all three modes of transfer, viz, conduction, convection and radiation in
[A]
electric heater
[B]
steam condenser
[C]
melting of ice
[D]
boiler
69
According to Prevost theory of heat exchange
[A]
it is impossible to transfer heat from low temperature source to t high temperature source
[B]
heat transfer by radiation requires no medium
[C]
all bodies above absolute zero emit radiation
[D]
heat transfer in most of the cases takes place by combination of conduction, convection and radiation
Answer: all bodies above absolute zero emit radiation
70
Heat transfer by radiation mainly depends upon
[A]
its temperature
[B]
nature of the body
[C]
kind and extent of its surface
[D]
all of the above
71
Thermal diffusivity of a substance is .
[A]
proportional of thermal conductivity
[B]
inversely proportional to k
[C]
proportional to (k)
[D]
inversely proportional to k2
Answer: proportional of thermal conductivity
72
Thermal conductivity of wood depends on
[A]
moisture
[B]
density
[C]
temperature
[D]
all of the above
73
Film coefficient is defined as Inside diameter of tube
[A]
Equivalent thickness of film
[B]
Thermal conductivity Equivalent thickness of film Specific heat x Viscocity
[C]
Thermal conductivity Molecular diffusivity of momentum Thermal diffusivity
[D]
Film coefficient x Inside diameter Thermalconductivity
Answer: Thermal conductivity Equivalent thickness of film Specific heat x Viscocity
74
The rate of energy emission from unit surface area through unit solid angle, along a normal to the surface, is known as
[A]
emissivity
[B]
transmissivity
[C]
reflectivity
[D]
intensity of radiation
Answer: intensity of radiation
75
Emissivity of a white polished body in comparison to a black body is
[A]
higher
[B]
lower
[C]
same
[D]
depends upon the shape of body
76
Two balls of same material and finish have their diameters in the ratio of 2 : 1 and both are heated to same temperature and allowed to cool by radiation. Rate of cooling by big ball as compared to smaller one will be in the ratio of
[A]
1 :1
[B]
2: 1
[C]
1 : 2
[D]
4 : 1
77
LMTD in case of counter flow heat exchanger as compared-to parallel flow heat exchanger is
[A]
higher
[B]
lower
[C]
same
[D]
depends on the area of heat exchanger
78
In heat exchangers, degree of approach is defined as the difference between temperatures of
[A]
cold water inlet and outlet
[B]
hot medium inlet and outlet
[C]
hot medium outlet and cold water inlet
[D]
hot medium outlet and cold water outlet
Answer: hot medium outlet and cold water outlet
79
A steam pipe is to be insulated by two insulating materials put over each other. For best results
[A]
better insulation should be put over pipe and better one over it
[B]
inferior insulation should be put over pipe and better one over it
[C]
both may be put in any order
[D]
whether to put inferior OIL over pipe or the better one would depend on steam temperature
Answer: better insulation should be put over pipe and better one over it
80
According of Kirchhoff's law,
[A]
radiant heat is proportional to fourth power of absolute temperature
[B]
emissive power depends on temperature
[C]
emissive power and absorptivity are constant for all bodies
[D]
ratio of emissive power to absorptive power for all bodies is same and is equal to the emissive power of a perfectly black body.
Answer: ratio of emissive power to absorptive power for all bodies is same and is equal to the emissive power of a perfectly black body.
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