Heat MCQs | Heat Multiple Choice Questions with Answers

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Questions
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

Answer: thickness
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

Answer: 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

Answer: increases
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

Answer: 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

Answer: 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

Answer: 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

Answer: 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

Answer: lower
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

Answer: 1 : 2
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

Answer: higher
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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