Heat Multiple Choice Questions with Answers

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

View Answer

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

View Answer

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

View Answer

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

View Answer

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

View Answer

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

View Answer

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

View Answer

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

View Answer

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

View Answer

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

View Answer

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

View Answer

Answer: proportional of thermal conductivity

72 Thermal conductivity of wood depends on

A moisture

B density

C temperature

D all of the above

View Answer

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

View Answer

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

View Answer

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

View Answer

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

View Answer

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

View Answer

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

View Answer

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

View Answer

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.

View Answer

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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