31. Thermal conductivity of glass-wool varies from sample to sample because of variation in
(a) composition
(b) density
(c) porosity
(d) structure
(e) all of the above.
Ans: e
32. 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
(e) none of the above.
Ans: d
33. Which of the following has maximum value of thermal conductivity
(a) aluminium
(b) steel
(c) brass
(d) copper
(e) lead.
Ans: a
34. Moisture would find its way into insulation by vapour pressure unless it is prevented by
(a) high thickness of insulation
(b) high vapour pressure
(c) less thermal conductivity insulator
(d) a vapour seal
(e) all of the above.
Ans: d
35. 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) refrigerator condenser coils
(e) boiler.
Ans: e
36. 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
(e) rate of heat transfer depends on thermal conductivity and temperature difference.
Ans: c
37. The ratio of heat flow Q1/Q2 from two walls of same thickness having their thermal conductivities as ATj - 2K2 will be
(a) I
(b) 0.5
(c) 2
(d) 0.25
(e) 4.0
Ans: c
38. 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
(e) none of the above.
Ans: d
39. Thermal diffusivity is
(a) a dimensionless parameter
(b) function of temperature
(c) used as mathematical model
(d) a physical property of the material
(e) useful in case of heat transfer by radiation.
Ans: d
40. Thermal diffusivity of a substance is .
(a) proportional of thermal conductivity
(b) inversely proportional to k
(c) proportional to (kf
(d) inversely proportional to k2
(e) none of the above.
Ans: a
Read More Questions:
Heat Transfer - Mechanical MCQs Part1
Heat Transfer - Mechanical MCQs Part2
(a) composition
(b) density
(c) porosity
(d) structure
(e) all of the above.
Ans: e
32. 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
(e) none of the above.
Ans: d
33. Which of the following has maximum value of thermal conductivity
(a) aluminium
(b) steel
(c) brass
(d) copper
(e) lead.
Ans: a
34. Moisture would find its way into insulation by vapour pressure unless it is prevented by
(a) high thickness of insulation
(b) high vapour pressure
(c) less thermal conductivity insulator
(d) a vapour seal
(e) all of the above.
Ans: d
35. 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) refrigerator condenser coils
(e) boiler.
Ans: e
36. 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
(e) rate of heat transfer depends on thermal conductivity and temperature difference.
Ans: c
37. The ratio of heat flow Q1/Q2 from two walls of same thickness having their thermal conductivities as ATj - 2K2 will be
(a) I
(b) 0.5
(c) 2
(d) 0.25
(e) 4.0
Ans: c
38. 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
(e) none of the above.
Ans: d
39. Thermal diffusivity is
(a) a dimensionless parameter
(b) function of temperature
(c) used as mathematical model
(d) a physical property of the material
(e) useful in case of heat transfer by radiation.
Ans: d
40. Thermal diffusivity of a substance is .
(a) proportional of thermal conductivity
(b) inversely proportional to k
(c) proportional to (kf
(d) inversely proportional to k2
(e) none of the above.
Ans: a
Read More Questions:
Heat Transfer - Mechanical MCQs Part1
Heat Transfer - Mechanical MCQs Part2
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