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Mechanical Engineering Objective Questions { Heat Transfer }



50. Which of the following has least value of conductivity
A.Glass
B.Air
C.Plastic
D.Rubber

51. Depending on the radiating properties, body will be transparent when
A.? = 0, ? = 0 and ? = 1
B.? = 1, ? = 0 and ? = 0
C.? = 0, ? = 1 and ? = 0
D.? = 0, ?+? = 1

52. The concept of overall coefficient of heat transfer is used in case of heat transfer by
A.Conduction
B.Convection
C.Radiation
D.Conduction and convection

53. Two plates spaced 150 mm apart are maintained at 1000C and 70C. The heat transfer will take place mainly by
A.Convection
B.Free convection
C.Forced convection
D.Radiation

54. Thermal conductivity of glass-wool varies from sample to sample because of variation in
A.Composition
B.Porosity
C.Structure
D.All of the above

55. 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 are maintained at a temperature difference of 1C
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 1C
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

56. Which of the following has maximum value of thermal conductivity
A.Aluminium
B.Steel
C.Brass
D.Copper

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