Heating and Welding

11. Heat is transferred simultaneously by condition, convection and radiation

  1. inside boiler furnaces
  2. during melting of ice
  3. through the surface of the insulted pipe carrying steam
  4. from refrigerator coils to freezer of a refrigerator

Correct answer: (A)
inside boiler furnaces

12. The process of heat transfer during the reentry of satellites and missiles, at very high speeds, into earth’s atmosphere is known as

  1. ablation
  2. radiation
  3. viscous dissipation
  4. irradiation

Correct answer: (A)

13. Which of the following has the highest value of thermal conductivity?

  1. Water
  2. Steam
  3. Solid ice
  4. Melting ice

Correct answer: (C)
Solid ice

14. Induction heating process is based on which of the following principles?

  1. Thermal ion release principle
  2. Nucleate heating principle
  3. Resistance heating principle
  4. Electro-magnetic induction principle

Correct answer: (D)
Electro-magnetic induction principle

15. Which of the following insulating materials was suitable for low temperature applications?

  1. Asbestos paper
  2. Diatomaceous earth
  3. 80 percent magnesia
  4. Cork

Correct answer: (B)
Diatomaceous earth

16. A non-dimensional number generally associated with natural convection heat transfer is

  1. Prandtl number
  2. Grashoff number
  3. Pecelet number
  4. Nusselt number

Correct answer: (B)
Grashoff number

17. The temperature inside a furnace is usually measured by which of the following?

  1. Optical pyrometer
  2. Mercury thermometer
  3. Alcohol thermometer
  4. Any of the above

Correct answer: (A)
Optical pyrometer

18. Which of the following will happen if the thickness of refractory wall of furnace is increased?

  1. Heat loss through furnace wall will increase
  2. Temperature inside the furnace will fall
  3. Temperature on the outer surface of furnace walls will drop
  4. Energy consumption will increase

Correct answer: (C)
Temperature on the outer surface of furnace walls will drop

19. The material of the heating element for a furnace should have

  1. lower melting point
  2. higher temperature coefficient
  3. high specific resistance
  4. all of the above

Correct answer: (C)
high specific resistance

20. In a resistance furnace the atmosphere is

  1. oxidising
  2. deoxidising
  3. reducing
  4. neutral

Correct answer: (A)

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