Heat Transfer Multiple Choice Questions and Answers for Practice

16. Cork is a good insulator because it has

1. free electrons
2. atoms colliding frequency
3. low density
4. porous body

17. Which of the following has least value of conductivity

1. glass
2. water
3. plastic
4. air.

18. Moisture would find its way into insulation by vapour pressure unless it is prevented by

1. high thickness of insulation
2. high vapour pressure
3. less thermal conductivity insulator
4. a vapour seal

19. Which of the following is a case of steady state heat transfer

1. I.C. engine
2. air preheaters
3. heating of building in winter
4. none of the above.

20. The insulation ability of an insulator with the presence of moisture would

1. increase
2. decrease
3. remain unaffected
4. may increase/decrease depending on temperature and thickness of insulation

21. Thermal conductivity of solid metals with rise in temperature normally

1. increases
2. decreases
3. remains constant
4. may increase or decrease depending on temperature

22. Thermal conductivity of non-metallic amorphous solids with decrease in temperature

1. increases
2. decreases
3. remains constant
4. may increase or decrease depending on temperature

23. Thermal conductivity of water in general with rise in temperature

1. increases
2. decreases
3. remains constant
4. may increase or decrease depending on temperature

24. Thermal conductivity of air with rise in temperature

1. increases
2. decreases
3. remains constant
4. may increase or decrease depending on temperature

25. Heat transfer by radiation mainly depends upon

1. its temperature
2. nature of the body
3. kind and extent of its surface
4. all of the above

26. The thermal diffusivities for solids are generally

1. less than those for gases
2. jess than those for liquids
3. more than those for liquids and gases
4. more or less same as for liquids and gases

27. Heat is closely related with

1. liquids
2. energy
3. temperature
4. entropy

28. Thermal diffusivity of a substance is .

1. proportional of thermal conductivity
2. inversely proportional to k
3. proportional to (k)
4. inversely proportional to k2

29. All radiations in a black body are

1. reflected
2. refracted
3. transmitted
4. absorbed

30. Which of the following is expected to have highest thermal conductivity

1. steam
2. solid ice
3. melting ice
4. water