Heat Transfer

1. Define Lagging

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2. Name the two mechanisms of thermal conduction in metals

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3. Explain how a spoon dipped in hot water shortly gets hot at the free end?

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4. Radiation is the flow of heat from one place to another by means of electromagnetic waves?

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5. Between a white car and a black car which one will absorb more heat than the other when you place both cars in an open field at 12 noon in Mombasa?

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6. Is the temperature difference between the ends of the conductor a factor affecting its thermal conductivity?

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7. Thermal equilibrium is when 2 bodies at the same temperature are in contact and there is no heat flow?

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8. Gases are the worst conductors of heat because of large inter-molecular distance?

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9. Which of the following is not among the factors affecting thermal conductivity?

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10. Explain why steam pipes in industry are lagged with poor conductors of heat

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11. Which of the following is NOT a mode of heat transfer?

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12. Thermal conductivity depends on the nature of the material (metal) such as iron and copper?

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13. Which of the following is the main difference between metals and non-metals?

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14. Rate of heat flow increases or decreases according to the nature of material?

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15. DEFINE heat

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16. Convection currents move faster in

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17. Rate of heat flow is directly proportional to the temperature difference. True or False?

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18. How is heat transferred from the sun to the earth?

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19. Is water a poor conductor of heat?

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20. Convection is:

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21. Metals are good conductors of heat?

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22. Which of the following is not an application of convection in fluids

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23. Black (dull) materials are better emitters of heat than white (shiny/polished) material?

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24. Conduction can take place in solids?

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25. Which of the following is not a property of the radiant heat from the sun?

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26. Which of one the following explains why Liquids are poor conductor of heat?

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27. Thermal conductivity increases as you increase in cross-section area of a material?

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28. Rate of heat flow is inversely proportional to the length of a conductor. True or False?

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29. Explain why a copper rod gets hot earlier than an iron rod of the same shape and size and all put in the same heat source

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30. Why are electrolytes better conductors of heat than pure liquid?

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31. Explain reason why warm water in a heated sufuria rises and replaced by cold water from the top?

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32. Non-metals are poor conductors of heat?

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33. Rate of heat flow is directly proportional to cross-section area of a conductor. True or False?

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34. SI UNIT of heat is?

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35. What makes Radiation mode of heat transfer different from conduction and convection?

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36. Why are exhaust pipes in a ship covered with thick asbestos material?

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37. Different metals have different thermal conductivities

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38. Black materials are better absorbers of heat than white material?

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39. Which of the following describes an application of thermal radiation?

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40. When you heat water in a sufuria what happens?

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41. A body emitting thermal radiation can also emit visible light when it is hot enough?

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42. What is the name given when you mix hot and cold parts of the fluid using external stirring such as fan or pump?

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43. Thermal conductivity increases as you decrease the length of a metal (material)?

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44. Conduction can take place in liquid and gases?

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