Heat Transfer – LearnITbyTests

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

Conduction

Conviction

Radiation

Sublimation

Question 1 of 44

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

It produces light since it is extremely hot

It can be reflected since it is an electromagnetic wave

It can be concentrated to a point using a lens

It cannot cause heating effect.

Question 2 of 44

3. Metals are good conductors of heat?

True

False

Maybe

None

Question 3 of 44

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

Metals have free electrons which travel throughout the body of the metal

Heat energy imparted at the hot end of the metal spoon increases the vibration of the particles at the end.

The free electrons in the hot end gain kinetic energy and move spread heat energy to the free end.

All of the above

Question 4 of 44

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

Through conduction

Through radiation

Through thermal radiation

Through convection

Question 5 of 44

6. Conduction can take place in solids?

True

False

Maybe

None

Question 6 of 44

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

Metals use both atom vibration and free electrons to conduct heat

Non-metals use only atom vibration to conduct heat because they have no free electrons

Metals have immobile electrons and non-metals have free electrons

none of the above

Question 7 of 44

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

True

False

Maybe

None

Question 8 of 44

9. Conduction can take place in liquid and gases?

False

True

Maybe

None

Question 9 of 44

10. Name the two mechanisms of thermal conduction in metals

Atom vibrations and free (mobile) electron heat transfer

Immobile electrons and heat

Atom vibration and immobile electron

None

Question 10 of 44

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

It requires a medium for heat transfer to occur

It requires heat

It can take place in a vacuum

No idea

Question 11 of 44

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

False

True

Maybe

None

Question 12 of 44

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

The heated water expands and it lowers its density

The less dense water rises up

The denser colder water flows down and replaces it

All of the above

Question 13 of 44

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

Maybe

False

True

None

Question 14 of 44

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

Petrol tanks painted silvery bright to reflect away as much as heat as possible.

Houses and buildings in hot areas have their walls and roofs painted with bright/white colours to reflect away heat.

Sufurias, cooking pans and frying pans have polished surfaces to reduce heat loss through thermal radiation.

All of the above

Question 15 of 44

16. 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

Thermal conductivity is independent on the nature of the material

Thermal conductivity is dependent on the nature of the material

due to nature of material

Due to atom vibration and free electrons

Question 16 of 44

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

True

False

Maybe

None

Question 17 of 44

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

Natural

Natural convection

Forced

Forced convection

Question 18 of 44

19. 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?

Black car

White car

silver

None

Question 19 of 44

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

They have an increased compactness of the particles

They have a large intermolecular distance

They have rare collision between molecules

all of the mentioned

Question 20 of 44

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

Warm water rises

Cold water replaces it

water boils

Water melts

Question 21 of 44

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

FALSE

True

Maybe

None

Question 22 of 44

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

True

False

Maybe

None

Question 23 of 44

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

False

True

Maybe

None

Question 24 of 44

25. DEFINE heat

Is a form of power

A form of energy which passes from a body of higher temperature to a body of lower temperature.

A form of energy which passes from a body of lower temperature to a body of higher temperature.

Heat is rising temperature

Question 25 of 44

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

to reduce heat loss which will otherwise make the ship environment temperature high

to increase heat loss

for decoration purpose

none of the above

Question 26 of 44

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

True

False

Maybe

None

Question 27 of 44

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

Ventilation in a room

Car engine cooling system

Land and sea breeze

Starter motor in a car

Question 28 of 44

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

The nature of material

The length of conductor

The cross section area of the conductor

The weight of the material

Question 29 of 44

30. Non-metals are poor conductors of heat?

False

True

Maybe

None

Question 30 of 44

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

True

False

Maybe

None

Question 31 of 44

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

False

True

Maybe

None

Question 32 of 44

33. Convection currents move faster in

Solids

Liquids

Gas

molten state

Question 33 of 44

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

True

False

Maybe

None

Question 34 of 44

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

To increase heat loss

To reduce heat loss by conduction

Decorate the pipes

None

Question 35 of 44

36. Define Lagging

Is the covering of good conductors of heat with insulators

Is the covering of poor conductors of heat with good conductors

Is the covering of good conductors of heat with good conductors

No idea

Question 36 of 44

37. Is water a poor conductor of heat?

Maybe

False

True

None

Question 37 of 44

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

False

True

Maybe

None

Question 38 of 44

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

True

False

Maybe

None

Question 39 of 44

40. Different metals have different thermal conductivities

False

True

Maybe

None

Question 40 of 44

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

Yes

Maybe

None

Question 41 of 44

42. Convection is:

Process by which heat is transferred through liquid only

Process by which heat is transferred through gas only

Process by which heat is transferred through liquids and gases (fluids)

No idea

Question 42 of 44

43. SI UNIT of heat is?

Newton

Joules

Kelvin

degrees Celsius

Question 43 of 44

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

Liquids have their molecules far apart hence experience fewer collision between the molecules than solids.

Liquids have a small inter-molecular distance between liquid molecules

Liquid have zero molecules

Liquids are quick to pass heat to other regions than metals.

Question 44 of 44

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