📘 Chapter 7 – Heat Transfer in Nature

🔹 Part 2: Convection (Q26–Q50)

Q26. Heat transfer in liquids and gases mainly takes place by:

A) Conduction
B) Convection
C) Radiation
D) Reflection

✅ Answer: B) Convection

Explanation:

• Solids → conduction.
• Liquids & gases → convection (Correct).
• Radiation → no medium required.
• Reflection → not heat transfer.

Q27. Convection involves:

A) Vibration of particles
B) Movement of particles
C) No particles
D) Radiation waves

✅ Answer: B) Movement of particles

Q28. Land breeze blows during:

A) Day
B) Night
C) Both
D) None

✅ Answer: B) Night

Explanation: At night, land cools faster, air above land moves towards the sea → land breeze.

Q29. Sea breeze blows during:

A) Day
B) Night
C) Both
D) None

✅ Answer: A) Day

Explanation: In daytime, land heats faster, air above land rises, cooler sea air moves in → sea breeze.

Q30. Which is an example of convection?

A) Heating of water in a pan
B) Heating iron rod
C) Heat from Sun
D) Reflection of light

✅ Answer: A) Heating of water in a pan

Q31. Which layer of air rises during convection?

A) Cold air
B) Hot air
C) Moist air only
D) No air rises

✅ Answer: B) Hot air

Explanation: Hot air is lighter (less dense) → rises.

Q32. Which air moves down during convection?

A) Hot air
B) Cool air
C) Moist air
D) None

✅ Answer: B) Cool air

Q33. The movement of air due to heating is called:

A) Convection current
B) Reflection
C) Radiation
D) Conduction

✅ Answer: A) Convection current

Q34. Convection is responsible for:

A) Sea and land breezes
B) Formation of winds
C) Heating water uniformly
D) All of these

✅ Answer: D) All of these

Q35. When water is heated from below, it circulates due to:

A) Conduction
B) Convection
C) Radiation
D) None

✅ Answer: B) Convection

Q36. Which process causes the smoke from a fire to rise upward?

A) Conduction
B) Convection
C) Radiation
D) Evaporation

✅ Answer: B) Convection

Q37. The breeze near a sea shore during day is:

A) Land to sea
B) Sea to land
C) Both ways
D) None

✅ Answer: B) Sea to land

Q38. Which of these is NOT due to convection?

A) Sea breeze
B) Land breeze
C) Winds
D) Heat transfer in solids

✅ Answer: D) Heat transfer in solids

Q39. Convection occurs in:

A) Solids only
B) Liquids only
C) Gases only
D) Liquids and gases

✅ Answer: D) Liquids and gases

Q40. The transfer of heat in the atmosphere causing winds is due to:

A) Conduction
B) Radiation
C) Convection
D) Evaporation

✅ Answer: C) Convection

Q41. Why does hot air balloon rise?

A) Hot air is heavier
B) Hot air is lighter
C) Cold air rises
D) None

✅ Answer: B) Hot air is lighter

Q42. Which property of liquids and gases makes convection possible?

A) Free movement of particles
B) Vibration of particles
C) Strong bonds
D) No motion

✅ Answer: A) Free movement of particles

Q43. Why does a room heater warm up the entire room?

A) Conduction only
B) Convection currents
C) Reflection of heat
D) None

✅ Answer: B) Convection currents

Q44. In convection, heat is transferred by:

A) Vibrations of molecules
B) Movement of molecules from hot to cold
C) Light rays
D) Sound waves

✅ Answer: B) Movement of molecules from hot to cold

Q45. In land breeze, air moves:

A) From sea to land
B) From land to sea
C) From clouds to land
D) None

✅ Answer: B) From land to sea

Q46. In a cooking pot with water, why does water at the top also get hot?

A) Conduction
B) Convection currents in water
C) Radiation
D) Reflection

✅ Answer: B) Convection currents in water

Q47. Which is a natural convection process?

A) Heating iron rod
B) Blowing air with fan
C) Sea breeze
D) Microwave heating

✅ Answer: C) Sea breeze

Q48. Which of these best demonstrates convection?

A) Smoke rising from a chimney
B) Spoon becoming hot
C) Heat from Sun
D) Iron rod heated

✅ Answer: A) Smoke rising from a chimney

Q49. Which factor affects convection in liquids?

A) Density difference
B) Light intensity
C) Shape of container
D) Colour of liquid

✅ Answer: A) Density difference

Q50. Which statement is correct?

A) Convection cannot occur in gases
B) Hot air is denser than cold air
C) Convection causes winds and currents
D) Convection occurs in solids

✅ Answer: C) Convection causes winds and currents

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