Convection

Q.

A sphere, a cube and a thin circular plate have the same mass and are made of the same material. All of them are heated to the same temperature. The rate of cooling is

1. the maximum for the plate and minimum for the sphere

2. the maximum for the sphere and minimum for the plate

3. the maximum for the sphere and minimum for the cube

4. the same for all the three.

Q.

In refrigerator, why are the freezer always locate at the top

Q.

Air has weight.

1. True

2. False

Q.

What is the mode of heat transfer on the top of the fire and on the sides of the fire?

Q.

Why convection is not possible in solids?

Q.

Question 6
Look at the figure. Mark where the heat is being transferred by conduction, by convection and by radiation.

Q.

Give any two applications of thermal convection.

Q.

How is sea breeze caused?

1. Through convection currents

2. Through rains

3. Through conduction

4. Through cyclones

Q. The mode of heat transfer in fluids is convection.

1. True
2. False

Q.

Question 3 (e)
Fill in the blanks :
(e) A cold steel spoon is dipped in a cup of hot milk. It transfers heat to its other end by the process of ___.

Q. If you light a candle and keep one hand above the flame and other on the side, which feels hotter? Which mode of heat transfer takes place? [3 MARKS]

Q. When heat is transferred by actual movement of particles, it is referred to as heat transfer by ___________.

1. conduction
2. convection
3. radiation
4. conduction and radiation

Q.

Convection is the mode of heat transfer that is taking place in boiling of a water.

1. True

2. False

Q. In which of the following mediums can convection take place?

1. Iron rod
2. Air
3. Wooden bowl
4. Water

Q.

Which of the following statements is true about convection?

1. Convection takes place in solids

2. Convection takes place in fluids

3. Convection requires a medium for transmission.

4. Convection does not require a medium for transmission

Q. What is conduction? How does it occur?

Q.

A hot air balloon rises up, because its density is more than air.

1. True
2. False

Q.

Give a method of heat transfer in gases.

Q.

In convection, heat is transferred?

Q.

Heat travels through a vacuum by

1. radiation

2. convection

3. conduction

4. Both (A) and (B)

Q.

A laboratory thermometer $A$ is kept $7cm$ away on the side of the flame while a similar thermometer $B$ is kept $7cm$ above the flame of a candle. Which of the thermometers $A$ or $B$ will show a greater rise in temperature? Give a reason for your answer.

Q. Water is being boiled in a steel container kept on a heat source. What is the primary mode of heat transfer used for water in this case?

1. Convection

2. Radiation

3. Polarization

4. Conduction

Q.

Liquids and gases are generally _________________ conductors of heat.

Q. Which of the following statement(s) is/ are true about convection?
1. Convection requires a medium for transfer of heat.
2. In liquids, the predominant mode of heat transfer is convection.
3. In convection, heat flows from the cold end to the hot end of the substance.

1. 1 and 3 only
2. 2 and 3 only
3. 1 and 2 only
4. 1, 2 and 3

Q.

Which process is responsible for land and sea breeze? Explain the process and how it is different from radiation? [5 MARKS]

Q.

Name the general mode of heat transfer in [2 MARKS]
a) Solids
b) Liquids and gases.

Q.

Does convection need a medium ?

Q.

Which mode of heat transfer takes place when the lower part of the pan gets heated up when kept on the burning stove

Q. Land breeze and Sea breeze are examples of heat transfer by:

1. Conduction
2. Convection
3. Radiation
4. All of them

Q.

Heat transfer happens by the movement of molecules from one place to another in the case of _______ of heat.