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Class 9 Physics Chapter 9


Updated: 29 Oct 2023

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Class 9 Physics Chapter 9 is about “Transfer of Heat“. This article includes topics such as Transfer of Heat, Conduction of Heat, Mechanism of Heat Conduction, Good and Bad Thermal Conductors, Practical Applications of Conduction of Heat (Cooking pots and pans, Plastic Foam, Wire Gauze, Pot holders and Table mats, Woolen Clothes, Igloos, Ice Box, Soldering), Thermal Conductivity, Convection of Heat, Mechanism of Heat Convection, Practical Applications of Heat Convection (Heating Water, Sea Breeze, Riding on Thermals, Refrigerator, Ventilation), Radiation of Heat, Mechanism of Radiation of Heat, Good and Bad Emitters and Absorbers, Practical Application of Radiation of Heat (Colouring Materials, Texture of the Surface, Satellite Protective Coating, Thermos Flask), Green House Effect and Global Warming, Mechanism of Green House Effect, Importance of Green House Effect.

Table of Content
  1. Class 9 Physics Chapter 9 Notes
    1. Transfer of Heat Notes
    2. Class 9 Physics Chapter 9 SLO Notes
  2. Class 9 Physics Chapter 9 MCQs
    1. Transfer of Heat
    2. Conduction of Heat
    3. Mechanism of Heat Conduction
    4. Good and Bad Thermal Conductors
    5. Practical Applications of Conduction of Heat
      1. Cooking pots and pans
      2. Plastic Foam
      3. Wire Gauze
      4. Pot holders and Table mats
      5. Woolen Clothes
      6. Igloos
      7. Ice Box
      8. Soldering
    6. Thermal Conductivity
    7. Convection of Heat
    8. Mechanism of Heat Convection
    9. Practical Applications of Heat Convection
      1. Heating Water
      2. Sea Breeze
      3. Riding on Thermals
      4. Refrigerator
      5. Ventilation
    10. Radiation of Heat
    11. Mechanism of Radiation of Heat
    12. Good and Bad Emitters and Absorbers
    13. Practical Application of Radiation of Heat
      1. Colouring Materials
      2. Texture of the Surface
      3. Satellite Protective Coating
      4. Thermos Flask
    14. Green House
      1. Mechanism of Green House Effect
      2. Importance of Green House Effect
  3. Physics Class 9 MCQs (All Chapters)

Class 9 Physics Chapter 9 Notes

Transfer of Heat Notes

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Class 9 Physics Chapter 9 Notes

Download Chapter 9 Notes

Class 9 Physics Chapter 9 SLO Notes

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Class 9 Physics Chapter 9 SLO Notes

Download Chapter 9 SLO Notes

Class 9 Physics Chapter 9 MCQs

Transfer of Heat

1 How many primary ways are there for heat transfer?
(a) One
(b) Two
(c) Three
(d) Four
Show Answer

Three


2 Which of the following is NOT a form of heat transfer?
(a) Conduction
(b) Convection
(c) Radiation
(d) Reflection
Show Answer

Reflection

To Download Complete Notes of Physics Notes 9 Class, Click on the given link.

Conduction of Heat

3 What is the term for the flow of thermal energy through matter from higher temperature to lower temperature without matter movement?
(a) Radiation
(b) Convection
(c) Insulation
(d) Conduction
Show Answer

Conduction


4 What is the process by which heat energy is transferred from particle to particle within a material?
(a) Convection
(b) Radiation
(c) Conduction
(d) Insulation
Show Answer

Conduction

Mechanism of Heat Conduction

5 How is heat transferred through conduction in a solid material like an iron rod?
(a) By the movement of the material as a whole
(b) Through the rapid movement of free electrons
(c) By emitting electromagnetic waves
(d) By convection currents
Show Answer

Through the rapid movement of free electrons


6 What happens to the atoms in the hotter part of the iron rod in the conduction process?
(a) They remain stationary
(b) They vibrate with less energy
(c) They vibrate more violently
(d) They emit light
Show Answer

They vibrate more violently


7 What are free electrons in a metal responsible for?
(a) Blocking heat transfer
(b) Emitting radiation
(c) Transferring energy through collisions
(d) Generating convection currents
Show Answer

Transferring energy through collisions


8 How is heat energy transferred from particle to particle in conduction?
(a) Through the emission of light
(b) By the movement of the material as a whole
(c) Through collisions between particles
(d) By electromagnetic waves
Show Answer

Through collisions between particles


9 What is the term for the electron that can move freely throughout the atom?
(a) Bound electron
(b) Proton
(c) Free electron
(d) All of these
Show Answer

Free electron

Good and Bad Thermal Conductors

10 Which term describes materials that allow heat to pass through them easily?
(a) Heat insulators
(b) Good conductors
(c) Bad conductors
(d) Insulating conductors
Show Answer

Good conductors


11 Which term is used for materials that do not allow heat to pass through them easily?
(a) Heat insulators
(b) Good conductors
(c) Thermal transmitters
(d) Conductive insulators
Show Answer

Heat insulators


12 Why are good conductors of heat often used in cooking utensils?
(a) To make food taste better
(b) To reduce the weight of the utensils
(c) To evenly distribute heat and cook food more quickly
(d) To make the utensils more colorful
Show Answer

To evenly distribute heat and cook food more quickly


13 Which of the following materials is a good conductor of heat?
(a) Wood
(b) Rubber
(c) Copper
(d) Plastic
Show Answer

Copper


14 Among solids, liquids, and gases, which state of matter typically conducts heat the best?
(a) Solids
(b) Liquids
(c) Gases
(d) All conduct heat equally well
Show Answer

Solids


15 Why are metals generally good conductors of heat?
(a) They have closely connected atoms
(b) They contain trapped air
(c) They have large inter-molecular distances
(d) They lack free electrons
Show Answer

They have closely connected atoms


16 Why is water a poor conductor of heat?
(a) It contains free electrons
(b) It has closely packed molecules
(c) It has small inter-molecular distances
(d) It has relatively large inter-molecular distances
Show Answer

It has relatively large inter-molecular distances


17 What is the thermal conductive ability of air compared to water?
(a) Air conducts heat better than water
(b) Air and water have similar thermal conductive abilities
(c) Water conducts heat better than air
(d) Air does not conduct heat at all
Show Answer

Water conducts heat better than air

Practical Applications of Conduction of Heat

Cooking pots and pans

18 Why are cooking pots and pans typically made of metals, which are good thermal conductors?
(a) To make them heavy
(b) To conduct heat to the food and spread it evenly
(c) To make them more durable
(d) To insulate the food from heat
Show Answer

To conduct heat to the food and spread it evenly

Plastic Foam

19 Why are plastic foam and fiberglass used in the walls and ceilings of homes?
(a) To make the walls and ceilings heavier
(b) To conduct heat effectively
(c) To keep homes cool in summer and warm in winter
(d) To reduce the insulation properties of the home
Show Answer

To keep homes cool in summer and warm in winter

Wire Gauze

20 What is the purpose of placing wire gauze over a flame when heating a glass beaker?
(a) To conduct heat into the glass beaker
(b) To protect the glass beaker from concentrated heat
(c) To insulate the flame
(d) To increase the temperature of the flame
Show Answer

To protect the glass beaker from concentrated heat

Pot holders and Table mats

21 Why are pot holders and table mats for hot pans made of poor conductors like cloth and wood?
(a) To make them heavier
(b) To conduct heat to the hands
(c) To avoid burning of hands
(d) To make them more durable
Show Answer

To avoid burning of hands

Woolen Clothes

22 How do woolen clothes help in keeping the body warm in winter?
(a) By conducting heat away from the body
(b) By trapping heat and preventing its flow out
(c) By making the body sweat more
(d) By increasing body heat production
Show Answer

By trapping heat and preventing its flow out

Igloos

23 What property of ice and snow in igloos helps minimize the loss of heat from the inside due to conduction?
(a) They conduct heat efficiently
(b) They trap heat
(c) They act as thermal insulation
(d) They melt easily
Show Answer

They act as thermal insulation

Ice Box

24 How does an ice box keep ice from melting?
(a) By conducting heat into the box
(b) By preventing the flow of outside heat into the box
(c) By increasing the temperature inside the box
(d) By using metal walls
Show Answer

By preventing the flow of outside heat into the box

Soldering

25 In which process, heat transferred by conduction when objects are in direct contact?
(a) Cooking
(b) Radiation
(c) Convection
(d) Soldering
Show Answer

Soldering

Thermal Conductivity

26 What does the thermal conductivity of a substance measure?
(a) Heat conduction
(b) Temperature
(c) Material properties
(d) Length
Show Answer

Heat conduction


27 What factors affect the rate of heat flow through a medium?
(a) Length, area, material
(b) Color, texture, size
(c) Pressure, volume, density
(d) Temperature, color, size
Show Answer

Length, area, material


28 Which substance has the highest thermal conductivity?
(a) Silver
(b) Copper
(c) Gold
(d) Aluminum
Show Answer

Silver


29 Which of the following materials has the lowest thermal conductivity?
(a) Silver
(b) Copper
(c) Steel
(d) Lead
Show Answer

Lead


30 How the length of a rod affects the rate of heat flow:
(a) Longer length results in faster heat flow
(b) Longer length results in slower heat flow
(c) Length has no effect on heat flow
(d) None of these
Show Answer

Longer length results in slower heat flow


31 How does the cross-sectional area of a rod affect the rate of heat flow?
(a) Larger cross-sectional area allows for faster heat flow
(b) Smaller cross-sectional area allows for faster heat flow
(c) Cross-sectional area has no effect on heat flow
(d) None of these
Show Answer

Larger cross-sectional area allows for faster heat flow


32 How does the difference of temperature between two faces of a slab affect the rate of heat flow?
(a) Increases the rate of heat flow
(b) Decreases the rate of heat flow
(c) Has no effect on the rate of heat flow
(d) None of these
Show Answer

Increases the rate of heat flow


33 What is the symbol used to represent thermal conductivity?
(a) T
(b) H
(c) k
(d) C
Show Answer

k


34 What is the SI unit for thermal conductivity?
(a) Kelvin (K)
(b) Watts per meter per kelvin (W/m.K)
(c) Joules per second (J/s)
(d) Celsius per meter ({}^oC/m)
Show Answer

Watts per meter per kelvin (W/m.K)

Convection of Heat

35 What is the term for the transfer of heat from one place to another by the bulk motion of fluids?
(a) Conduction
(b) Radiation
(c) Convection
(d) Insulation
Show Answer

Convection


36 What is convection of heat primarily associated with?
(a) Solids
(b) Liquids
(c) Gases
(d) Fluids
Show Answer

Fluids


37 In which state of matter does convection occur most prominently?
(a) Solids
(b) Liquids
(c) Gases
(d) Plasma
Show Answer

Gases

Mechanism of Heat Convection

38 How is heat transferred in convection?
(a) Through electromagnetic radiation
(b) By direct contact between particles
(c) Through the bulk movement of fluids
(d) Via conduction through solid particles
Show Answer

Through the bulk movement of fluids


39 What happens to the particles in a fluid when it is heated, causing convection?
(a) They remain stationary
(b) They vibrate in place
(c) They become more tightly packed
(d) They become less dense and rise
Show Answer

They become less dense and rise


40 What is the term for the circulation of fluid due to temperature differences, causing warmer fluid to rise and cooler fluid to sink?
(a) Conduction
(b) Radiation
(c) Convection current
(d) Insulation
Show Answer

Convection current

Practical Applications of Heat Convection

Heating Water

41 What establishes a continuous circulatory flow in convection within the water?
(a) Expansion of cold wate
(b) Expansion of warm water
(c) Conduction
(d) Radiation
Show Answer

Expansion of warm water


42 What causes the heated portion of water at the bottom to move upward?
(a) It becomes more dense
(b) It contracts
(c) It expands and becomes less dense
(d) It remains stationary
Show Answer

It expands and becomes less dense


43 Why is convection important for boiling water in an electric kettle?
(a) It lowers the temperature of water
(b) It causes the water to freeze
(c) It circulates heat, warming the lower layers of water first
(d) It prevents the water from heating up
Show Answer

It circulates heat, warming the lower layers of water first

Sea Breeze

44 What causes coastal breezes during the day near the sea?
(a) Hot air from the land rises, drawing in cold sea air
(b) Cold air from the land rises, drawing in hot sea air
(c) The sea freezes, creating a breeze
(d) There is no breeze near the sea during the day
Show Answer

Hot air from the land rises, drawing in cold sea air

Riding on Thermals

45 How do thermals benefit birds and glider airplanes?
(a) They provide shade
(b) They allow them to fly without flapping their wings
(c) They cause turbulence in the air
(d) They cool the surrounding air
Show Answer

They allow them to fly without flapping their wings

Refrigerator

46 In a refrigerator, how is convection used to keep food cold?
(a) By freezing the air inside the refrigerator
(b) By circulating warm air around the food
(c) By circulating cold air around the food
(d) By blocking all air circulation
Show Answer

By circulating cold air around the food

Ventilation

47 How is convection used in ventilation systems?
(a) By heating the air inside the room
(b) By blocking airflow near the ceiling
(c) By allowing warm air to escape while drawing in fresh air
(d) By creating a vacuum inside the room
Show Answer

By allowing warm air to escape while drawing in fresh air

Radiation of Heat

48 How is the transfer of heat from a hotter place to a colder place with or without a material medium defined?
(a) Convection of heat
(b) Conduction of heat
(c) Radiation of heat
(d) Advection of heat
Show Answer

Radiation of heat


49 How does heat from an open campfire primarily reach us when sitting beside it?
(a) By conduction
(b) By convection
(c) By radiation
(d) By direct contact with flames
Show Answer

By radiation


50 What is the primary method of heat transfer responsible for warming the Earth from the Sun?
(a) Conduction
(b) Convection
(c) Radiation
(d) Insulation
Show Answer

Radiation


51 Why doesn’t conduction or convection play a significant role in the transfer of heat from the Sun to the Earth?
(a) The Sun is not hot enough to emit heat
(b) There’s no material medium for conduction or convection in the vacuum of space
(c) Conduction and convection are more efficient on Earth
(d) None of these
Show Answer

There’s no material medium for conduction or convection in the vacuum of space


52 What is unique about radiation of heat compared to conduction and convection?
(a) It requires a material medium for transfer
(b) It always occurs at a slower rate
(c) It doesn’t require a material medium for transfer
(d) It only takes place in solids
Show Answer

It doesn’t require a material medium for transfer

Mechanism of Radiation of Heat

53 How heat energy is primarily transferred through radiation?
(a) By conduction of molecules
(b) By convection of particles
(c) By electromagnetic waves
(d) By direct contact between objects
Show Answer

By electromagnetic waves


54 What causes electromagnetic radiation, which is responsible for heat transfer through radiation?
(a) The movement of molecules
(b) The acceleration of electric charges
(c) The rotation of objects
(d) The expansion of materials
Show Answer

The acceleration of electric charges


55 At what temperature does an object stop radiating heat energy through radiation?
(a) 0 degrees Celsius
(b) 0 degrees Fahrenheit
(c) Absolute zero (0 K)
(d) Room temperature
Show Answer

Absolute zero (0 K)


56 What part of the electromagnetic spectrum is typically associated with the radiation of heat, although it is not visible light?
(a) Ultraviolet
(b) X-rays
(c) Infrared
(d) Microwave
Show Answer

Infrared

Good and Bad Emitters and Absorbers

57 Which color is often associated with being a good absorber of radiation?
(a) White
(b) Black
(c) Silver
(d) Red
Show Answer

Black


58 Why does a black car warm up more quickly in the sun than a car of any other color?
(a) Black is a poor absorber of heat
(b) Black is a good reflector of heat
(c) Black is a good absorber of heat
(d) Black is a poor radiator of heat
Show Answer

Black is a good absorber of heat


59 What affects the rate of energy transfer by radiation?
(a) The shape of the object
(b) The size of the object
(c) The color and texture of the surface
(d) The weight of the object
Show Answer

The color and texture of the surface


60 Why are white clothes worn in hot climates?
(a) Good reflector, poor absorber
(b) Good heat absorption
(c) Reflective and high absorptive
(d) Cooler choice
Show Answer

Good reflector, poor absorber

Practical Application of Radiation of Heat

Colouring Materials

61 Why are the cooling fins on the back of a refrigerator often painted black?
(a) To absorb heat more effectively
(b) To reflect heat away
(c) To prevent heat loss
(d) To improve the appearance
Show Answer

To absorb heat more effectively

Texture of the Surface

62 What type of material is often used as a radiant barrier to reduce heat transfer through radiation?
(a) Polished metal
(b) ARMA foil
(c) Black paint
(d) Wood
Show Answer

ARMA foil

Satellite Protective Coating

63 What is the purpose of the highly reflective metal foil covering satellites like the Hubble Space Telescope?
(a) To increase temperature changes
(b) To minimize temperature changes
(c) To absorb more heat
(d) To improve communication
Show Answer

To minimize temperature changes

Thermos Flask

64 How does a thermos flask prevent heat transfer?
(a) By conducting heat away
(b) By allowing convection currents
(c) By minimizing conduction, convection, and radiation
(d) By absorbing heat from the surroundings
Show Answer

By minimizing conduction, convection, and radiation

Green House

65 Warming of the Earth’s surface due to the atmosphere is said to be:
(a) Global cooling
(b) The greenhouse effect
(c) Atmospheric cooling
(d) Solar heating
Show Answer

The greenhouse effect


66 How does the greenhouse effect impact the Earth’s surface temperature?
(a) It decreases the surface temperature
(b) It has no effect on the surface temperature
(c) It warms the surface temperature
(d) None of these
Show Answer

It warms the surface temperature


67 What factors determine the strength of the greenhouse effect?
(a) The color of the atmosphere
(b) The composition of the atmosphere
(c) The distance from the sun
(d) The amount of water vapor in the atmosphere
Show Answer

The composition of the atmosphere


68 Which of the following is a greenhouse gas?
(a) Oxygen
(b) Nitrogen
(c) Carbon dioxide
(d) Hydrogen
Show Answer

Carbon dioxide

Mechanism of Green House Effect

69 How does Earth receive energy from the Sun?
(a) In the form of ultraviolet radiation only
(b) In the form of visible, ultraviolet and near-infrared radiation
(c) In the form of X-rays
(d) In the form of gamma rays
Show Answer

In the form of visible, ultraviolet and near-infrared radiation


70 What percentage of solar energy is reflected to space by the atmosphere and clouds?
(a) 26%
(b) 19%
(c) 45%
(d) 60%
Show Answer

26%


71 What percentage of solar energy is absorbed by the atmosphere and clouds?
(a) 10%
(b) 19%
(c) 26%
(d) 40%
Show Answer

19%


72 How does the atmosphere gain heat in addition to the absorption of solar and thermal radiation?
(a) By conduction
(b) By convection
(c) By latent heat fluxes from the surface
(d) By reflection
Show Answer

By latent heat fluxes from the surface

Importance of Green House Effect

73 Why is the greenhouse effect important for the survival of life on Earth?
(a) It cools the Earth’s surface
(b) It prevents the formation of clouds
(c) It warms the Earth’s surface, making it habitable
(d) It causes extreme temperature fluctuations
Show Answer

It warms the Earth’s surface, making it habitable


74 How much warmer is the Earth’s surface due to the presence of greenhouse gases in the atmosphere?
(a) 10 \ {}^o C warmer
(b) 20 \ {}^o C warmer
(c) 33 \ {}^o C warmer
(d) 50 \ {}^o C warmer
Show Answer

33 \ {}^o C warmer


75 Which greenhouse gas is primarily responsible for the increase in Earth’s temperature due to human activities?
(a) Methane (CH_4)
(b) Carbon dioxide (CO_2)
(c) Ozone (O_3)
(d) Water vapor (H_2O)
Show Answer

Carbon dioxide (CO_2)

Physics Class 9 MCQs (All Chapters)


Jawad Khan

Jawad Khan

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