Heat is a form of energy that is transferred between objects in three main ways: conduction, convection, and radiation. Conduction requires physical contact between objects and is a slower process of heat transfer. Convection relies on the movement of molecules within fluids like liquids and gases and can transfer heat faster. Radiation can transfer heat across empty space through electromagnetic waves and does not require a medium. Common examples of heat transfer by different modes and their distinguishing features are provided.

1. HEAT ENERGY
BY RIDDHAM DHARIWAL

2. Key
concepts
Units of
temperature
and
measuring it
Effects of
heat
Methods of
heat transfer

3. INTRO
• Did you ever wonder what is this hot and cold?
• •Yes, it is the abundance or absence of heat, If you feel cold, that means there is less heat but when you
feel hot, that means heat is abundant.
• •What is heat?
• •Heat is nothing but the movement of atoms, the more the atoms move, then you feel hotter but the
less the atoms move, you feel colder
• •The S.I unit of heat is joules as it is a form of energy.
• •A calorie is defined as the amount of energy To heat 1 gram of water by 1 degree Celsius

4. TEMPERATURE
• Temperature is defined as the degree of hotness or coldness of a body.
• There are three units of temperature:
Celsius was named after Andrew Celsius
Celsius
• Celsius is also called as centigrade
Fahrenheit was named after Daniel Gabriel Fahrenheit
Fahrenheit
• (℃ × 1.8) + 32
The term ‘Kelvin’ was coined by William Thomson
Kelvin
• It officially stars from the point where atoms do not move
Contd. At slide 5

5. MEASURING TEMPERATURE
• We know that the units of temperature are Celsius, Fahrenheit and Kelvin but how to convert Celsius
into Fahrenheit or Kelvin. Lets see how
• ℃ 𝑖𝑛𝑡𝑜 ℉ 𝑜𝑟 𝑣𝑖𝑐𝑒 𝑣𝑒𝑟𝑠𝑎
℃
5
=
(℉ −32)
9
• ℃ 𝑖𝑛𝑡𝑜 °𝐾 ℃ + 273.15 = °𝐾
• Use of thermometer
• A thermometer could show temperature in all the units of temperature
• It shows Celsius and kelvin by the 100 divisions in it using mercury
• It shows Fahrenheit by it’s 180 divisions in it
• The thing common in thermometers regardless of unit is that they start from the melting point of water
to the boiling point of water

6. EFFECTS OF HEAT
• There are three effects of heat:
• Change in size
• When a body heats, it expands but contracts when cooled.
Eg. The iron in railway tracks expand during the summer and shrink during the winter, this is the reason for
regular maintenance of railway tracks.
• Change in temperature
• Temperature falls on Absence of heat and rises on Abundance of heat
• Change in state
• Temperature can also alter the state of a body
• Eg
•Solid
Melting
•Liquid
Evaporation
•Gas
Condensation
•Liquid
Freezing
•Solid
Changes by
temperature

7. MODES OF TRANSFER OF HEAT
• There are three types of ways that heat could be transferred by:
1. Conduction: it is a process of transferring heat from a hot end to a cold end of an object. A medium is
required for conduction. The objects which are good in conduction are called as conductors whereas
objects which are good in blocking heat are called as insulators.
2. Convection: Convection is the process where heat is transferred by the movement of molecules of the
medium. As a solid has negligible movement of molecules inside it, a solid could not be heated by
convection but liquids and gases can be heated by convection.
3. Radiation: it is the process by which heat could pass from a heat-abundant body to a body which has
less heat without affecting the bodies. This kind of transfer is also possible in vacuum .

8. DIFFERENCE BETWEEN MODES OF HEAT
TRANSFERRING
Conduction
• Medium is necessary for
conduction to happen
• Conduction could not
happen in vacuum
• The particles during
conduction are in position
• Heat could be transferred in
any direction by this mode
• This process is slow
Convection
• No medium is required for
radiation to occur
• Radiation is possible in vacuum
• The medium remains
unaffected
• Heat could be transferred in all
directions but on a straight
path
• Heat Is transferred at speed of
light
Radiation
• Medium is necessary for
Convection
• Convection is not possible
in vacuum
• The particles of the
medium move upwards
along with the heat
• Heat can only be
transferred upward
• This process is faster than
conduction

9. Quiz Time !!!

10. MULTIPLE CHOICE QUESTIONS
Q.1 : Tell the transferring mode of heat in which it cannot go in all directions ?
Option A: Conduction Option B: Convection Option C: Radiation
Q.2 : Find the odd one out
Option A: Air Option B: Aluminum Option C: Graphite
Q.3 : Complete the Correlation Heat:Joules::Temperature:_____
Option A: Calories Option B: IDK:) Option C: Kelvin

11. GIVE AWNSER
• Why are exhaust fans put at a high height ?
Ans: Because of Convection, as the heat moves upwards due to convection, that’s why Exhaust fans are put
at a high height.
• Why do you feel Cool under a tree ?
Ans: Because A tree’s leaves blocks the radiating heat from coming to us but when we are not under a
tree’s shade, The radiating heat falls on us.
• Do you think That radiating heat from space is dangerous ?
Ans: (Answers may vary)