Chapter Transmission of heat energy. Subject: Physics. Grade 6

1. TRANSMISSION OF HEAT
ENERGY
BY SALAR ALI
A STUDENT OF CLASS 6B

2. HEAT
• Heat is a form of energy that
is transferred from a region
of higher temperature to one
of lower temperature.

3. HEAT TRANSFER METHODS
• 1. CONDUCTION
• 2. CONVECTION
• 3. RADIATION

4. 1. CONDUCTION
• Conduction is the transfer of
heat through a material from the
hot to the cold regions without
any visible movement or flow of
the material.

5. HEAT CONDUCTORS AND INSULATORS
• Heat insulators are not very
good conductors of heat.
• They conduct heat slowly.
• At the other end, heat
conductors conduct heat
faster and they are good
conductors of heat.
CONDUCTORS INSULATORS
Silver Vacuum
Copper Air
Aluminium Cork
Iron Glass

6. 2. CONVECTION
• Convection is the transfer of
heat from one part of a fluid
to another by the movement of
the fluid itself.
• A fluid is a substance which
can flow.
• Liquids and gases are
fluids.

7. Convection continued
• Consider this - when you look at the road in the
summertime on a hot day, you may notice that the air above
the road looks “blurry” – this is convection taking place as
the hot air directly over the road absorbs the heat from the
road and rises. Although the explanation can be quite
complex, convection can help explain why mirages are seen
in the desert.

8. 3. RADIATION
• Radiation transfers heat in the form of electromagnetic
waves which do not need a medium.
• To reduce the loss or gain of heat by radiation, an object
should have a shiny, silvery and smooth surface.
• To increase the loss or gain of heat by radiation, an object
should have a dull, black and rough surface.

9. RADIATION
• Question: If conduction deals
with solids and convection deals
with liquids, how does heat
arrive to Earth from the Sun?
• There is very little matter in
between the Earth and Sun.

10. Radiation continued
• Heat can travel in waves without a
medium (a liquid, solid, or gas).
• Radiation is the term that describes heat
movement without a medium of matter.

11. THE VACUUM FLASK
• A vacuum flask keeps things close to
their original temperature by
reducing the transfer of heat
between the flask and its
surroundings.
• Heat transfer by conduction,
convection and radiation is reduced
by the special features of the flask!