Home PHYSICS TOPIC 6: TRANSFER OF THERMAL ENERGY | PHYSICS FORM 3

# TOPIC 6: TRANSFER OF THERMAL ENERGY | PHYSICS FORM 3

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### TOPIC 6: TRANSFER OF THERMAL ENERGY | PHYSICS FORM 3

##### Conduction
The Concept of Conduction of Heat
Explain the concept of conduction of Heat
##### Conduction is the transfer of heat energy through solids, for example, metals. Generally solid substances contain particles which are close together. Each particle vibrates at one position but cannot move to another position.
Solid materials differ greatly in their ability to conduct HEAT.
Good and Bad Conductors of Heat
Identify good and bad Conductors of Heat
Solid materials differ greatly in their ability to conduct HEAT.
Good conductors
These are the substances which allows the passage of heat energy easily example all metals.
Metals
contain tiny particles called electrons (particles that carry
electricity through metals) which are free to move inside the metal and
carry energy from hotter places to colder places.
These are materials which does not allow the passage of heat and electricity e.g Non – metals, woods.
 GOOD CONDUCTOR BAD CONDUCTOR Silver Aluminum Brass Iron Copper Steel Glass Wood Asbestos Water Air
How to Minimize Heat Losses due to Conduction
Explain how to minimise Heat losses due to Conduction
There are some simple ways to reduce heat loss, including fitting carpets, curtains and draught excluders.
Heat
loss through windows can be reduced using double glazing. The gap
between the two panes of glass is filled with air. Heat loss through
conduction is reduced, as air is a poor conductor of heat. Heat transfer
by convection currents is also reduced by making the gap is very
narrow.
Heat
loss through walls can be reduced using cavity wall insulation. This
involves blowing insulating an material into the gap between the brick
and the inside wall, which reduces the heat loss by conduction. The
material also prevents air circulating inside the cavity, therefore
reducing heat loss by convection.
Knowledge of Conduction in Daily Life
Apply knowledge of conduction in daily life
The difference in conductivity of various materials can be demonstrated using Edser’s apparatus
The apparatus consists of copper can with identical rods of aluminum, copper, lead and iron fixed to the bottom of the can.
The
can is supported by a metal ring which is clamped to a retort stand.
When hot water is poured inside the copper can, heat will be passed
along the rods by conduction.
After
some time, it will be observed that wax coatedon the rods will melt and
move down the rods. Note how far along the rods the wax has melted when
the apparatus reaches a steady state.
This
indicates that the materials from which the rods are made have
different thermal conductivities. Of the four metal rods, the copper rod
is observed to conduct heat more quickly than the rest.
Conduction of Heat Energy through Liquids
• All liquids expect mercury and gases are poor conductors of heat.
• Gases are far worse conductors of heat than liquids.
• Fluids are bad conductors of heat. They transfer heat by means of convection.
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