Page 37 - Science Class 07
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waves that exist in the atmosphere. One of the Conductors
most important examples of radia on heat Conductors are the materials or substances
transfer is the heat of the sun coming on the which allow electricity to flow through them.
earth. They are able to conduct electricity because
they allow electrons to flow inside them very
easily. Conductors have this property of
Aim : To show heat gets transferred in
allowing the transi on of heat or light from one
metals.
source to another.
Materials required : A metal rod, wax, nails,
candle. Metals, humans, earth and animal bodies are
all conductors. This is the reason we get electric
Method : Take the metal rod and fix nails on shocks! The main reason is that being a good
it keeping a gap of 4 cm between two nails conductor, our human body allows a resistance-
with the help of the mel ng wax from the
free path for the current to flow from wire to
lighted candle. Now, keep one end of the rod
just about the flame of the candle. A er a our body.
few minutes you will observe that the nails Conductors have free electrons on its surface
begin to fall from the flame. Why does it which allows current to pass through it. This is
happen? the reason why conductors are able to conduct
Actually, due to conduc on, heat gets electricity.
transferred that melts the wax and the nails Examples of Conductors
begin to fall. This ac vity shows that heat v Silver is the best conductor of electricity.
gets transferred in metals.
However, it is costly and so, we don’t use
silver in industries and transmission of
electricity.
v Copper, Brass, Steel, Gold and Aluminium
In a refrigerator, convec on is used to are good conductors of electricity. We use
circulate cold air around the food. Air is them mostly in electric circuits and systems
cooled by the freezer compartment at the in the form of wires.
top of the refrigerator. As it sinks, it is v Mercury is an excellent liquid conductor
replaced by warm air rising from below. The that is used in many instruments.
circula ng air carries heat energy away from
all the food in the fridge. v Gases are not good conductors of electricity
as the par cles of ma er are quite far away
CONDUCTORS AND INSULATORS and thus, they are unable to conduct
You studied about different processes through electrons.
which heat is transferred. But, the transfer of Insulators
heat also depends upon the nature of different
Insulators are the materials or substances which
material through which heat is transferred.
resist or don’t allow the current to flow through
On this basis, we can classify materials into the
them. They are mostly solid in nature and are
following groups:
being used in a variety of systems. They do not
v Conductors v Insulators
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