My Pals are Here!
Science
© 2008
Marshall
Cavendish (Singapore) Private Limited
© 2009
Marshall
Cavendish
International
Questions to think about…
What are electrical
conductors and
insulators?
Are good conductors
of electricity also
good conductors of
heat?
How do we use
electricity safely?
© 2009 Marshall Cavendish International (Singapore) Private Limited
What is electricity?
• Electricity is conducted through some things better
than others do.
• Some materials are very resistant. Their atoms
hold their electrons very tightly so they cannot move
very well. These things are called insulators. (Can
you give some examples?)
• E.g. rubber, plastic, cloth, glass, dry air etc.
• Some materials have loosely held electrons which
move through them very easily. These are called
• Conductors e.g. most metals like copper,
aluminium, steel etc.
Conductors and insulators
• Take a close look at this wire.
• There is metal on the inside and plastic on
the outside.
• Why?
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Conductors and insulators
• Some materials, like copper, allow an
electric current to flow through them.
• Such materials are called conductors of
electricity.
• Many other metals also conduct electricity
well.
• Hence, wires are usually made of metals.
© 2009 Marshall Cavendish International (Singapore) Private Limited
Conductors and insulators
• Examples of metals that are conductors of
electricity:
o
aluminium
© 2009 Marshall Cavendish International (Singapore) Private Limited
Conductors and insulators
• Examples of metals that are conductors of
electricity:
o
iron
© 2009 Marshall Cavendish International (Singapore) Private Limited
Conductors and insulators
• Examples of metals that are conductors of
electricity:
o
copper
© 2009 Marshall Cavendish International (Singapore) Private Limited
Conductors and insulators
• Examples of metals that are conductors of
electricity:
o
gold
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Conductors and insulators
• Examples of metals that are conductors of
electricity:
o
silver
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Conductors and insulators
• To prevent the electric current from flowing
out of a circuit, wires are coated with plastic.
• Plastic does not allow an electric current to
flow through it.
plastic
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Conductors and insulators
• Other than plastic, many other materials
do not allow an electric current to flow
through them.
• These materials are called nonconductors of electricity.
• Non-conductors of electricity are also
called insulators.
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Conductors and insulators
• Examples of non-conductors of
electricity:
o
paper
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Conductors and insulators
• Examples of non-conductors of
electricity:
o
rubber
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Conductors and insulators
• Examples of non-conductors of
electricity:
o
wood
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Conductors and insulators
• Examples of non-conductors of
electricity:
o
glass
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Conductors and insulators
• Examples of non-conductors of
electricity:
o
clay
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Using electricity safely
• Electricity is useful but it can harm us if we
do not use it carefully.
• Other than getting a nasty shock, we can
cause a fire if we do not use electricity
carefully.
So what can we do to
protect ourselves?
© 2009 Marshall Cavendish International (Singapore) Private Limited
Using electricity safely
• Never try to repair any
electrical equipment or
electrical socket yourself.
• Get an adult or an
electrician who knows
how to repair it.
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Using electricity safely
• When repairing any
electrical equipment, proper
tools with plastic or wooden
handles should be used.
• Such materials are nonconductors of electricity.
• They prevent electricity
from flowing from the
equipment to our hands.
© 2009 Marshall Cavendish International (Singapore) Private Limited
Using electricity safely
• Ensure that there are no
exposed wires in
electrical equipment.
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Using electricity safely
• Never touch
switches or
electrical equipment
with wet hands.
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Using electricity safely
• Do not put too
many plugs into
one socket.
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Using electricity safely
• Use safety devices such as circuit breakers and
fuses.
• Sometimes, fires are accidentally caused when
too much current flows through a circuit.
• Circuit breakers and fuses break a circuit when
too much current flows through them.
circuit breaker
fuse
© 2009 Marshall Cavendish International (Singapore) Private Limited
My Pals are Here!
Science
© 2008
Marshall
Cavendish (Singapore) Private Limited
© 2009
Marshall
Cavendish
International