9 electrical safety v1 0
TRANSCRIPT
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How safe is this office?
Can you spot the electrical hazards in this busy office?
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Why is electricity dangerous?
Warning signs are used to alert
people to the presence of high
voltage electricity.
When a current passes through
living material, it causes an
electric shock.
This interferes with nerve signals
from the brain to the body, and
can cause a heart attack, muscle
spasms and breathing difficulties.Other dangers are overheated
and faulty appliances, which may
lead to electrical fires.
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Do not stick anything other than a plug in a socket.
Never mix water and electricity.
Do not overload sockets.
What precautions can be taken to make electricity safer?
How can electricity be used safely?
Wire plugs correctly.
Regularly check cables for
breaks and lose wires.
Use earth wires, fuses and circuit breakers to prevent
accidents, in case faults develop.
Although electricity can be very dangerous, it is also
incredibly useful and is essential for modern life.
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Electrical safety true or false?
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An electrical cable contains
three wires.
copper
insulating plastic
What is inside an electrical cable?
These wires are made ofcopper
because it is a good conductor of
electricity. Each wire is made of
thin strands of copper to keep the
cable flexible.
Each wire is encased in plastic
to stop the wires touching and
causing a short circuit. Plastic isused as it is a good insulator, as
well as being tough and flexible.
The whole cable is encased in
another layer of plastic.
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The three pins in an electrical
plugs are connected to the
three wires inside a cable.
Why do plugs have three pins?
Two of the wires form the
electrical circuit. The third
is a safety feature.
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How does this colour scheme help avoid confusion?
earth
neutral
live
How are wires identified?
A standard colour scheme is used for the plastic casing
to show the function of each type of wire.
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What does each wire do?
The neutral wire completes the
circuit. It is kept at a zero voltage
by the electricity company.
The earth wire is a
safety wire that is needed
to earth appliances witha metal case.
This makes it safer to
touch the appliance if it
develops a fault.
The live wire carries a current
that alternates between a
negative and positive voltage.
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What does each wire do?
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Electrical sockets make
mains electricity available
for use.
NEVER PUT ANYTHING OTHER THAN A PLUG
IN AN ELECTRICAL SOCKET!
Remember, the electricity in a plug socket is at 230V, which
could kill you, if you get a shock.
What is an electrical socket?
They connect the plugs on
appliances to the mains
electricity system, through
the three different types of
wire (live, neutral and earth).
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An electrical plug is inserted
into a socket and the cable that
is attached to the plug carries
electricity to the appliance.
How do plugs and sockets carry current?
A plug has three pins which fit the three
holes on a socket in one way only, so
the plug cannot be wrongly connected.
Plugs and sockets are a safe and
convenient way of using electricity.
The pins are made ofbrass,which is
a good conductor. It is also hard and
so will not bend.
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Materials and properties of plug parts
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neutralterminal
earthterminal
cablegrip
fuse
cable
What are the parts of a plug?
liveterminal
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Make sure that thewires are connected to
the correct terminals:
When wiring a plug, always check the following:
How do you wire a plug?
There are no loose or
bare wires.
The grip should firmlyhold the cable in place.
A fuse of the correct
value is fitted.
blue to neutral
/green to earth
brown to live
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Can you wire a plug?
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Identifying wrongly-wired plugs
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Electrical plugs true or false?
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A fuse is a safety device,
which breaks the circuit,
if the current is too high.
What is a fuse?
This protects the cable from
overheating and catching fire.
All UK plugs are fitted withfuses. Fuses are available
in a range of amperes to
suit different current values.
fuse
Sockets and extensions thatare overloaded with
appliances are especially at
risk of catching fire.
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How do fuses work?
A fuse contains a thin wire, which
melts if the current is too high.
Fuses act as an early warning
system, preventing appliancesfrom being damaged by surges
in electricity and warning
owners of faults.
thinwire
This breaks the circuit and so
electricity is unable to flow
through the appliance.
The appliance stops workingand any danger has been
averted.
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What is earthing?
Earthing is a process used to increase the safety of
electrical appliances.
Cables contains an earth wire to provide an alternative path
for current if appliances develop faults.
An earth wire is essential for an
appliance with a metal case.
When an appliance is working correctly, no electricity
flows through the earth wire.
If the live wire becomes loose
and touches the metal case, a
very large current flows to earth
and blows the fuse, breakingthe circuit.
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How does earthing work?
Wh d l l h i ?
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Why do some plugs only have two pins?
Instead of having a pin for
the earth connection, the
plug has a clip on the side.
This plug and socketsystem is sometimes
referred to as Continental
European.
Some sockets in Europe have two round slots for the pins.
Does this mean that the appliances are not earthed?
This clip corresponds to acontact point in the socket
and connects the
appliance to earth.
Wh t d d bl i l t d ?
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What does double insulated mean?
Double insulatedappliances
have plastic cases, without
any wires connected to the
case.
symbol on double
insulated appliance
This means that the case
cannot become live,
because plastic does not
conduct electricity.
So, if one layer of insulation
is damaged the appliance is
still safe for the user.
Another way of improving the safety of electrical appliances
is to make them double insulated.
E thi d f t f l ?
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Earthing and fuses true or false?
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Gl (1/2)
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Glossary (1/2)
double insulatedAn appliance that contains internalinsulation and a non-conducting case.
earthingA method to improve the safety of appliancesby providing a low resistance path for current to flow to earth.
earth wireA safety wire that connects the metal case of
an appliance to earth. It is covered with a yellow and greeninsulator.
electric shock A danger associated with electricity.When current runs through living matter it can cause heart
attacks, breathing difficulties and muscle spasms.
fuseA safety component containing a length of wire,which heats up and melts (blows) if the current is too high.
Gl (2/2)
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Glossary (2/2)
live wireA wire that carries mains electricity to anappliance. It is covered with a brown insulator.
neutral wireA wire that carries current away from anappliance to complete the circuit. It is covered in a blueinsulator.
plugA device that fits into a socket to connect anappliance to the mains electricity.
socketA connection point for a plug, which makesmains electricity available for use.
A
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Anagrams
M lti l h i i
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Multiple-choice quiz