9 Electrical Safety v1 0

7/28/2019 9 Electrical Safety v1 0

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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.



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.



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.



What does each wire do?



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).



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.



Materials and properties of plug parts



neutralterminal

earthterminal

cablegrip

fuse

cable

What are the parts of a plug?

liveterminal



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



Can you wire a plug?



Identifying wrongly-wired plugs



Electrical plugs true or false?



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.



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.



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.



How does earthing work?

Wh d l l h i ?



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)
http://www.photos.com/en/search/close-up?oid=4066780&hoid=eba54c06fe318f5e949bf0f45dfb7186


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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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M lti l h i i


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Multiple-choice quiz

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9 Electrical Safety v1 0