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The 13 Amp PLUG
Fuse
Earth
Neutral
Cable grip
Flexible
Copper
conductors
Insulating
Casing
Live Wire
FUSES
IN
ACTION
fault
Extra current
melts the 5 Amp
fuse wire
cutting off the
live supply
Fuses are the weakest link in a circuit, preventing fires.
They consist of a short, thin piece of wire with a
low melting point.
EARTH
&
FUSE
Appliances with metal cases need to be earthed.
The earth pin is connected to the case via the
yellow/green wire. If a fault occurs a large current
flows to earth and overloads the fuse.
The earth wire and fuse
L
N
The earth wire and fuse
- -
- -
-
L
FaultLoose wire
N
The earth wire and fuse
- -
- -
-
L
FaultLoose wire
N
The earth wire and fuse
L
E
N
The earth pin is connected to the metal case via the yellow /green earth wire
If a fault develops a larger current can flow down the earth wire
and melt the fuse wire cutting off the supply on the LIVE wire
Errors in Wiring Plugs
1
2
3
Errors in Wiring Plugs
1
2
3
Errors in Wiring Plugs
1
2
3
Errors in Wiring Plugs
1
1. Bare wires showing
2. Proper fuse not installed
3. Earth wire not connected
2
3
Errors in Wiring Plugs
1
1. Bare wires showing
2. Proper fuse not installed
3. Earth wire not connected
2
3
4
5
Errors in Wiring Plugs
1
1. Bare wires showing
2. Proper fuse not installed
3. Earth wire not connected
4. Live and neutral swapped
2
3
4
5
Errors in Wiring Plugs
1
1. Bare wires showing
2. Proper fuse not installed
3. Earth wire not connected
4. Live and neutral swapped
5. Loose cable grip
2
3
4
5
A ring main circuit
Why are sockets wired
in parallel with
each other ?
The longest pin of a plug
is designed to make contact
with the earth wire
FUSES, EARTH WIRE AND PLUGS
Shock
Current
( mA)
Effect
> 25
DEATH
10 - 25
PAIN Can’t let go
0-10
TINGLE
If your body has a resistance
of 100  and you touch a
live wire at 230V, what
happens?
Wet hands have a
much lower resistance.
Safety with mains electricity
*
*
*
*
Replace broken plugs and frayed cables
Keep plugs & cables away from water or heat
Never overload a plug or socket
Don’t use wet hands when switching on or off
Appliances with plastic cases do not need an earth wire
Why not?
The insulating plastic prevents users getting into contact
with ‘Live’ components
CIRCUIT BREAKER
Circuit breakers
work quicker
than fuses.
( saves lives)
CIRCUIT BREAKER
They are
easily reset
by pressing
a button
neutral
melts
live
parallel
earth
series
Brass – stiff, good conductor
Copper – malleable, good conductor
rubber – flexible, good insulator
Stiff plastic – tough, rigid, good insulator
1a. A Fuse cuts off the supply if there is excessive current caused by a fault.
1a. A fuse is on the live side so that the appliance remains safe from the live voltage.
1a Circuit breakers work quicker than fuses.( saves lives)
New switch
location
yes
The off switch should prevent
the live voltage reaching the element
melts