Electricity in the home
18/2/25
a.c. d.c.
• There are 2 types of electricity supplies:
1) Direct current (d.c.)
2) Alternating current (a.c.)
d.c. a.c.
• The movement of • The movement of charge
charge is only in one changes direction.
direction. • Examples: The UK mains
• Examples: Cells and supply (the electricity in
batteries your homes) is an a.c.
supply at 230 V and a
frequency of 50 Hz.
Cables
Label the 3
This is not a
wires with a
wire but is part
colour and the
of a plug.
type of wire
you think it is.
The 3 colours are: Brown, blue and green & yellow
The 3 types of wire are: Neutral, live and earth
Cables
Neutral
Wire
Cables
Earth
Wire
Neutral
Wire
Cables
Earth
Wire
Neutral
Wire
Live
Wire
Cables
Earth
Wire
Fuse
Neutral
Wire
Live
Wire
BRown: Bottom Right BLue: Bottom Left
Cables
• Live wire: The live wire carries the potential
difference. It alternates between high +ve and –ve
voltage of about 230 V.
• Neutral wire: The neutral wire completes the
circuit – electricity flows in through the live wire
and out through the neutral wire. The neutral wire
is always at 0 V.
• Earth wire: The earth wire is for safety and
protecting the wiring. It carries the current away if
something goes wrong and stops the appliance
casing becoming live. It’s also at 0 V.
• What is the p.d. between the live wire and the
neutral wire?
230 V (for a mains connected appliance)
• What is the p.d. between the live wire and the
earth wire?
230 V (for a mains connected appliance)
• What is the p.d. between the neutral wire and
the earth wire?
0V
Dangers
• Touching the live wire gives you an electric
shock.
• Your body is at 0 V, so if you touch the live
wire, a large p.d. is produced across your body
and current flows through you and causes a
large electric shock.
• Any connection between live and earth, a
current would flow through you, even if a plug
socket is turned off. A current isn’t flowing but
there is still a p.d. in the live wire.
Fuses & Earthing
• Surges in current can occur because of faults in
electrical appliances.
• They can cause melting, fires or deadly shocks.
• The earth wire and fuse are included in appliances
to prevent this.
• The surge in current melts the fuse when the
amount of current is greater than the fuse rating.
• Fuses are connected to the live wire so that
breaking the fuse breaks the circuit.
Household fuses
• As well as fuses in plugs, there are also
household fuses.
• These work in the same way, but protect the
wiring in the house, not just an appliance.
Circuit breakers
• Circuit breakers can be used instead of household
fuses.
• Instead of melting a fuse, a large current may instead
‘trip’ a circuit breaker.
• They turn off quicker than melting fuses.
• So they can be reset, which is much easier than
replacing a fuse.
• But they are more expensive than fuses.
• All appliances with metal cases are usually earthed
to reduce danger of electric shock.
• If the appliance has a plastic casing and no metal
parts showing, then it is said to be double insulated.
• Anything with double insulation doesn’t actually
need an earth wire.
• Cables that only carry live and neutral wires are
called two-core cables.
