UK mains Electrical safety
The average UK plug supplies 230V Plastic insulation
at 50Hz of alternating current o prevents people from getting an electric shock.
UK plugs o Wires have 2 layers of insulation (inner and
outer) made of PVC because it is flexible and
doesn’t conduct electricity so is safe to touch
Double insulation
o Any appliance with a plastic casing can’t become
live so don’t need an earth wire
o Some appliances have metal casing but have
insulator sprayed on the inside
Damaged insulation
o can lead to bare wires and lead to electric shocks
Overloading cables
o Results in lots of current flowing through the
Safety features
wires and they can overheat, melt and possibly
The earth pin is longer than the start a fire
other 2 so the appliance is earthed Damp conditions
before current starts to flow so if o are dangerous because water is ionising and can
there’s a short circuit the appliances conduct electricity and cause a short circuit
will immediately shut off so there is The earth wire
no risk of electrocution o carries no current and is for safety purposes only
Cable grip prevents wires from o it prevents the casing from becoming live by
coming out providing a low resistance path to earth creating
a short circuit and causing the current to become
Forces extremely high so the fuse melts and circuit stops
RCCB
Kinetic energy depends on mass and o a residual current circuit breaker
velocity o if the current through the circuit is too high an
electromagnetic switch will break the circuit
Fuses
o always connected to the live wire
o added to a circuit to limit the amount of current
flowing through a circuit
o if the current is too high the fuse will melt and
break the circuit
Speed = distance ÷ time o most common fuses 3A and 13A
Stationary object or travelling at a
Fuse RCCB
constant velocity = no resultant
Very cheap More expensive
force (all acting forces are equal and
Needs to be replaced Can just be switched
opposite) Take a second to melt Switches off immediately with
Gravitational potential energy no delay
depends on the mass of the object
and how high you lift it
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