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DC and AC V
DC stands for "Direct
Current" ­ the current only
flows in one direction:
Time
1/50th s
AC stands for "Alternating 240V
Current" ­ the current
changes direction 50 times
every second (frequency = T
50Hz)
V…read more

Slide 3

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Fuses
Fuses are _______ devices. If
there is a fault in an appliance
which causes the ____ and
neutral (or earth) wire to cross
then a ______ current will flow
through the _____ and cause it
to _____. This will break the
_______ and protect the
appliance and user from further
_____.
Words ­ large, harm, safety, melt, live, circuit, fuse…read more

Slide 4

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Circuit breakers
If the current becomes too high the __________ is
activated. This will ______ the iron and the contact will
be _______. This will break the circuit.
Circuit breakers have two main advantages over fuses:
they work ______ and can easily be ______.
Words ­ electromagnet, broken, attract, reset, quicker…read more

Slide 5

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Earth wires
Earth wires are always used if an appliance has a _____
case. If there is a _____ in the appliance, causing the live
wire to ______ the case, the current "_______" down the
earth wire and the ______ blows.
Words ­ fuse, fault, metal, surges, touch…read more

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Power and fuses
Power is "the rate of doing work".
The amount of power being used in
an electrical circuit is given by: P
Power = voltage x current
in W in V in A V I
Using this equation we can work out the fuse rating for any
appliance. For example, a 3kW (3000W) fire plugged into a
240V supply would need a current of _______ A, so a
_______ amp fuse would be used (fuse values are usually 3,
5 or 13A).…read more

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