1. flippedaroundphysics.com 2016
Wiring a plug
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2. flippedaroundphysics.com 2016
Fuse
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3. flippedaroundphysics.com 2016
Objectives
how do fuses work?
what job do they do?
how do you calculate which fuse
to fit?
flippedaroundphysics.com 2016

4. flippedaroundphysics.com 2016
The domestic plug
EARTH WIRE
LIVE WIRE
FUSE
NEUTRAL WIRE
CABLE GRIP
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5. flippedaroundphysics.com 2016
Anatomy of a fuse
non-conducting ceramic/glass body
low melting point fuse wire
symbol
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6. flippedaroundphysics.com 2016
Fuse - normal operation
Fuse – current too high
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7. flippedaroundphysics.com 2016
Normally working appliance
Metal casing
LIVE
fuse
NEUTRAL
EARTH
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8. flippedaroundphysics.com 2016
Appliance with a fault
Metal casing
LIVE
fuse
NEUTRAL
EARTH
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9. flippedaroundphysics.com 2016
Fuses come in different sizes
3A, 5A, 13A
Which would you choose for a washing machine
needing 11.2A to work properly?
Which would you choose for a table lamp
needing 1.6A to work properly?
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10. flippedaroundphysics.com 2016
Choosing the correct fuse
Find out the power rating of the appliance
2) Using current (A) = power/voltage calculate the
current that the appliance needs (remember that mains
voltage is 230V)
3) Choose a fuse that is slightly larger than the
current needed
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11. flippedaroundphysics.com 2016
Example
A stereo system is rated at 800W. What fuse
Should be fitted?
Current = power/voltage
= 800/230
= 3.48A
Therefore a 5A fuse should be fitted
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12. flippedaroundphysics.com 2016
Calculate the current needed by the following
appliances and the fuse needed.
Appliance
Power
(W)
Current
(A)
Fuse
(3A,5A,13A)
kettle
2300 TV
600
iron
1200
lamp
150
cooker
1800
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13. flippedaroundphysics.com 2016
A hairdryer doesn’t have an earth wire.
Can you think why not?
It is made of plastic. Therefore, the casing
can’t become live.
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14. flippedaroundphysics.com 2016
Such appliances have this symbol.
They are “double insulated”
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15. flippedaroundphysics.com 2016
Circuit Breakers
switch
electromagnet
Can you work out how they work?
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