# Physics

ELECTRICITY

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• Created by: Hannah
• Created on: 14-04-11 19:28

## MAINS ELECTRICITY (PLUGS)

• An electrical cable contains three wires
• These wires are made of copper as they are a good conductor
• Each wire is encased in plastic because ths is a good insulator
• Pins in the plug are made of brass as this is a good conductor and is hard

Because of the neutral and live wre mains electricity has an alternating current (ac). The current changed direction 50 tmes per second (50Hz). Mains electricity in the UK is about 230 volts.

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## NEUTRAL WIRE

(BLUE)- completes the circuit, it is kept at zero volts by the electricity company

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## LIVE WIRE

(BROWN)- carries a current that alternates between a positive and negative                             voltage

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## EARTH WIRE

(GREEN & YELLOW)- is there for the safety, it makes an appliance safer to touch                                       if there is a fault by earthing the appliance

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## FUSES

WHAT ARE THEY?- A thin metal wire

WHAT DO THEY DO?- The wire melts if the current is too high, breaking the                                                circuit so no more current can flow through the appliance

WHAT IS THE POINT OF THEM?- Fuses prevent appliances from being damaged                                                         by surges in electricity, they warn owners of                                                               faults and help prevent fires

The correct fuse for an appliances is the one wth the current rating closest to and above the working current of the appliance..

e.g. an appliance wth a current (A) of 10.9 wll need a fuse wth a current rating of           13A

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## HOW EARTH WIRES WORK

Appliances wth a metal casing need an earth wire. If the live wre comes loose and touches the casing and then you touch the casing you wll get a shock.The earth wire prevents this by redirecting the current from the casing to the earth, because this is the lowest resistance path and then the fuse blows because of the large current, and so prevents the shock.

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