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Domestic electricity - Coggle Diagram
Domestic electricity
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The National Grid
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High current means you will lose a lot of energy as the wires heat up and energy is transferred to the surroundings
It is much cheaper to boost the pd really high and keep the current fairly low, thinner wires can also be used which are cheaper
For a given power, increasing the pd decreases the current
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Mains electricity
Ac and Dc
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UK domestic supply is ac, and has a potential difference of around 230V.
The frequency is 50Hz, which means the current alternates between positive and negative 50 times a second
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Each wire has a copper core, because copper is a good conductor of electricity. They are also coated in plastic, because plastic is a good insulator
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The earth wire
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Usually doesn't carry any current, unless there is a fault in the appliance
earthing
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Large current heats and melts to fuse wire, breaking the circuit
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Since the circuit is no longer complete, there is no chance of an electric shock
RCCBs
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If there is a difference in current between the wires, the iron rocker will disconnect, stopping current from flowing
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Doesn't need to be replaced like a fuse, it can be reset
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Fuses
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1) If a fault occurs causing a low resistance route to earth, a large current would flow.
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Double insulation
Metal cased appliances can be dangerous because metal is a good conductor, an alternative is to use double insulation
By adding plastic layer, it means that any surface metal parts can never come into contact with internal parts
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Oscilloscopes
The amplitude of the wave represents the voltage, positive and negative
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Faults
The live wire
If you touch the live wire, a large pd is produced since the live carries 230V and your body is at 0v
A large current will flow through you, which causes and electric shock which could kill you
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The earth wire
Appliances with metal cases can be very dangerous if they come into contact with the live wire, since metal is a good conductor of electricity
The earth wire is attatched to a metal case, which is connected to a metal rod in the ground. If a large current flows to earth, the fuse will melt and stop current from flowing